Treatment Of Other Malignancies Research Articles

Cardiac Complications of Multiple Myeloma Treatments.

Multiple myeloma (MM) arises in plasma cells, a type of white blood cell. The cancerous plasma cells produce monoclonal immunoglobulins in the bone marrow. The extent of proliferation in the malignant state can manifest in many complications including osteopenia, osteolytic lesions, pathologic fractures, hypercalcemia, anemia, and kidney dysfunction. As is the case with the treatment of other malignancies, the research relating to the management of MM is dynamic and evolving. In this review, we aim to succinctly summarize and categorize the major treatment options of MM, including both new treatments and also older treatments that are now less frequently utilized, with a specific focus on the cardiotoxicity of these agents.

The Proteasome Inhibitor Marizomib Evokes Endoplasmic Reticulum Stress and Promotes Apoptosis in Human Glioblastoma Cells.

Proteasomes play an important role in the physiology of cancer cells, and inhibition of their activity may be used as a promising therapeutic strategy against glioblastoma (GBM). Although certain proteasome inhibitors (PIs) have been approved for the treatment of other malignancies, they have limited effectiveness against GBM due to low brain bioavailability. Marizomib (MZB) is an irreversible, second-generation proteasome inhibitor, which unlike other PIs can penetrate through the blood-brain barrier, making it a promising therapeutic tool in brain malignancies. The antitumor activity of MZB was investigated in LN229 and U118 cells. The MTT test and the ATP-based assay were performed to evaluate cytotoxicity. Flow cytometry analysis was used to determine the apoptotic death of GBM cells. Luminescent assays were used to assess levels of reactive oxygen species (ROS) and the activity of caspase 3/7. RT-qPCR and Western blot analyses were used to determine gene and protein expressions. Marizomib decreased the viability and caused apoptotic death of GBM cells. The proapoptotic effect was accompanied by activation of caspase 3 and overexpression of cl-PARP, Noxa, Cyt C, and DR5. Moreover, treatment with MZB triggered endoplasmic reticulum (ER) stress, as shown by increased expressions of GRP78, IRE1α, p-EIF2α, p-SAPK/JNK, CHOP, ATF6α, and ATF4. On the contrary, overproduction of ROS or increased expressions of ERO1α, LC3 II, Beclin 1, and ATG5 were not detected, suggesting that neither oxidative stress nor autophagy were involved in the process of MZB-induced cell death. Thus, marizomib represents a potentially promising compound for facilitating further progress in brain cancer therapy.

Combination of Venetoclax and Azacytidine As First-Line Induction Therapy for Acute Myeloid Leukemia in Patients Younger Than 60 Years: A Tertiary Care Center Experience from Our Low Middle Income Country

INTRODUCTION: Anthracycline- and cytarabine-based “7+3” induction chemotherapy has been the frontline treatment option for acute myeloid leukemia (AML) in the non-elderly and fit patient population. Sixty percent of these patients (pts) achieve Complete remission (CR). However, an estimated 30-40% of pts relapse (Tara L. Lin & Livio Pagano et al., Expert Review of Hematology, 2021). In addition, based on a large US database study and studies from India, the “7+3” regimen is associated with high rates of induction mortality, intensive care unit (ICU) admission, and duration of hospital stay. BCL2 inhibition with venetoclax has been a new paradigm for the treatment of AML. Herein, we present our institutional experience in treating AML in pts younger than 60 years (yrs) old with a combination of venetoclax (ven) and azacytidine (aza). METHODS: We conducted a retrospective review of patients aged 18-60 who were newly diagnosed with AML between May 2020 and May 2023, and in this study, we included all pts, who met the WHO criteria for AML, did not have APML, had no prior history of treatment for other malignancies, and had not received prior induction treatment. Pts received aza 75 mg/m2 on days 1-7 and ven, which escalated from 100 to 200 to 400 mg on days 1-3. Ven continued at 400 mg without posaconazole or 100 mg with posaconazole from days 4-28, and bone marrow aspiration and biopsy were performed after day 28. Patients who achieved morphological remission without count recovery had up to 14 days off therapy before subsequent cycles. Non-responders received up to 1-2 additional cycles. Post-response (defined as a complete remission [CR] ), and patients with measurable residual disease (MRD) negative by multiparameter flow cytometry (MFC) with the residual blast cutoff being < 0.1% proceeded to further cycles. The primary objective of the study is to focus on the induction mortality rate and complete remission in younger, newly diagnosed AML pts who received aza and ven in the induction period. Responses to induction and subsequent post-remission therapy were recorded. RESULTS: A total of 17 patients with AML aged ≥ 18 years and ≤60 years were treated with a combination of aza and ven from May 2020 to May 2023. The median patient age was 47 yrs (interquartile range [IQR]: 30-56 yrs, 52.9% age <50 yrs ), and 52.9% of the pts were males. According to the European Leukemia Network (ELN) guidelines for 2022, using FISH and next-generation sequencing (NGS), 5 out of 17 pts (41.2%) were categorized as having favorable risk, 3 out of 17 patients (17.6%) were categorized as having intermediate risk, and 9 out of 17 pts (41.2%) were categorized as having adverse risk. During their inpatient stay, none of the pts required renal replacement therapy (RRT), and 1 out of 17 (5.8%) pts required mechanical ventilation. The dose of ven was 400 mg in 8 out of 17 patients (47%). One pt was on sertraline and received 200mg of ven. The remaining pts (8/17) received 100 mg of ven with posaconazole, which reduced the cost of the treatment to 50%. The median pretreatment white cell count (WCC) was 11.49 x 10^9/L (IQR: 6.25 to 39.74 x 10^9/L). The platelet count took a median of 31 days to recover above 50 x 10^9/L (IQR: 28-43 days), while the median time for the absolute neutrophil count (ANC) to recover above 1 x 10^9/L was 52 days (IQR: 47-60 days). 11 out of 17 (64%) of our patients achieved complete remission (CR1) after the first cycle. Additionally, 5 out of 17 (29.4%) were MRD-negative when compared to a large US study database and an Indian study (see table1). The median duration of hospital stay was 16 days (IQR: 10-20 days), and the induction mortality rate was 1/17 (5.8%) (see table1). This death occurred in a patient with adverse risk. CONCLUSIONS: The response to induction therapy with venetoclax and azacytidine in young adults with AML was similar to the standard “7+3” induction therapy, with around 64% of pts achieving CR after the first cycle. The median duration of hospital stay, frequency of ICU admission, and especially induction mortality have been lower than the “7+3” regimen. BCL2 inhibition has indeed resulted in a paradigm shift in the treatment of AML. Therefore, it may be the right time to consider the combination of ven and aza as the standard first-line induction therapy for all pts with AML.

Casein Kinase 2 (CK2): A Possible Therapeutic Target in Acute Myeloid Leukemia.

The protein kinase CK2 (also known as casein kinase 2) is one of the main contributors to the human phosphoproteome. It is regarded as a possible therapeutic strategy in several malignant diseases, including acute myeloid leukemia (AML), which is an aggressive bone marrow malignancy. CK2 is an important regulator of intracellular signaling in AML cells, especially PI3K-Akt, Jak-Stat, NFκB, Wnt, and DNA repair signaling. High CK2 levels in AML cells at the first time of diagnosis are associated with decreased survival (i.e., increased risk of chemoresistant leukemia relapse) for patients receiving intensive and potentially curative antileukemic therapy. However, it is not known whether these high CK2 levels can be used as an independent prognostic biomarker because this has not been investigated in multivariate analyses. Several CK2 inhibitors have been developed, but CX-4945/silmitasertib is best characterized. This drug has antiproliferative and proapoptotic effects in primary human AML cells. The preliminary results from studies of silmitasertib in the treatment of other malignancies suggest that gastrointestinal and bone marrow toxicities are relatively common. However, clinical AML studies are not available. Taken together, the available experimental and clinical evidence suggests that the possible use of CK2 inhibition in the treatment of AML should be further investigated.

Developing Oncolytic Viruses for the Treatment of Cervical Cancer.

Cervical cancer represents one of the most important malignancies among women worldwide. Current therapeutic approaches for cervical cancer are reported not only to be inadequate for metastatic cervical cancer, but are also considered as cytotoxic for several patients leading to serious side effects, which can have negative implications on the quality of life of women. Therefore, there is an urgent need for the development of innovative and effective treatment options. Oncolytic viruses can eventually become effective biological agents, since they preferentially infect and kill cancer cells, while leaving the normal tissue unaffected. Moreover, they are also able to leverage the host immune system response to limit tumor growth. This review aims to systematically describe and discuss the different types of oncolytic viruses generated for targeting cervical cancer cells, as well as the outcome of the combination of virotherapy with conventional therapies. Although many preclinical studies have evaluated the therapeutic efficacy of oncolytic viruses in cervical cancer, the number of clinical trials so far is limited, while their oncolytic properties are currently being tested in clinical trials for the treatment of other malignancies.

Immune checkpoint inhibitors in cholangiocarcinoma.

Cholangiocarcinoma is an epithelial malignancy originating in the biliary tracts and frequently recurs even with surgical resection. Unresectable disease has a 5-year overall survival of less than 10%. Given this poor prognosis, additional therapies are urgently needed. Chemotherapy has been the mainstay of treatment for many years. However, with the incorporation of immunotherapy into the treatment of other malignancies, there has been a great deal of interest in immunotherapy for biliary cancers. Recently, durvalumab was approved in combination with gemcitabine and cisplatin for the treatment of unresectable cholangiocarcinoma in the first-line setting. However, predicting which patients may respond to immunotherapy remains a challenge due to the lack of a reliable biomarker.

Interleukin-15 and chemokine ligand 19 enhance cytotoxic effects of chimeric antigen receptor T cells using zebrafish xenograft model of gastric cancer.

Chimeric antigen receptor (CAR) T cells have been proven effective for the treatment of B-cell-mediated malignancies. Currently, the development of efficient tools that supply CAR T cells for the treatment of other malignancies would have great impact. In this study, interleukin (IL)-15 and C-C motif chemokine ligand 19 (CCL19) were introduced into natural killer group 2D (NKG2D)-based CARs to generate 15×19 CAR T cells, which remarkably increased T-cell expansion and promoted the production of central memory T (Tcm) cells. 15×19 CAR T cells showed greater cytotoxicity to gastric cell lines than conventional CAR T cells and produced higher levels of IL-15 and CCL-19, which resulted in increased responder T cell chemotaxis and reduced expression of T cell exhaustion markers. A live zebrafish model was used for single-cell visualization of local cytotoxicity and metastatic cancers. Administration of 15×19 CAR T cells resulted in significant shrinking of gastric cancer xenograft tumors and expansion of 15×19 CAR T cells in zebrafish models. Taken together, these findings demonstrate that 15×19 CAR T cells are highly efficient in killing gastric cancer cells, are effective to avoid off-target effects, and migrate to local and metastatic sites for long-term surveillance of cancers.

Gastric Cancer and the Immune System: The Key to Improving Outcomes?

Gastric adenocarcinoma is by far the most common form of gastric cancer (GC) and is a highly lethal form of cancer arising from the gastric epithelium. GC is an important area of focus of the medical community, given its often late-stage of diagnosis and associated high mortality rate. While surgery and chemotherapy remain the primary treatments, attention has been drawn to the use of immunologic therapies, which have shown promise in the treatment of other malignancies. The role for immune-based therapies has become clearer as we obtain a greater understanding of the role of the immune system in gastric cancer formation and growth. A variety treatment to augment the immune system are under evaluation in clinical trials, and these include immune checkpoint inhibitors, antibody-drug conjugates, and immune cell-based therapies. Here, we review the immune landscape and immune-based therapies for GC.

Bispecific Antibodies in Prostate Cancer Therapy: Current Status and Perspectives.

Simple SummaryDespite recent advances in treatment, metastasized prostate carcinoma (PC) still has a poor prognosis. Immunotherapy has revolutionized the landscape of cancer therapy, but a breakthrough for PC is missing. The success of immunotherapy in cancers is mostly due to recent strategies to mobilize T cells comprising immune checkpoint inhibition, CAR-T cells and bispecific antibodies (bsAbs). After introducing present approaches and immunotherapy in PC in general, we here review the current clinical development of bsAbs in PC treatment.Prostate carcinoma (PC) is the second most common cancer in men. When the disease becomes unresponsive to androgen deprivation therapy, the remaining treatment options are of limited benefit. Despite intense efforts, none of the T cell-based immunotherapeutic strategies that meanwhile have become a cornerstone for treatment of other malignancies is established in PC. This refers to immune checkpoint inhibition (CI), which generally reinforces T cell immunity as well as chimeric antigen receptor T (CAR-T) cells and bispecific antibodies (bsAbs) that stimulate the T cell receptor/CD3-complex and mobilize T cells in a targeted manner. In general, compared to CAR-T cells, bsAb would have the advantage of being an “off the shelf” reagent associated with less preparative effort, but at present, despite enormous efforts, neither CAR-T cells nor bsAbs are successful in solid tumors. Here, we focus on the various bispecific constructs that are presently in development for treatment of PC, and discuss underlying concepts and the state of clinical evaluation as well as future perspectives.

Abstract PO-044: Epigenetic silencing of SLC17A7 promotes osteosarcoma growth

Abstract Osteosarcoma is an orphan disease with only 900 patients diagnosed each year in US. Most patients are adolescents with small number of older patients. The 5-survival rates for those with metastatic disease is only 30%. Frustratingly, there has been little change in treatment options (chemotherapy, surgery and radiotherapy) due to the difficulty of conducting clinical trials in this rare but deadly cancer. To address this, strong pre-clinical trial information is required to motivate clinical trial design. In vitro and in vivo, we identified that the pan-HDAC inhibitor, panobinostat is highly effective in limiting osteosarcoma growth and metastasis. Panobinostat is approved for the treatment of other malignancies but has noted toxicities. Therefore, to identify therapeutic targets, we explored the HDACs responsible for driving osteosarcoma metastasis and the specific genes through which those HDACs mediated their effects. Our data shows that HDAC1 and HDAC2 are key for osteosarcoma survival using siRNA approaches. Use of the HDAC1/2 selective inhibitor romidepsin in vitro and in vivo supported this finding. To identify targets being regulated by HDAC1/2, we performed microarray and proteomics analyses on romidepsin treated osteosarcoma cells. We found and validated independently that, SLC17A7, a metabolic vesicular glutamate transporter to be highly induced in response to romidepsin treatment; >100 fold more than base line in multiple osteosarcoma cell lines. Functionally, SLC17A7 allows entry of glutamate into the synaptic vesicles from cytoplasm and releases the glutamate from the cells via exocytosis. In our studies, we have seen that romidepsin treatment leads to reduced glutamate levels in the conditioned media and cell death indicating key roles for SLC17A7 in driving osteosarcoma progression and metastasis. In conclusion, our data shows that HDAC1/2 suppression of SLC17A7 is a novel means of promoting osteosarcoma progression and metastasis. Citation Format: Niveditha Nerlakanti, Jeremy McGuire, Diana Yu, Damon R. Reed, Conor C. Lynch. Epigenetic silencing of SLC17A7 promotes osteosarcoma growth [abstract]. In: Abstracts: AACR Special Virtual Conference on Epigenetics and Metabolism; October 15-16, 2020; 2020 Oct 15-16. Philadelphia (PA): AACR; Cancer Res 2020;80(23 Suppl):Abstract nr PO-044.

A Preclinical Embryonic Zebrafish Xenograft Model to Investigate CAR T Cells In Vivo.

Chimeric antigen receptor (CAR) T cells have proven to be a powerful cellular therapy for B cell malignancies. Massive efforts are now being undertaken to reproduce the high efficacy of CAR T cells in the treatment of other malignancies. Here, predictive preclinical model systems are important, and the current gold standard for preclinical evaluation of CAR T cells are mouse xenografts. However, mouse xenograft assays are expensive and slow. Therefore, an additional vertebrate in vivo assay would be beneficial to bridge the gap from in vitro to mouse xenografts. Here, we present a novel assay based on embryonic zebrafish xenografts to investigate CAR T cell-mediated killing of human cancer cells. Using a CD19-specific CAR and Nalm-6 leukemia cells, we show that live observation of killing of Nalm-6 cells by CAR T cells is possible in zebrafish embryos. Furthermore, we applied Fiji macros enabling automated quantification of Nalm-6 cells and CAR T cells over time. In conclusion, we provide a proof-of-principle study that embryonic zebrafish xenografts can be used to investigate CAR T cell-mediated killing of tumor cells. This assay is cost-effective, fast, and offers live imaging possibilities to directly investigate CAR T cell migration, engagement, and killing of effector cells.

Establishment and characterization of patient-derived cancer models of malignant peripheral nerve sheath tumors

BackgroundMalignant peripheral nerve sheath tumors (MPNSTs) are a rare subtype of soft-tissue sarcoma, derived from a peripheral branch or the sheath of the sciatic nerve, brachial plexus, or sacral plexus. The clinical outcomes for MPNST patients with unresectable or metastatic tumors are dismal, and novel therapeutic strategies are required. Although patient-derived cancer cell lines are vital for basic research and preclinical studies, few MPNST cell lines are available from public cell banks. Therefore, the aim of this study was to establish cancer cell lines derived from MPNST patients.MethodsWe used tumor tissues from five patients with MPNSTs, including one derived from a rare bone tissue MPNST. The tumor tissues were obtained at the time of surgery and were immediately processed to establish cell lines. A patient-derived xenograft was also established when a sufficient amount of tumor tissue was available. The characterization of established cells was performed with respect to cell proliferation, spheroid formation, and invasion. The mutation status of actionable genes was monitored by NCC Oncopanel, by which the mutation of 114 genes was assessed by next-generation sequencing. The response to anti-cancer agents, including anti-cancer drugs approved for the treatment of other malignancies was investigated in the established cell lines.ResultsWe established five cell lines (NCC-MPNST1-C1, NCC-MPNST2-C1, NCC-MPNST3-C1, NCC-MPNST4-C1, and NCC-MPNST5-C1) from the original tumors, and also established patient-derived xenografts (PDXs) from which one cell line (NCC-MPNST3-X2-C1) was produced. The established MPNST cell lines proliferated continuously and formed spheroids while exhibiting distinct invasion abilities. The cell lines had typical mutations in the actionable genes, and the mutation profiles differed among the cell lines. The responsiveness to examined anti-cancer agents differed among cell lines; while the presence of an actionable gene mutation did not correspond with the response to the anticipated anti-cancer agents.ConclusionThe established cell lines exhibit various characteristics, including proliferation and invasion potential. In addition, they had different mutation profiles and response to the anti-cancer agents. These observations suggest that the established cell lines will be useful for future research on MPNSTs.

Decitabine: A Historical Review of the Development Process of an Epigenetic Drug

Decitabine (5-aza-2p-deoxycytidine) is a hypomethylation agent with a double-action mechanism, these are the reactivation of silenced genes; exhibiting differentiation at low doses and showing cytotoxicity at high doses. Decitabine was used as a classic anticancer drug in the original studies in the 1980s, 1500 to 2500 mg/m2 per cycle was the maximum clinically tolerated dose. The dosage was reassessed after a better understanding of epigenetics in cancer and the role of decitabine in epigenetic (hypomethylation) therapy was obtained, in about 1/20th of the previous doses (i.e., 'optimal biological' doses modulating hypomethylation). It has been found that decitabine (100 to 150 mg / m2 per cycle) can be used in patients with myelodysplastic syndromes (MDS) and other myeloid tumors, with manageable side effects. Combination therapies that amplify the epigenetic effect of decitabine will most likely improve the patient responses and allow it to be used in the treatment of other malignancies.

Outcomes of nivolumab (NIVO)-treated patients (pts) with advanced non-small cell lung cancer (aNSCLC) in United States community oncology practice.

119 Background: The phase 3 Checkmate 017 and 057 trials demonstrated improved survival of NIVO vs. chemotherapy in pts who progressed on or after platinum-based chemotherapy for aNSCLC, regardless of histology (squamous [SQ]/non-squamous [NSQ]) and PD-L1 expression. Real-world (RW) long-term effectiveness data with PD-1 inhibitors are limited. This study evaluated RW adoption of I-O and outcomes of NIVO-treated pts with aNSCLC in community practices, overall and by histology. Methods: This retrospective observational study of US Oncology Network electronic health records and supplemental chart abstraction followed a cohort of pts with aNSCLC receiving PD-1 inhibitors for ≥17 months, from initial FDA approval, 03/2015 through 10/2017. Pts in clinical trials or receiving treatment for other malignancies were excluded. Demographic and clinical features were characterized. Duration of therapy (DOT) and overall survival (OS) were assessed by the Kaplan-Meier method. Results: Of 217 included pts, 203 received NIVO; outcomes for 14 receiving pembrolizumab are not presented. NIVO was administered as first-line (1L) therapy in 15 pts, 2L+ therapy in 188 pts (n = 134 LOT2, n = 54 LOT3-4). For all 2L+ pts treated with a PD-1 inhibitor, median age was 70 years, 57% were male, 73% had NSQ histology, and 82% had ECOG performance status of 0-1. All pts with biomarker data were ALK negative and 5% were EGFR positive. Approximately 13% of pts had PD-L1 testing, of whom 6% were positive (expression > 1%). For 2L+, DOT (median months [mos], 95% CI) was 3.5 (3.0, 4.1) in the overall population, 3.3 (1.9, 4.2) with SQ, and 3.6 (2.3, 4.6) with NSQ histology. Of all 2L+ pts, 30.3% (95% CI 23.9%, 37.0%) remained on treatment at 6 mos. For 2L+, OS (median mos, 95% CI) was 8.7 (7.6, 11.0) overall, 7.0 (3.8, 9.1) with SQ, and 10.5 (8.4, 13.3) with NSQ histology; 1-year OS was 35%. Conclusions: RW DOT and OS for 2L+ NIVO treatment of aNSCLC were similar to outcomes reported in the phase 3 Checkmate 017 and 057 trials, with longer DOT and greater OS in patients with NSQ histology. Few RW pts had PD-L1 testing in this 2L+setting. Future analyses are needed to assess the uptake of PD-1 inhibitors for 1L treatment of aNSCLC.

Pharmacogenetics of asparaginase in acute lymphoblastic leukemia.

Asparaginase is a key component in leukemias and lymphomas treatment protocols and is suggested as a treatment for other malignancies in which an amino acid depletion strategy is indicated. Asparaginase intolerance is subject to inter-individual variability and can manifest as hypersensitivity reactions, pancreatitis, thrombosis, as well as metabolic abnormalities, and may affect treatment outcome. Pharmacogenetics aims at enhancing treatment efficacy and safety by better understanding the genetic basis of variability and its effect on the pharmacological responses. Many groups tried to tackle the pharmacogenetics of asparaginase but the potential implementation of such findings remains debatable. In this review, we highlight the most important findings reported in studies of the pharmacogenetics of asparaginase related complications and treatment outcome in acute lymphoblastic leukemia.

Phase II study of neoadjuvant checkpoint blockade in patients with surgically resectable undifferentiated pleomorphic sarcoma and dedifferentiated liposarcoma

BackgroundSoft tissue sarcomas are a heterogeneous and rare group of solid tumors of mesenchymal origin that can arise anywhere in the body. Although surgical resection is the mainstay of treatment for patients with localized disease, disease recurrence is common and 5-year overall survival is poor (~ 65%). Both radiation therapy and conventional chemotherapy are used to reduce local and distant recurrence. However, the utility of radiation therapy is often limited by disease location (in the case of retroperitoneal sarcomas, for instance) while systemic therapy with conventional lines of chemotherapy offer limited efficacy and are often poorly tolerated and associated with significant toxicity. Within the past decade, major advances have been made in the treatment of other malignancies including melanoma, renal cell carcinoma, and non-small cell lung carcinoma with the advent of immune-checkpoint inhibitors such as ipilimumab (anti-CTLA4), pembrolizumab (anti-PD1), and nivolumab (anti-PD1). The recently published SARC028 (NCT02301039), an open label, phase II, multicenter trial of pembrolizumab in patients with advanced bone and soft tissue sarcomas reported promising activity in select histologic subtypes of advanced STS, including undifferentiated pleomorphic sarcoma and dedifferentiated liposarcoma.MethodsThere is a clear need for novel and effective adjuncts in the treatment of STS. We hypothesize that immune checkpoint blockade will be effective in patients with surgically resectable primary or locally recurrent dedifferentiated liposarcoma and undifferentiated pleomorphic sarcoma when administered in the neoadjuvant setting. The primary aim of this phase II, single-center, open label, randomized non-comparative trial is to determine the pathologic response to neoadjuvant nivolumab monotherapy and combination nivolumab/ipilimumab in patients with resectable dedifferentiated liposarcoma of the retroperitoneum or undifferentiated pleomorphic sarcoma of the trunk or extremity treated with concurrent standard of care neoadjuvant radiation therapy.DiscussionThis study will help define the role of single agent anti-PD1 and combination anti-CTLA4 and anti-PD1 therapy in patients with surgically resectable dedifferentiated liposarcoma and undifferentiated pleomorphic sarcoma.Trial registrationClinicalTrials.govNCT03307616, registered October 12, 2017.

Palbociclib-induced autophagy and senescence in gastric cancer cells

Targeting cyclin D-CDK4/6 kinase complexes has recently been shown to increase the survival of breast cancer patients with estrogen receptor positive breast tumors. Based on these outcomes, CDK4/6 inhibitors are currently being tested, alone o in combination with other drugs, in the treatment of other malignancies characterized by hyper-activation of cyclin D-CDK4/6 complexes. Nonetheless, a better understanding of the cellular processes that are implemented in response to CDK4/6 inhibition is necessary to expand the therapeutic window and confront the development of drug resistance. Herein, we show that, similar to mammary cells, gastric cancer cells are sensitive to the CDK4/6 inhibitor Palbociclib. Inhibition of CDK4/6 in gastric cancer cells leads to the implementation of cellular senescence. However, whether or not this response is accompanied by induction of autophagy seems to depend on both the pRB and p53 status. In cells retaining expression of both tumor suppressive proteins (AGS gastric cancer cells), exposure to Palbociclib induces senescence and autophagy. However, the simultaneous blockade of CDK4/6 and autophagy in these cells exacerbates the senescence phenotype, an indication that autophagy in these experimental settings represents an adaptive mechanism that promotes cell survival rather than being an effector mechanism of senescence. Interestingly, knocking down p53 resulted in senescence reduction and autophagy blockade, the latter apparently involving a disruption of the degradation of autophagosome cargo.

Abstract 3166: Loss of PARP1 in human cancer cells confers resistance to PARP inhibition via activation of innate immune signaling

Abstract Purpose: PARP inhibitors (PARPi) are FDA-approved for the treatment of ovarian cancer and in clinical trials for the treatment of other malignancies. PARPi block the catalytic site of PARP1, a poly(ADP-ribose) polymerase that catalyzes the repair of DNA single-strand breaks (SSBs) and double-strand breaks (DSBs). Although cancer cells harboring defects in Homologous Recombination (HR) are particularly sensitive to PARPi, disease progression is eventually observed due to the emergence of resistant cells. To address the mechanisms leading to PARPi resistance and identify novel preventive strategies, we have generated and characterized multiple human cancer cell lines genetically engineered to acquire PARPi resistance via depletion of PARP1. Experimental Procedures: We used CRISPR/Cas9D10A (“double nickase”) to introduce DSBs within exon 2 of PARP1 in human cancer cell lines HCT116 and HEK293T. After allowing for repair via endogenous error-prone pathways, single cell-derived subclones were screened by immunoblotting with an antibody to PARP1. PARP1 “knock out” (KO) clones were further analyzed for proliferation, cell cycle distribution and sensitivity to DNA damaging agents, including ionizing radiation (IR) and the PARPi olaparib. Radiation response was assessed using proliferation and clonogenic assays, immunofluorescence (IF) for γ-H2AX and immunoblotting for ATM substrates phospho-KAP1 (Ser824) and phospho-CHK2 (Thr68). Finally, differential gene expression between PARP1-proficient and deficient HCT116 and HEK293T cells was analyzed by RNA-Seq. Findings: Although genetic depletion of PARP1 initially led to significant death of HCT116 and HEK293T mass cultures, surviving cells could be isolated to establish stable PARP1 KO clones. Relative to PARP1-proficient controls, HCT-116PARP1-/- and HEK293TPARP1-/- cells exhibited decreased proliferation and clonogenic capacity in vitro and decreased growth in vivo. In addition, loss of PARP1 led to radiosensitivity and persistent activation of cell cycle checkpoints, delayed kinetics of γ-H2AX foci resolution and persistent ATM signaling after IR. In contrast, PARP1 loss induced resistance to the PARPi olaparib in both lines. PARP1 reconstitution using either stable or transient approaches resulted in only a partial rescue of these phenotypes. RNA-Seq analyses revealed increased expression of innate immune signaling and inflammatory cascades upon PARP1 loss, including type I/III interferons and their inducible genes. Conclusions: PARP1 KO human cancer cells may represent a valuable preclinical model to investigate mechanisms underlying resistance to PARP inhibitors observed in the clinical setting. Loss of PARP1 triggers activation of “viral mimicry” in cancer cells, suggesting that drugs targeting this pathway may synergize with PARPi to kill cancer cells and prevent the emergence of resistance. Citation Format: Rajib Ghosh, Sanchita Roy, Sonia Franco. Loss of PARP1 in human cancer cells confers resistance to PARP inhibition via activation of innate immune signaling [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3166. doi:10.1158/1538-7445.AM2017-3166

Palbociclib induces activation of AMPK and inhibits hepatocellular carcinoma in a CDK4/6-independent manner.

Palbociclib, a CDK4/6 inhibitor, has recently been approved for hormone receptor‐positive breast cancer patients. The effects of palbociclib as a treatment for other malignancies, including hepatocellular carcinoma (HCC), are of great clinical interest and are under active investigation. Here, we report the effects and a novel mechanism of action of palbociclib in HCC. We found that palbociclib induced both autophagy and apoptosis in HCC cells through a mechanism involving 5′ AMP‐activated protein kinase (AMPK) activation and protein phosphatase 5 (PP5) inhibition. Blockade of AMPK signals or ectopic expression of PP5 counteracted the effect of palbociclib, confirming the involvement of the PP5/AMPK axis in palbociclib‐mediated HCC cell death. However, CDK4/6 inhibition by lentivirus‐mediated shRNA expression did not reproduce the effect of palbociclib‐treated cells, suggesting that the anti‐HCC effect of palbociclib is independent of CDK4/6. Moreover, two other CDK4/6 inhibitors (ribociclib and abemaciclib) had minimal effects on HCC cell viability and the PP5/AMPK axis. Palbociclib also demonstrated significant tumor‐suppressive activity in a HCC xenograft model, which was associated with upregulation of pAMPK and PP5 inhibition. Finally, we analyzed 153 HCC clinical samples and found that PP5 expression was highly tumor specific and was associated with poor clinical features. Taken together, we conclude that palbociclib exerted antitumor activity against HCC through the PP5/AMPK axis independent of CDK4/6. Our findings provide a novel mechanistic basis for palbociclib and reveal the therapeutic potential of targeting PP5/AMPK signaling with a PP5 inhibitor for the treatment of hepatocellular carcinoma.

IGH/MYC Translocation in Burkitt Lymphoma Is Associated with BRCA2 Deficiency and Synthetic Lethality By PARP1 Inhibitors

Burkitt lymphoma/leukemia (BL) is a highly aggressive mature B-cell neoplasm characterized by chromosomal rearrangements of the c-myc oncogene resulting in the overexpression of MYC transcription factor. The most common translocation is the t(8;14)(q24;q32) (85% of all cases), which involves MYC and IGH loci to generate IGH/MYC. Deregulation of MYC, a potent proto-oncogene and transcriptional regulator contributes to lymphomagenesis through alterations in cell cycle regulation, and cell differentiation, apoptosis, adhesion, and metabolism.BL treatment consists of high-intensity chemotherapy protocols that include cyclophosphamide, cytarabine (AraC) and doxorubicin. Current therapies have achieved a very favorable outcome resulting in complete remission in 75% to 90% of BL patients and a survival rate of 70% to 80%. However the current treatment for BL is suboptimal in elderly patients or patients with advanced-stage diseased, in the setting of HIV infections, as well as in the setting of relapsed disease. Therefore new therapeutic strategies are necessary to improve the outcomes in BL diseases in the poor prognosis patients.It has been reported that overexpression of MYC caused accumulation of potentially lethal DNA double-strand breaks (DSBs), which can modulate the response of tumor cells to genotoxic treatment. Therefore, we examined the consequences of DSBs accumulation in IGH/MYC-positive BL cells. Here we show that untreated and cytarabine (AraC)-treated IGH/MYC-positive BL cells accumulate high number of potentially lethal DNA double-strand breaks (DSBs) and display downregulation of BRCA2 tumor suppressor protein, which is a key element of homologous recombination - mediated DSB repair. BRCA2 deficiency in IGH/MYC-positive cells was associated with hypersensitivity to PARP1 inhibitors (olaparib, talazoparib) used alone or in combination with cytarabine in vitro. Moreover, talazoparib exerted a therapeutic effect in NGS mice bearing primary BL xenografts.In conclusion, we postulate that BRCA2 deficiency may predispose BL cells to synthetic lethality triggered by PARP1 inhibitor, such as recently FDA approved olaparib. Moreover, PARP1 inhibitor may be useful for the treatment of other malignancies associated with deregulation of MYC, including diffuse large B-cell lymphoma (DLBCL) and ALK-positive LBCL. DisclosuresWasik:Gilead Sciences: Equity Ownership; Seattle Genetics: Honoraria; Novartis: Research Funding; University of Pennsylvania: Patents & Royalties: NPM-ALK as an omncogene; University of Pennsylvania: Patents & Royalties: CAR T-cells; Gilead Sciences: Research Funding; Pharmacyclics: Research Funding.