Resistance Relapse Research Articles

Clinical impact of CA-125 ELIMination rate constant K (KELIM) on surgical strategy in advanced serous ovarian cancer patients

ObjectivesThe modeled CA-125 elimination constant K (KELIM) is a pragmatic early marker of tumor chemosensitivity in ovarian cancer patients treated with neoadjuvant chemotherapy before interval surgery. The primary objective of...

Hypoxia and ERα Transcriptional Crosstalk Is Associated with Endocrine Resistance in Breast Cancer.

Simple SummaryHormone receptor positive breast cancer patients are treated with anti-hormone molecules as a standard of care. However, resistance frequently occurs, leading to hormone resistant metastatic relapses in foreign organs. Understanding the molecular mechanisms through which breast cancer cells evade therapeutic pressure is of paramount interest. Hypoxia, which refers to oxygen deprivation and is characterized by the activation of hypoxia inducible factors, is a common feature of the solid tumor microenvironment, yet its influence on estrogen receptor alpha activity remains elusive. Here, we investigate the consequence of hypoxia and the signaling of hypoxia inducible factors on hormone responsiveness in breast cancer cells and its clinical implications.Estrogen receptor-alpha (ERα) is the driving transcription factor in 70% of breast cancers and its activity is associated with hormone dependent tumor cell proliferation and survival. Given the recurrence of hormone resistant relapses, understanding the etiological factors fueling resistance is of major clinical interest. Hypoxia, a frequent feature of the solid tumor microenvironment, has been described to promote endocrine resistance by triggering ERα down-regulation in both in vitro and in vivo models. Yet, the consequences of hypoxia on ERα genomic activity remain largely elusive. In the present study, transcriptomic analysis shows that hypoxia regulates a fraction of ERα target genes, underlying an important regulatory overlap between hypoxic and estrogenic signaling. This gene expression reprogramming is associated with a massive reorganization of ERα cistrome, highlighted by a massive loss of ERα binding sites. Profiling of enhancer acetylation revealed a hormone independent enhancer activation at the vicinity of genes harboring hypoxia inducible factor (HIFα) binding sites, the major transcription factors governing hypoxic adaptation. This activation counterbalances the loss of ERα and sustains hormone-independent gene expression. We describe hypoxia in luminal ERα (+) breast cancer as a key factor interfering with endocrine therapies, associated with poor clinical prognosis in breast cancer patients.

Cytotoxic effects of aptamer-doxorubicin conjugates in an ovarian cancer cell line

Despite medical advances in treatment strategies over the past 30-years, epithelial ovarian cancer (EOC) continues to be defined by poor patient survival rates and aggressive, drug resistant relapse. Traditional approaches to cancer chemotherapy are typically limited by severe off-target effects on healthy tissue and aggressive drug-resistant recurrence. Recent shifts towards targeted therapies offer the possibility of circumventing the obstacles experienced by these treatments. While antibodies are the pioneering agents in such targeted therapies, several intrinsic characteristics of antibodies limits their clinical translation and efficacy. In contrast, oligonucleotide chemical antibodies, known as aptamers, are ideal for this application given their small size and lack of immunogenicity. This study explored the efficacy of a DNA aptamer, designed to target a well-established cancer biomarker, EpCAM, to deliver a chemotherapeutic drug. The results from this study support evidence that EpCAM aptamers can bind to epithelial ovarian cancer; and offers a valid alternative as a targeting ligand with tuneable specificity and sensitivity. It also supports the growing body of evidence that aptamers show great potential for application-specific, post-SELEX engineering through rational modifications. Through in vitro assays, these aptamers demonstrated cytotoxicity in both monolayer and tumoursphere assays, as well as in tumourigenic enriching assays. Further experimentation based on the results achieved in this project might aid in the development of novel cancer therapeutics and guide the novel designs of drugs for targeted drug delivery.

Abstract 3789: Mapping lesion specific response and relapse patterns in metastatic colorectal cancer patients

Abstract Considerable lesion-specific response heterogeneity exists in metastatic colorectal cancer patients, largely due to organ-specific ecological environments and evolutionary pressures. Metastatic lesions with poor response to therapy often become tumor sanctuary sites, leading to systemic resistance and tumor relapse. To map the lesion-specific response and relapse patterns, we investigated the longitudinal dynamics of individual lesions in metastatic colorectal cancer patients. Tumor longitudinal data in 4,308 colorectal cancer patients with 40,612 individual lesions were collected from eight Phase III trials in Project Data Sphere. First, tumor response dynamics (regression after treatment and progression upon resistance) were characterized using an empirical mathematical model. Next, tumor response time (when the lesion size decreases ≥20% from baseline) and relapse time (when the lesion size increases ≥30% from tumor nadir) were estimated for each individual lesion in patients being treated with bevacizumab, panitumumab, and/or chemotherapy. Random effect cox proportional models were applied to predict lesion-specific response and relapse probabilities and temporal sequence. We then took machine learning algorithm k-means to cluster patients based on their lesion relapse sequence. We found the response probabilities across organs are: Liver > Distal Lymph Nodes (LN) > Abdomen > Spleen > Lung > Regional LN > Adrenal > Muscle/Soft Tissue > Bone > Brain/CNS. Lesion relapse temporal sequence are: Brain/CNS > Liver > Adrenal > Muscle/Soft tissue > Abdomen > Bone > Spleen > Lung > Distal LN > Regional LN. Of note, lesions in the bone, brain, adrenal, and muscle/soft tissues often had low responses and high relapse probabilities, implying the greatest potential as tumor sanctuary sites. Liver, the most common metastatic organ in colorectal cancer, showed highest response rate but high relapse probabilities. Interestingly, the organ-specific response rate and relapse probabilities are respectively in line with drug distribution profiles and organ-specific immune landscape. Organ-specific relapse sequence in each patient is significantly correlated with patient long-term survival (p<0.0001). Patients with relapse lesions occurring in multiple organs had worst survival. Patients whose liver lesions relapsed first had worse survival than those who first relapsed in other organs. In conclusion, our study provides insights into the lesion-specific response and relapse heterogeneity in metastatic colorectal cancer, and yields substantial implications for designing lesion-specific therapeutics. Citation Format: Jiawei Zhou, Quefeng Li, Amber Cipriani, Yanguang Cao. Mapping lesion specific response and relapse patterns in metastatic colorectal cancer patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3789.

Abstract 3833: The role of chemotherapy-induced fibrosis in the maintenance of tumor initiating cells

Abstract Around 80 percent of high-grade serous ovarian cancer patients will relapse with chemotherapy resistant disease. Despite extensive research and developments in immunotherapy, there are limited improvements in overall survival for these patients. Recent research has found that the tumor microenvironment (TME) plays a crucial role in tumor initiation, therapy resistance, and tumor relapse. The TME, which consists of immune cells, blood vessels, and an extracellular matrix (ECM) built primarily by fibroblasts, may enhance the survival and growth of tumor-initiating cells (TICs), chemoresistant stem-like cells thought to be responsible for tumor relapse. Cytotoxic chemotherapies have been shown to modify the TME and this modulation may favor the survival of TICs. For example, carboplatin can activate stromal cells such as fibroblasts to secrete an altered ECM profile, including increases in collagen 1a1 and fibronectin production, which can bind specific integrins upregulated in TICs. Using ex-vivo decellularized peritoneum tissues from mice exposed to chemotherapy or vehicle treatment, we observed a 2-fold increase in growth in peritoneums pre-exposed to chemotherapy relative to those pre-exposed to vehicle. We hypothesize that alterations in the ECM following chemotherapy treatment permit TIC adhesion and growth. To investigate this, mouse embryonic fibroblasts (3T3s) were exposed to chemotherapy during ECM production, decellularized, and reseeded with a panel of ovarian cancer cell lines. Our results suggest a significant increase in cell survival in matrices pre-exposed to chemotherapy compared to control matrices pre-exposed to vehicle. Using this model, we are examining the features of cells that preferentially survive on these matrices. In addition to drug resistance, we are using flow cytometry to assess TIC markers, such as CD117, and CD133, and qRT-PCR to measure stemness genes such as SOX2, OCT4, and NANOG. These studies highlight the need for further investigation into the systemic effects of chemotherapies on the TME and how these changes may be fostering cancer cell adhesion, growth, and survival. Understanding these mechanisms will allow us to develop therapies to achieve better clinical outcomes. Citation Format: Omar Lujano-Olazaba, Mikella Robinson, Samuel F. Gilbert, Emily Kogan, Carrie D. House. The role of chemotherapy-induced fibrosis in the maintenance of tumor initiating cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3833.

Abstract 3163: PR/STAT3 nuclear transcriptional complexes mediate aurora-A kinase-induced stemness plasticity in ER+ breast cancer

Abstract Purpose: Emergence of de novo or acquired resistance to standard of care endocrine therapies represents a major challenge in the clinical management of estrogen receptor alpha positive (ER+) breast tumors. This process is characterized by high tumor plasticity that confers to cancer cells the ability to shift from a differentiated state, with limited tumorigenic potential, to an undifferentiated state which is responsible for drug resistance and tumor relapse. In ER+ breast tumors, this plasticity is manifest by the enrichment of breast tumor initiating cells (BTICs) with stemness features, such as self-renewal capacity, CD44 expression and high ALDH activity, and ER down-regulation. Development of clinically relevant ER+ breast tumor models to test novel therapeutic strategies that inhibit the enhanced tumor cell plasticity and restore or extend endocrine sensitivity are urgently needed. Experimental Design: Unique endocrine resistant and metastatic breast cancer models were utilized to define in vitro and in vivo the pivotal role of Aurora-A mitotic kinase (AURKA) in the induction of stemness plasticity, endocrine therapy resistance and tumor progression. Unbiased phospho-proteomic analysis was performed in the absence or presence of alisertib, a clinically relevant AURKA inhibitor, that was used to identify novel down-stream targets of AURKA signaling pathway. Results: Phospho-proteomic analysis showed that AURKA targeting reduced the phosphorylation of STAT3 transcription factor at the serine-727 site. Significantly, herein we define a novel mechanism by which AURKA-induced self-renewal capacity is mediated through the activation of a phosphorylated serine727-STAT3/serine294-progesterone receptor (PR) transcriptional complex that regulates the expression of KLF4 stemness reprogramming gene. Remarkable, pharmacologic and genetic targeting of AURKA/STAT3/PR oncogenic axis impairs self-renewal capacity of endocrine therapy resistant breast cancer cells. Conclusions: In this study we demonstrate the pivotal role of a novel AURKA/STAT3/PR oncogenic axis in promoting stemness plasticity and endocrine therapy resistance. These findings provide the strong preclinical rationale for the development of novel combinatorial therapeutic strategies targeting cooperative AURKA/serine727-STAT3 and serine294-PR pathways predicted to result in the selective eradication of CD44High/ALDHHigh BTICs from the bulk tumor with consequent benefits to the clinical outcomes of patients with advanced ER+ breast cancer refractory to standard of care endocrine therapy. Citation Format: Antonino B. D'Assoro. PR/STAT3 nuclear transcriptional complexes mediate aurora-A kinase-induced stemness plasticity in ER+ breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3163.

Abstract 3901: Modeling and deciphering COJEC resistance in high risk neuroblastoma

Abstract Neuroblastoma (NB) is a pediatric cancer of the sympathetic nervous system that accounts for 15% of childhood cancer deaths. High-risk (HR) NB tumors are treated with an aggressive multimodal therapy, including the COJEC induction protocol which is a combination of five different chemotherapeutic agents. However, around 15% of primary tumors are refractory from the start and over 60% present treatment resistant relapses. In this project we aim to decipher the mechanisms involved in treatment resistance in HR-NB. Using various NB patient-derived xenograft (PDX) models we designed and tested a clinically-relevant protocol that mimics COJEC treatment and surgical resection. RNA-sequencing, SNP analysis, and histology, were used to explore the molecular mechanisms involved in treatment response. With our COJEC-like protocol we were able to replicate the original patient response in our PDX models. NB PDX1 presented upfront progression and a lack of morphological differentiation. At a molecular level it was characterized by genome duplication and high number of chromosomal aberrations, as well as a high expression of early development/mesenchymal and cell cycle genes. In contrast, NB PDX3 presented an overall good response, leading to a 22% relapse rate after surgery. Relapsed tumors displayed high expression of early development/mesenchymal genes, similar to those seen in refractory PDX1. Meanwhile, the PDX3 tumors collected during surgery that did not relapse (cured) showed low MYCN expression, downregulation of cell cycle and DNA repair genes, along with a strong upregulation of nervous system/nor-adrenergic genes. These genetic signatures derived from the cured PDX3 samples also correlated with good prognosis in large cohorts of HR-NB patients. Despite observing a convergent/parallel evolution of specific genetic aberrations across our PDXs, their presence or absence does not predict prognosis. Instead, the high RNA expression levels of those specific genes correlates with treatment response both in our PDX models and in patient cohorts. Finally, we established 3D tumor organoids derived from treated PDX tumors and confirmed they maintain the molecular characteristics of the parental tumor as well as the acquired COJEC resistance and the tumorigenic capacity, making them an excellent tool to test novel therapeutics against HR-NB. In conclusion, we designed a clinically-relevant COJEC-like protocol that can mimic patient response in PDX models. Early developmental gene signatures appear to correlate with treatment resistance in HR-NB, while the expression of nor-adrenergic signatures after chemotherapy are associated with good prognosis, independently of the accumulation of copy number aberrations. Based on our results, we propose that a combination of DNA and RNA analysis at the surgical resection time point after COJEC could be of clinical interest to evaluate COJEC treatment response and predict future relapses. Citation Format: Adriana Mañas, Kristina Aaltonen, Natalie Andersson, Karin Hansson, Alexandra Seger, Hiroaki Yasui, Katarzyna Radke, Javanshir Esfandyari, David Lindgren, David Gisselsson, Daniel Bexell. Modeling and deciphering COJEC resistance in high risk neuroblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3901.

Omega-3 fatty acids decrease CRYAB, production of oncogenic prostaglandin E2 and suppress tumor growth in medulloblastoma

AimsMedulloblastoma (MB) is one of the most common malignant central nervous system tumors of childhood. Despite intensive treatments that often leads to severe neurological sequelae, the risk for resistant relapses remains significant. In this study we have evaluated the effects of the ω3-long chain polyunsaturated fatty acids (ω3-LCPUFA) docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) on MB cell lines and in a MB xenograft model. Main methodsEffects of ω3-LCPUFA treatment of MB cells were assessed using the following: WST-1 assay, cell death probes, clonogenic assay, ELISA and western blot. MB cells were implanted into nude mice and the mice were randomized to DHA, or a combination of DHA and EPA treatment, or to control group. Treatment effects in tumor tissues were evaluated with: LC-MS/MS, RNA-sequencing and immunohistochemistry, and tumors, erythrocytes and brain tissues were analyzed with gas chromatography. Key findingsω3-LCPUFA decreased prostaglandin E2 (PGE2) secretion from MB cells, and impaired MB cell viability and colony forming ability and increased apoptosis in a dose-dependent manner. DHA reduced tumor growth in vivo, and both PGE2 and prostacyclin were significantly decreased in tumor tissue from treated mice compared to control animals. All ω3-LCPUFA and dihomo-γ-linolenic acid increased in tumors from treated mice. RNA-sequencing revealed 10 downregulated genes in common among ω3-LCPUFA treated tumors. CRYAB was the most significantly altered gene and the downregulation was confirmed by immunohistochemistry. SignificanceOur findings suggest that addition of DHA and EPA to the standard MB treatment regimen might be a novel approach to target inflammation in the tumor microenvironment.

Mechanistically Coupled PK (MCPK) Model to Describe Enzyme Induction and Occupancy Dependent DDI of Dabrafenib Metabolism.

Dabrafenib inhibits the cell proliferation of metastatic melanoma with the oncogenic BRAF(V600)-mutation. However, dabrafenib monotherapy is associated with pERK reactivation, drug resistance, and consequential relapse. A clinical drug-dose determination study shows increased pERK levels upon daily administration of more than 300 mg dabrafenib. To clarify whether such elevated drug concentrations could be reached by long-term drug accumulation, we mechanistically coupled the pharmacokinetics (MCPK) of dabrafenib and its metabolites. The MCPK model is qualitatively based on in vitro and quantitatively on clinical data to describe occupancy-dependent CYP3A4 enzyme induction, accumulation, and drug–drug interaction mechanisms. The prediction suggests an eight-fold increase in the steady-state concentration of potent desmethyl-dabrafenib and its inactive precursor carboxy-dabrafenib within four weeks upon 150 mg b.d. dabrafenib. While it is generally assumed that a higher dose is not critical, we found experimentally that a high physiological dabrafenib concentration fails to induce cell death in embedded 451LU melanoma spheroids.

IL-6 promotes drug resistance through formation of polyploid giant cancer cells and stromal fibroblast reprogramming

To understand the role of polyploid giant cancer cells (PGCCs) in drug resistance and disease relapse, we examined the mRNA expression profile of PGCCs following treatment with paclitaxel in ovarian cancer cells. An acute activation of IL-6 dominated senescence-associated secretory phenotype lasted 2–3 weeks and declined during the termination phase of polyploidy. IL-6 activates embryonic stemness during the initiation of PGCCs and can reprogram normal fibroblasts into cancer-associated fibroblasts (CAFs) via increased collagen synthesis, activation of VEGF expression, and enrichment of CAFs and the GPR77 + /CD10 + fibroblast subpopulation. Blocking the IL-6 feedback loop with tocilizumab or apigenin prevented PGCC formation, attenuated embryonic stemness and the CAF phenotype, and inhibited tumor growth in a patient-derived xenograft high-grade serous ovarian carcinoma model. Thus, IL-6 derived by PGCCs is capable of reprogramming both cancer and stromal cells and contributes to the evolution and remodeling of cancer. Targeting IL-6 in PGCCs may represent a novel approach to combating drug resistance.

733P Bevacizumab (Bev), olaparib (Ola) and durvalumab (Durva) in patients with recurrent advanced ovarian cancer (AOC): The GINECO BOLD study

In high-grade AOC patients, the combination of immunotherapy, PARP inhibitors (PARPi), and antiangiogenic agents, may enhance the efficacy of each treatment. Different chemotherapy-free combinations were previously found to be feasible. A significant activity of the Durva + Ola +/- Bev combination was reported in platinum-sensitive recurrent (PSR) AOC in the MEDIOLA trial. However the efficacy of the triplet in platinum resistant relapse (PRR) has never been assessed.

823TiP Fluzoparide combined with apatinib mesylate in the treatment of platinum resistant recurrent ovarian cancer: A single arm, single center, prospective clinical study

Ovarian cancer is one of the most common malignant tumors in female genital organs. The incidence rate is third highest and its mortality is the highest. In the treatment of ovarian cancer, 70% of patients will still relapse after chemotherapy, of which, about 25% isplatinum resistant relapse, which seriously affects the quality of life and prognosis of patients. At present, platinum-resistant ovarian cancer treatment is still a difficult problem. BRCA gene mutation is closely related to the occurrence and development of ovarian cancer.

Molecular features and vulnerabilities of recurrent chordomas

BackgroundTumor recurrence is one of the major challenges in clinical management of chordoma. Despite R0-resection, approximately 50% of chordomas recur within ten years after initial surgery. The underlying molecular processes are poorly understood resulting in the lack of associated therapeutic options. This is not least due to the absence of appropriate cell culture models of this orphan disease.MethodsThe intra-personal progression model cell lines U-CH11 and U-CH11R were compared using array comparative genomic hybridization, expression arrays, RNA-seq, and immunocytochemistry. Cell line origin was confirmed by short tandem repeat analysis. Inter-personal cell culture models (n = 6) were examined to validate whether the new model is representative. Cell viability after HOX/PBX complex inhibition with small peptides was determined by MTS assays.ResultsUsing whole genome microarray analyses, striking differences in gene expression between primary and recurrent chordomas were identified. These expression differences were confirmed in the world’s first intra-personal model of chordoma relapse consisting of cell lines established from a primary (U-CH11) and the corresponding recurrent tumor (U-CH11R). Array comparative genomic hybridization and RNA-sequencing analyses revealed profound genetic similarities between both cell lines pointing to transcriptomic reprogramming as a key mechanism of chordoma progression. Network analysis of the recurrence specific genes highlighted HOX/PBX signaling as a common dysregulated event. Hence, HOX/PBX complexes were used as so far unknown therapeutic targets in recurrent chordomas. Treating chordoma cell lines with the complex formation inhibiting peptide HXR9 induced cFOS mediated apoptosis in all chordoma cell lines tested. This effect was significantly stronger in cell lines established from chordoma relapses.ConclusionClearly differing gene expression patterns and vulnerabilities to HOX/PBX complex inhibition in highly therapy resistant chordoma relapses were identified using the first intra-personal loco-regional and further inter-personal chordoma progression models. For the first time, HOX/PBX interference was used to induce cell death in chordoma and might serve as the basic concept of an upcoming targeted therapy for chordomas of all progression stages.

Epigenetic Drugs Selectively Target a Population of AML Cells Which Are Positive for CD123 Cell Surface Marker and Are Chemoresistant

Acute Myeloid leukemia (AML) is the most common acute leukemia in adults. While Cytarabine (Ara-C) based chemotherapy has been a standard for initial treatment, over 50% of patients will eventually relapse within a period of time. Chemoresistance remains a major burden for treatment of relapse patient. Recent studies suggest that AML relapse is caused by the survival of drug resistant leukemia stem cell (LSC) population. Since LSCs are in low frequency and remain quiescent in patients, it is difficult to study the chemoresistant mechanism on this population of cells. It has been previously shown that cell lines that derived from patient sample might be considered as attractive models aimed to better characterize LSC biological properties and their chemotherapy resistance mechanisms. Multiple LSC cell surface markers has been identified in patient sample and cell lines. However, it remains to be determined whether subpopulations with different LSC markers has similar level of chemoresistance.To better understand the mechanism of drug resistance and whether it is correlated to the expression of certain group of LSC surface markers, we collected various human AML cell lines and examined correlations of their IC50 of Ara-C and percentage of individual LSC surface markers in these cell lines. We found that CD34 surface marker is not correlated to chemoresistance. Other LSC surface markers, such as CD13, CD44, CD117, CD96 and CD45RA are also not correlated to chemoresistance. Interestingly, CD47 (R square = 0.6660, P value = 0.0476) and CD 123 (R square = 0.7421, P value = 0.0275) are positively correlated to chemoresistance. In order to rule out heterogeneous genetic background contribute to chemoresistance of cell lines, we generated a drug resistant cell line from an drug sensitive AML cell line, OCI-AML2, by gradually increased the Ara-C concentration in culture media. During the selection, the percentage of cells with CD47 and CD123 gradually increased. When the resistant cell line is established, the percent of CD123 positive cells are over 90 percent. Through cell tracking experiments, we found that resistant cells grow at least two cycles slower than sensitive cells in a 5 day tracking assay. RNAseq analysis shows that genes related to cell cycle regulator and resistance of apoptosis changed significantly. However, genes that related to stemness, such as Oct4, Nanog, KLF4, Myc, FLT3, are no significant changed in drug resistant cells compare with the sensitive line, although Sox2 increased 50% and ALDH1A3 increased 3 folds. Therefore, chemoresistant cells may represent cells in a slow growing, de-differentiate stage, however, it may not bare all characteristics of a LSC.We further investigate the role of epigenetic factors in regulating the survival of chemoresistant leukemia cells. Our data shows epigenetic drugs that targeting histone deacetylases, bromodomain proteins and PRC1 complex are effective to induce apoptosis and cell death of chemoresistant cells, therefore they may be potential second line of chemotherapy drug for chemoresistant patients. Histone deacetylase inhibitor Romidepsin efficiently cleared chemoresistant AML blast in xenographed NSG mice. Furthermore, we found Romidepsin has synergetic effect when combine with Ara-C. Interestingly, Romedepsin preferentially target CD123 positive, slow growing cells while Ara-C mainly target fast growing, CD123 negative cells. Therefore, combine treatment with Romedepsin and Ara-C may prevent the development of chemoresistance in AML cells. In summary, we identify CD123 and CD47cell surface markers may potentially serve as biomarker for chemresistance AML cells. Our study also sheds light on a new mechanism of drug resistance in leukemia, and provide a rationale to develop and test epigenetic-targeted therapies in leukemia, especially in drug resistant relapse patients. DisclosuresNo relevant conflicts of interest to declare.

Comparative evaluation of the effectiveness of primary treatment regimens in patients with classical Hodgkin’s lymphoma from the group of unfavorable prognosis

Objective. Comparative evaluation of the effectiveness and toxicity profile of intensified chemotherapy regimens BEACOPP escalated (esc.), BEACOPP-14 and EACOPP‑14 in primary patients with classical Hodgkin’s lymphoma of an unfavorable prognostic group.Materials and methods. The study included 149 patients: 84 women (56 %) and 65 men (44 %) with a newly diagnosed classic Hodgkin’s lymphoma, who received antitumor treatment in the Department of high-dose chemotherapy with a bone marrow transplantation unit at the Р. A. Hertzen Moscow Oncology Research Institute from 2006 to 2018. The median age was 31 years (17–69). The majority of patients were diagnosed with Hodgkin’s lymphoma nodular sclerosis (88.6 %). All patients belonged to an unfavorable prognostic group, despite the fact that more than 1/3 of them had local stages of the disease. The most frequent adverse factors identified in the majority of patients were: massive lymph node lesion (bulky disease) – in 111 patients (74.5 %), B-symptoms – in 84 (56.4 %), increased erythrocyte sedimentation rate – in 55 (36.9 %), extranodal lesion – in 105 (70.5 %), including bones and bone marrow – in 10 (6.7 %) and 14 (9.4 %), respectively. Antitumor treatment was performed under the BEACOPP program in the following modifications: BEACOPP‑14 – 94 (63.1 %), EACOPP-14 – 32 (21.5 %), BEACOPP-esc. – 23 patients (15.4 %). Consolidating radiotherapy was performed in the majority of patients – 132 (88.6 %).Results. After the chemotherapy, remission of the disease was achieved in 141 patients (94.6 %), a complete response was in 101 of them (67.8 %). The immediate antitumor effect was more expressed when using the program BEACOPP‑14 (in 72.3 %), compared to EACOPP‑14 and BEACOPP-esc. (in 59.4 % and 60.9 %, respectively).Chemotherapy resistance was observed in 8 patients (5.4 %). Chemotherapy results were improved in combination with radiation therapy in 40 patients (26.8 %). After the end of chemoradiotherapy, complete remissions were achieved in more than 93.6 % of patients. Relapses occurred in 8 patients: early – in 3 (2.1 %) and late – in 5 (3.5 %). Four patients died (2.7 %): 1 – from disease progression, 2 – from resistant relapse, and 1 patient from other causes.With a median follow-up of 46 months, the 5-year overall survival rate was more than 93.7 %, event-free-more than 83 %, and relapse-free – 90.3 % or more. When evaluating long-term treatment results depending on the induction chemotherapy program, the outcome was better when using the BEACOPP-esc. in comparison with EACOPP‑14 and BEACOPP‑14. The most frequent myelotoxic complication – more than 90 % – on all chemotherapy programs was deep leukopenia. Thrombocytopenia III–IV degree developed more often on the BEACOPP-esc. (in 52.2 %), severe anemia – on EACOPP‑14 (in 44 %). Among infectious complications, mucositis prevailed and was most often observed on BEACOPP-esc. (in 74 %). Febrile neutropenia and herpetic infection developed less frequently, mainly in the BEACOPP-esc. and EACOPP‑14 program. Another serious complication was pneumonia, which was more frequently reported during BEACOPP‑14 (18.1 %). Secondary tumors, as a later complication, were less likely to be detected in the treatment program BEACOPP‑14 (1 %), compared to BEACOPP-esc. and EACOPP-14 (4.3 % and 3.1 %, respectively).Conclusion. All modifications of the BEACOPP program showed good direct effectiveness. However, the best long-term results, despite slightly more expressed toxicity, were noted on the BEACOPP-esc. program.

Abstract PS16-19: Hotspot p53 mutations correlate with increased expression of stem cell markers in triple-negative breast cancer

Abstract p53 mutations occur in 80% of triple-negative breast cancer (TNBC) cases. Several types of p53 mutations have been reported, among which gain of function mutations have been associated with increased cancer stem cells, chemotherapy resistance, and disease relapse in several malignancies. Particularly, hotspot p53 mutations (mutations at amino acid location 157, 175, 248, 249, 273 predict worse overall survival in some cancer types. We have previously reported that Ganglioside GD2, a cell surface glycosphingolipid, identifies breast cancer stem cells and promotes tumorigenesis. We have also reported that GD3 synthase, a key enzyme which catalyzes the rate-limiting step of the GD2 biosynthesis pathway, is significantly upregulated in breast tumors with p53 mutations. Here, we hypothesize that mutant p53 promotes stemness in TNBC cells by regulating GD3 synthase and GD2 expression. To identify specific p53 mutations that contribute to TNBC stemness, we stratified TNBC cell lines (N=18) based on p53 mutation status including mutation type, location, and domain affected. We measured GD2 and GD3 synthase expression in the available TNBC cell lines by flow cytometry and RT-PCR, respectively. We found that GD3 synthase expression is significantly upregulated in TNBC cell lines with p53 hotspot mutations compared to cell lines with other p53 mutations (Median relative expression 0.0114 compared to 0.0003, p=0.005). Similarly, we found that GD2 expression is significantly higher in TNBC cell lines with hotspot mutations compared to non-hotspot counterparts (Median GD2+ cells 15.2% compared to 0.97%, p= 0.013) Additionally, GD2 and GD3 synthase are upregulated in basal-type TNBC cell lines and TCGA patient samples compared to other TNBC molecular subtypes. Interestingly, we also found that GD2 expression is not always directly correlated with GD3S expression, suggesting that GD2 synthase expression is also a key factor in the regulation of GD2 expression. To examine the effect of mutant p53 protein levels on TNBC stemness, we measured p53 expression in all the available TNBC cell lines by western blot, and found that p53 protein levels do not correlate with GD2 or GD3S expression. To validate these findings, we analyzed RPPA data from the MD Anderson Cancer Cell Lines Project and found similar results. These data suggest that it is the type of p53 mutation, but not the amount of p53 protein in the cells that determines GD2 and GD3 synthase expression in TNBC cells. For instance, p53 hotspot mutations involving amino acid position 248 have been shown to be strongly associated with increased cancer stemness. We found that cell lines with p53 mutations at this specific location have significantly higher GD3 synthase expression compared to other mutant p53 forms. We are currently examining the direct role of mutant p53 in the regulation of GD3S expression by stabilizing mutant p53 using MDM2 inhibitors as well as stable knockdown of p53 gene in multiple TNBC cell lines to establish a clear link between mutant p53 and stem cell marker expression in TNBC cell lines. In conclusion, stem cell markers are highly expressed in p53 mutant TNBC cell lines compared to wild type p53 counterparts. Specifically, cell lines with hotspot p53 mutations significantly correlate with increased TNBC stemness. The type of p53 mutation, rather than level of its expression correlates with stem cell marker expression in TNBC cells. Citation Format: Fouad El-Dana, Bin Yuan, Stanley Ly, Vivek Anand, Venkata Lokesh Battula. Hotspot p53 mutations correlate with increased expression of stem cell markers in triple-negative breast cancer [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS16-19.

Abstract PO049: Compartment-specific profiling for evaluation of disrupted signaling in early stage, low-grade endometrial cancer

Abstract Understanding tumor microenvironment is critical to improving conservative management (non-surgical) strategies for early stage, low grade endometrial cancer (EC). This remains an unmet clinical need for women who wish to maintain fertility and those who cannot undergo surgery due to medical co-morbidities. Current regimens rely on progestin treatment, but resistance and early relapse require improved therapeutic strategies. We sought to evaluate alterations in gene expression in the epithelial and stromal compartment of EC compared to normal endometrium to identify targets for combination therapies. RNA was extracted from microdissected epithelial and stromal compartments of formalin fixed paraffin embedded early stage, low grade EC and normal endometrium (NE). Comprehensive transcriptome profiling was performed with Affymetrix Clariom D assay and pathway analysis was performed. Immunohistochemistry (IHC) was used for validation. Functional studies of differentially expressed genes were performed in Hec1A EC cell lines. Among differentially expressed genes in EC vs NE, multiple altered signaling pathways were identified. EIF2 signaling, eIF4 and p70S6K signaling, and PI3K/AKT/mTOR were the most significant pathways activated in both epithelial and stromal compartments. In the epithelia compartment, the most significant gene expression changes included reduced expression of RBPMS (RNA Binding Protein with Multiple Splicing), SORD (Sorbitol Dehydrogenase), DDX17 (DEAD-Box Helicase 17), and TPT1 (Translationally-Controlled Tumor Protein) in EC, while MTDH (Metadherin) was significantly increased in EC. Similar changes were observed in the stroma compartment, but with lower fold changes than that observed in gland. Together with decreased RBPMS expression, decreased RBPMS-interacting molecules IGF2, TCF7L2 (Transcription Factor 7 Like 2), FOS (Proto-Oncogene C-Fos) and increased GPS2 (G protein Pathway Suppressor 2) were also observed. Differential expression of proteins in gland and stroma was also confirmed by IHC. An inverse correlation of RBPMS expression and EC proliferation was also observed in EC at the protein level. Enhanced AKT and S6 protein phosphorylation were observed by RBPMS silencing in Hec1A endometrial cells. Reverse Phase Protein Array demonstrated activation of Caveolin 1, FOXO3 (Forkhead Box O3), MT-CO1 (Mitochondrially Encoded Cytochrome C Oxidase I), L1CAM (L1 Cell Adhesion Molecule) with RBPMS silencing in Hec1A cell. These molecules are involved in pathways such as molecular mechanisms of cancer, estrogen receptor signaling, and senescence pathway. While estrogen-regulated changes were prominent in early stage low-grade EC, the identification of additional signaling changes provide support for an ongoing trial of levonorgestrel IUD + everolimus (mTOR inhibitor) and can be probed further to identify new targets for combination conservative management strategies. Additionally, biomarkers from these pathways, such as RBPMS, can be studied to guide the selection of progestin-only therapy versus combination therapy. Citation Format: Qian Zhang, Xiaoping Su, Joseph Celestino, Ying Yuan, Samuel C. Mok, Karen H. Lu, Melinda S. Yates. Compartment-specific profiling for evaluation of disrupted signaling in early stage, low-grade endometrial cancer [abstract]. In: Proceedings of the AACR Virtual Special Conference: Endometrial Cancer: New Biology Driving Research and Treatment; 2020 Nov 9-10. Philadelphia (PA): AACR; Clin Cancer Res 2021;27(3_Suppl):Abstract nr PO049.

Natural Compounds in Sex Hormone-Dependent Cancers: The Role of Triterpenes as Therapeutic Agents.

Sex hormone-dependent cancers currently contribute to the high number of cancer-related deaths worldwide. The study and elucidation of the molecular mechanisms underlying the progression of these tumors was a double-edged sword, leading to the expansion and development of new treatment options, with the cost of triggering more aggressive, therapy resistant relapses. The interaction of androgen, estrogen and progesterone hormones with specific receptors (AR, ER, PR) has emerged as a key player in the development and progression of breast, ovarian, prostate and endometrium cancers. Sex hormone-dependent cancers share a common and rather unique carcinogenesis mechanism involving the active role of endogenous and exogenous sex hormones to maintain high mitotic rates and increased cell proliferation thus increasing the probability of aberrant gene occurrence and accumulation highly correlated with abnormal cell division and the occurrence of malignant phenotypes. Cancer related hormone therapy has evolved, currently being associated with the blockade of other signaling pathways often associated with carcinogenesis and tumor progression in cancers, with promising results. However, despite the established developments, there are still several shortcomings to be addressed. Triterpenes are natural occurring secondary metabolites biosynthesized by various pathways starting from squalene cyclization. Due to their versatile therapeutic potential, including the extensively researched antiproliferative effect, these compounds are most definitely a cornerstone in the research and development of new natural/semisynthetic anticancer therapies. The present work thoroughly describes the ongoing research related to the antitumor activity of triterpenes in sex hormone-dependent cancers. Also, the current review highlights both the biological activity of various triterpenoid compounds and their featured mechanisms of action correlated with important chemical structural features.

Abstract 4143: Identification of molecular targets for conservative management of early stage, low-grade endometrial cancer through compartment-specific transcriptome profiling

Abstract Understanding tumor microenvironment is critical to improving conservative management (non-surgical) strategies for early stage, low grade endometrial cancer (EC). This remains an unmet clinical need for women who wish to maintain fertility and those who cannot undergo surgery due to medical co-morbidities. Current regimens rely on progestin treatment, but resistance and early relapse require improved therapeutic strategies. We sought to evaluate alterations in gene expression in the epithelial and stromal compartment of EC compared to normal endometrium to identify targets for combination therapies. RNA was extracted from microdissected epithelial and stromal compartments of formalin fixed paraffin embedded early stage, low grade EC and normal endometrium (NE). Comprehensive transcriptome profiling was performed with Affymetrix Clariom D assay and pathway analysis was performed. Immunohistochemistry (IHC) was used for validation. Functional studies of differentially expressed genes were performed in EC cell lines, ECC-1 and Hec1A. Focusing on differentially expressed genes in the epithelial compartment of EC vs NE, multiple activated signaling pathways were identified, including eIF2 signaling, eIF4 and p70S6K signaling, PI3K/AKT/mTOR, and hormone signaling. Top gene expression changes with significantly lower expression in EC included RBPMS (RNA-binding protein with multiple splicing), SORD (sorbitol dehydrogenase), DDX17 (DEAD-box helicase 17), and TPT1 (translationally-controlled tumor protein) gene expression, while MTDH (metadherin) was significantly increased in EC. Differential expression of proteins coded by these genes was confirmed by IHC. Additionally, RBPMS silencing enhanced AKT and S6 protein phosphorylation in Hec1A cells and forced expression of RBPMS in ECC-1 cells attenuated Erk1/2 MAP kinase activation. Expression of RBPMS inhibited cell proliferation and knockdown of RBPMS increased proliferation. Treatment of EC cells with everolimus (mTOR inhibitor) resulted in differential inhibition of proliferation based on RBPMS expression. Communication between tumor and stroma is also being evaluated. While estrogen-regulated changes were prominent in early stage low-grade EC, the discovery of alterations in other signaling pathways suggest additional targets for conservative management of the disease. The identification of signaling nodes shared between hormone-regulated pathways and mTOR signaling provides further justification for the ongoing combination therapy trial (progestin plus everolimus). Additionally, biomarkers from these pathways, such as RBPMS, can be studied to guide the selection of progestin-only therapy versus combination therapy. Citation Format: Qian Zhang, Xiaoping Su, Joseph Celestino, Ying Yuan, Samuel C. Mok, Karen H. Lu, Melinda S. Yates. Identification of molecular targets for conservative management of early stage, low-grade endometrial cancer through compartment-specific transcriptome profiling [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4143.

Abstract 4960: Sox2, Oct4, and Nanog expression for identification of ovarian cancer tumor initiating cells

Abstract High Grade Serous Ovarian Cancer (HGSOC) is the most lethal gynecological disease in women, with over 70% of advanced stage disease relapsing within 18 months. Recent studies suggest that tumor-initiating cells (TICs) support tumor heterogeneity, chemoresistance, and relapse in HGSOC. Identification of TICs has traditionally relied on expression of surface markers such as CD133, CD44, and CD117 and/or enzymes such as aldehyde dehydrogenase (ALDH). Unfortunately, these markers are often cell type specific and not reproducible across patient samples. More reliable markers of TICs may include stem cell transcription factors such as Sox2, Oct4, and Nanog that function to support long-term self-renewal, multipotency, and quiescence, although these factors have not been comprehensively evaluated in ovarian cancer. We have previously shown that ovarian cancer cells cultured in 3D spheroid-supporting conditions have enhanced expression of Sox2, Oct4, and Nanog and are more tumorigenic than cells cultured in 2D as a monolayer. We hypothesize that Sox2, Oct4, and Nanog support spheroid formation, chemotherapy resistance, and tumorigenicity more reliably than traditional TIC markers. To investigate this hypothesis we evaluated five HGSOC cell lines (CAOV3/CAOV4/OV90/OVCAR4/OVCAR8), two undefined serous lines (ACI23, OVCAR5) and one non-serous line (SKOV3) in 2D vs 3D conditions and quantitated Sox2, Oct4, and Nanog expression, spheroid formation, chemotherapy resistance and tumorigenicity. Our data show that OVCAR4, OVCAR5, and OVCAR8 had the highest expression of Sox2, Oct4, and Nanog in 3D conditions and at least half of the cell lines had enriched expression of all three factors after chemotherapy treatment. A correlation analysis of the traditional TIC markers shows that the surface marker CD133 positively correlated with expression of Sox2, Oct4, and Nanog. Analysis of TCGA data shows that Sox2, Oct4, and Nanog are prone to amplification or gain of function events in 21%, 4%, and 7% of patients, respectively, and these patients are significantly more likely to have recurrent disease. Overall our findings suggest that Sox2, Oct4, and Nanog correlate with TIC features and may be more reliable markers for the identification of cells with enhanced tumor-initiation capacity and drug resistance. Our data further clarify specific ovarian cancer cell lines that have greater dependence on these factors. More reliable and consistent identification of ovarian TICs will improve our understanding of TIC biology and enable the design of therapies to overcome chemotherapy resistance and disease relapse. Citation Format: Mikella Robinson, Samuel F. Gilbert, Logan J. Alexander, Samuel E. Green, Omar Lujano-Olazaba, Omid Patrus, Jennifer A. Waters, Jacqueline M. Lara, Carrie D. House. Sox2, Oct4, and Nanog expression for identification of ovarian cancer tumor initiating cells [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4960.