Rb Protein Expression Research Articles

SNRPB2 promotes triple-negative breast cancer progression by controlling alternative splicing of MDM4 pre-mRNA.

Alternative splicing generates cancer-specific transcripts and is now recognized as a hallmark of cancer. However, the critical oncogenic spliceosome-related proteins involved in triple-negative breast cancer (TNBC) remain elusive. Here, we explored the expression pattern of spliceosome-related proteins in TNBC, non-TNBC, and normal breast tissues from The Cancer Genome Atlas breast cancer (TCGA-BRCA) cohort, revealing higher expression of nearly half of spliceosome-related proteins in TNBC than their counterparts. Among these TNBC-specific spliceosome-related proteins, the expression of SNRPB2 was associated with poor prognosis in patients with TNBC. In TNBC cells, the knockdown of SNRPB2 strongly suppressed cell proliferation and invasion and induced cell cycle arrest. Mechanistically, transcriptome data showed that SNRPB2 knockdown inactivated E2F1 signaling, which regulated the cell cycle. We further validated the downregulation of several cell cycle genes in SNRPB2 knockdown cells. Moreover, the analysis showed that SNRPB2 knockdown triggered the alteration of many alternative splicing events, most of which were skipping of exon. In TNBC cells, it was found that SNRPB2 knockdown led to the skipping of exon 6 in MDM4 pre-mRNA, generating MDM4-S transcript and downregulating MDM4 protein expression. More importantly, downregulation of MDM4 decreased retinoblastoma 1 (Rb1) protein expression, which is a target of MDM4 and a regulator of E2F1 signaling. In summary, the current study revealed an SNRPB2/MDM4/Rb axis in promoting the progression of TNBC, providing novel insights and novel targets for combating TNBC.

Identification of human papillomavirus and Rb/E2F pathway genomic alterations in mixed adeno-neuroendocrine carcinoma.

To investigate the molecular characteristics of Rb/E2F in mixed adeno-neuroendocrine carcinoma (MANEC). The clinicopathological features of MANEC were analyzed. The protein expressions of Rb, p16, and p53 were detected by the immunohistochemical method. The infection status of high-risk human papillomavirus (HR-HPV) was evaluated by in situ hybridization (ISH) and the gene chip method. Thirteen cases of MANEC were divided into four molecular patterns according to Rb protein expression and HPV status. Group 1: A total of eight of the 13 cases showed positive Rb protein expression and lack of HR-HPV expression (8/13, 62%). Rb protein expression with p16 protein deletion and p53 protein abnormal expression was unique to NEC. Group 2: three cases (3/13, 23%) with negative Rb protein expression and lack of HR-HPV expression. Group 3: There was one case (1/13, 8%) with positive expression of Rb protein accompanied by HR-HPV. Group 4: There was one case of Rb protein loss with an HR-HPV-positive status. HR-HPV and Rb/p16/p53 pathway can be associated in MANEC pathogenesis, which provides the research basis for personalized treatment of MANEC.

Concurrent RB1 Loss and BRCA Deficiency Predicts Enhanced Immunologic Response and Long-term Survival in Tubo-ovarian High-grade Serous Carcinoma.

The purpose of this study was to evaluate RB1 expression and survival across ovarian carcinoma histotypes and how co-occurrence of BRCA1 or BRCA2 (BRCA) alterations and RB1 loss influences survival in tubo-ovarian high-grade serous carcinoma (HGSC). RB1 protein expression was classified by immunohistochemistry in ovarian carcinomas of 7,436 patients from the Ovarian Tumor Tissue Analysis consortium. We examined RB1 expression and germline BRCA status in a subset of 1,134 HGSC, and related genotype to overall survival (OS), tumor-infiltrating CD8+ lymphocytes, and transcriptomic subtypes. Using CRISPR-Cas9, we deleted RB1 in HGSC cells with and without BRCA1 alterations to model co-loss with treatment response. We performed whole-genome and transcriptome data analyses on 126 patients with primary HGSC to characterize tumors with concurrent BRCA deficiency and RB1 loss. RB1 loss was associated with longer OS in HGSC but with poorer prognosis in endometrioid ovarian carcinoma. Patients with HGSC harboring both RB1 loss and pathogenic germline BRCA variants had superior OS compared with patients with either alteration alone, and their median OS was three times longer than those without pathogenic BRCA variants and retained RB1 expression (9.3 vs. 3.1 years). Enhanced sensitivity to cisplatin and paclitaxel was seen in BRCA1-altered cells with RB1 knockout. Combined RB1 loss and BRCA deficiency correlated with transcriptional markers of enhanced IFN response, cell-cycle deregulation, and reduced epithelial-mesenchymal transition. CD8+ lymphocytes were most prevalent in BRCA-deficient HGSC with co-loss of RB1. Co-occurrence of RB1 loss and BRCA deficiency was associated with exceptionally long survival in patients with HGSC, potentially due to better treatment response and immune stimulation.

RB1 Genetic Alterations in Estrogen Receptor–Positive Breast Carcinomas: Correlation With Neuroendocrine Differentiation

Genetic alterations in the retinoblastoma susceptibility gene (RB1) are present in up to 40% of triple-negative breast cancers (BCs) and frequent in tumors with neuroendocrine differentiation, including small cell neuroendocrine carcinoma. Data on RB1 genetic alterations in estrogen receptor (ER)–positive BCs are scarce. In this study, we sought to define the morphologic, immunohistochemical, and genetic features of ER-positive BCs harboring somatic alterations in RB1, with emphasis on neuroendocrine differentiation. ER-positive BCs with pathogenic RB1 genetic alterations were identified in <1% of cases (N = 55) from a cohort of 6026 BCs previously subjected to targeted next-generation sequencing, including 23 primary BCs (pBCs) and 32 recurrent/metastatic BCs (mBCs). In cases where loss of heterozygosity of the wild-type RB1 allele could be assessed (93%, 51/55), most pBCs (82%, 18/22) and mBCs (90%, 26/29) exhibited biallelic RB1 inactivation, primarily through loss-of-function mutation and loss of heterozygosity (98%, 43/44). Upon histologic review, a subset of RB1-altered tumors exhibited neuroendocrine morphology (13%, 7/55), which correlated with expression of neuroendocrine markers (39%, 9/23) in both pBCs (27%, 3/11) and mBCs (50%, 6/12). Loss of Rb protein expression was observed in BCs with biallelic RB1 loss only, with similar frequency in pBCs (82%, 9/11) and mBCs (75%, 9/12). All cases with neuroendocrine marker expression (n = 9) and/or neuroendocrine morphology (n = 7) harbored biallelic genetic inactivation of RB1 and exhibited Rb loss of expression. TP53 (53%, 29/55) and PIK3CA (45%, 25/55) were the most frequently comutated genes across the cohort. Overall, these findings suggest that ER-positive BCs with biallelic RB1 genetic alterations frequently exhibit Rb protein loss, which correlates with neuroendocrine differentiation in select BCs. This study provides insights into the molecular and phenotypic heterogeneity of BCs with RB1 genetic inactivation, underscoring the need for further research into the potential clinical implications associated with these tumors.

Abstract 1992: A novel RB1 E3 ligase TRIM37 contributes to palbociclib resistance in breast cancer

Abstract The tripartite motif-containing 37 (TRIM37) is a RING finger E3 ubiquitin ligase and is a poor prognostic factor in breast cancer patients. The gene is located in chromosome 17q23, a region amplified in up to 40% of breast cancers. We observed that activation of androgen receptor (AR) could induce resistance to the CDK4/6 inhibitor Palbociclib, the mechanism yet to be clarified. ChIP-sequencing data suggested that AR binds to the TRIM37 promoter, with AR activation resulting in TRIM37 expression. We hypothesized that TRIM37 might be involved in Palbociclib resistance. Using an ER+ve cell line MCF7 and a TNBC cell line MDA-MB 453, we found that overexpression of TRIM37 could induce Palbociclib resistance. TRIM37 overexpression resulted in RB1 protein downregulation, which is the primary downstream target of CDK4/6, while TRIM37 knockdown enhanced RB1 protein expression. Ubiquitination assay demonstrated TRIM37 overexpression increased the level of RB1 protein ubiquitination. The co-immunoprecipitation (Co-IP) assay confirmed that TRIM37 protein could interact with the RB1 protein. These results suggest that TRIM37 could be the E3 ligase that regulates RB1 degradation. Various deletion mutants of TRIM37 were cloned for Co-IP experiments between these mutants and RB1. Results show that the MATH and c-terminal domains of TRIM37 was the essential region for the interaction. Overexpression of the mutant with the TRIM37 MATH and c-terminal domains (TRIM37-MATH/C) could enhance RB1 protein level. This might be due to competition of TRIM37-MATH/C with wild-type TRIM37 for RB1 binding. Our findings suggest TRIM37 is a novel RB1 E3 ligase, and it binds to the RB1 protein via the MATH and C-terminal domains to regulate protein degradation. Our study also suggests that high expression of TRIM37 mediated by AR activation could deplete RB1, which is the target of Palbociclib, eventually leading to resistance. These findings are supportive of the contribution of AR activation to Palbociclib resistance. Citation Format: Chanping You, Ho Tsoi, Pui Sum Man, Larry Ka Yue Chow, Wei Dai, Ui Soon Khoo. A novel RB1 E3 ligase TRIM37 contributes to palbociclib resistance in breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1992.

Anti-Cancer Effects of CDK4/6 Inhibitor LEE011 and Chemotherapy Drugs on Lymphocytic Leukemia L1210 Cells.

Chronic lymphocytic leukemia is a slowly-progressing disease in which symptoms often do not manifest until years after disease onset. In advanced stages, infection and bleeding are common. Past studies have shown that the interaction between CDK4/6 inhibitors and chemotherapy drugs can enhance the anti-tumor efficacy of drugs and limit toxicity. Therefore, in this study, the treatment effects of combining the CDK4/6 inhibitor LEE011 with chemotherapy drugs bendamustine or hydroxyurea were investigated in vitro. The mouse lymphocytic leukemia cell line L1210 was treated with LEE011 combined with hydroxyurea or bendamustine. Western blot and flow cytometry were performed to elucidate the mechanisms behind tumor suppression. LEE011 combined with hydroxyurea or bendamustine significantly inhibited proliferation of L1210 cell lines in a concentration- and time-dependent manner as well as increased the arrest of cells in G1 and S phases. The combination of LEE011 with hydroxyurea also reduced the phosphorylation of Rb while increased the expression of total Rb protein. Furthermore, reduced expression of GPX4, which is a key protein in ferroptosis, indicates that the tumor suppression effects of this drug combination could involve ferroptosis. CDK4/6 inhibitor LEE011 treatment alone may not be a suitable treatment option for lymphocytic leukemia; however, our findings in vitro support the combination of LEE011 with chemotherapy drugs to enhance anti-tumor activity in lymphocytic leukemia.

Chondrolipoma of the Breast: A Myofibroblastoma Variant or a Distinct Lesion?

The entity commonly referred to as chondrolipoma is a rare and enigmatic breast lesion with unclear histogenesis and a complete lack of molecular characterization. It is uncertain whether it represents a hamartoma, choristoma, or a distinct neoplasm, including possibly a variant of mammary-type myofibroblastoma. We report two additional chondrolipomatous lesions of the breast. The lesions had varying histologic and immunohistochemical features similar to myofibroblastoma, including the loss of retinoblastoma (Rb) protein expression in one lesion. Molecular analysis by chromosomal microarray analysis performed on a second lesion did not demonstrate a loss of 13q14 or 16q typical of myofibroblastoma. Our findings further support the concept that at least a subset of breast lesions that historically have been classified as chondrolipoma are related to myofibroblastoma. However, the lack of myofibroblastoma-specific molecular alterations in one lesion suggests chondrolipomas may also have varying origins.

Abstract B058: Deconvoluting the intra-tumour heterogeneity and subclonal evolution of CDK4/6 inhibitor resistance in ER+ breast cancer

Abstract Subclonal heterogeneity and evolution are characteristics of breast cancer (BC), that play a key role in tumour development, progression, and resistance to current therapies. Preliminary single-cell sequencing studies suggest that subclonal heterogeneity drives therapy response in aggressive BC. Here, we sought to identify whether pre-existing transcriptomically defined cell subpopulations underpin resistance to CDK4/6 inhibitors (CDK4/6i) in ER+ BC, and to identify the distinct or shared resistance mechanisms between different CDK4/6i currently used in the clinic. ER+ BC cell lines, MCF7 and T47D, were infected with a lentiviral barcode library and were long-term exposed to DMSO or CDK4/6i (Abemaciclib or Palbociclib) until drug resistance was achieved. CDK4/6i resistant or DMSO cell lines were then subjected to DNA sequencing for the detection of barcodes coupled with single-cell transcriptomic and barcode sequencing, whole exome sequencing and G1/S cell cycle checkpoint analysis at a protein level. Single-cell lineage tracing identified that resistance to both CDK4/6i in MCF7 cells was stochastic, while in T47D cells, resistance to both CDK4/6i was conserved across all biological replicates. In all cell models, abemaciclib exerted a stronger selective pressure than palbociclib. Detection of barcodes from dead cells highlighted differential selective pressures of the drugs during resistance generation and upon resistance emergence. Single-cell transcriptomic sequencing identified shared and differential mechanisms of resistance between cell lines and specific CDK4/6i, suggestive of different subclonal, non-genetic mechanisms driving resistance. Some of these subclones were pre-defined (i.e. shared transcriptomic features with parental cells), whereas other resistant subclones were demarked by acquisition of pathway up-regulation. For instance, RB1 expression was abolished in the entire palbociclib-resistant T47D population, with copy number loss, indicating RB1 as a genetic driver of resistance. No evidence of RB1 loss was observed in MCF7 palbociclib-resistant clonal population, however a subclonal cluster was identified with loss of RB1 expression. Interestingly, abemaciclib-resistant MCF7 cells had lost RB1 protein expression, suggesting differential non-genetic mechanisms of resistance to CDK4/6i in MCF7 cells. Through single-cell lineage tracing, we have identified that resistance to CDK4/6i can be stochastic or conserved according to the cell model. Additionally, single-cell transcriptomic sequencing identified that in some cell models, cells that have the ability to become resistant are pre-existing, suggesting transcriptomic and epigenomic mechanisms of resistance, where cells exhibit drug-tolerant or drug-induced persistent properties. Citation Format: Ioanna Mavrommati, Fatemeh Ahmadi Moughari, Shefali Thakur, Yu Zhang, Lesley-Ann Martin, Syed Haider, Rachael Natrajan. Deconvoluting the intra-tumour heterogeneity and subclonal evolution of CDK4/6 inhibitor resistance in ER+ breast cancer [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Breast Cancer Research; 2023 Oct 19-22; San Diego, California. Philadelphia (PA): AACR; Cancer Res 2024;84(3 Suppl_1):Abstract nr B058.

Sirtuin Inhibitor Cambinol Induces Cell Differentiation and Differently Interferes with SIRT1 and 2 at the Substrate Binding Site.

Epigenetic mechanisms finely regulate gene expression and represent potential therapeutic targets. Cambinol is a synthetic heterocyclic compound that inhibits class III histone deacetylases known as sirtuins (SIRTs). The acetylating action that results could be crucial in modulating cellular functions via epigenetic regulations. The main aim of this research was to investigate the effects of cambinol, and its underlying mechanisms, on cell differentiation by combining wet experiments with bioinformatics analyses and molecular docking simulations. Our in vitro study evidenced the ability of cambinol to induce the differentiation in MCF-7, NB4, and 3T3-L1 cell lines. Interestingly, focusing on the latter that accumulated cytoplasmic lipid droplets, the first promising results related to the action mechanisms of cambinol have shown the induction of cell cycle-related proteins (such as p16 and p27) and modulation of the expression of Rb protein and nuclear receptors related to cell differentiation. Moreover, we explored the inhibitory mechanism of cambinol on human SIRT1 and 2 performing in silico molecular simulations by protein-ligand docking. Cambinol, unlike from other sirtuin inhibitors, is able to better interact with the substrate binding site of SIRT1 than with the inhibition site. Additionally, for SIRT2, cambinol partially interacts with the substrate binding site, although the inhibition site is preferred. Overall, our findings suggest that cambinol might contribute to the development of an alternative to the existing epigenetic therapies that modulate SIRTs.

Inhibition of ferroptosis ameliorates hypertensive nephropathy through p53/Nrf2/p21 pathway by Taohongsiwu decoction: Based on network pharmacology and experimental validation

Ethnopharmacological relevanceHypertensive nephropathy (HN) is a complication of hypertension. Taohongsiwu decoction (THSWD) is used clinically but its application in the prevention and treatment of HN remains unelucidated. Aim of studyThis study aims to explore the potential targets and molecular mechanisms of THSWD in the treatment of HN. Materials and methodsA network pharmacology approach was used to predict the components and targets of THSWD for treating HN. Animal experiments were performed to verify the network pharmacology findings. Results205 targets were identified and regarded as potential targets of THSWD in HN treatment. Subsequently, we screened 17 hub genes and identified TP53 as the most critical one. KEGG enrichment analysis showed that p53 signaling pathway might play a significant role. In vivo experiments indicated that high-salt diets can lead to high blood pressure, kidney injury, inflammation, and fibrosis. Furthermore, the altered levels of biomarkers (Iron, malondialdehyde, catalase, ferritin, transferrin, Superoxide dismutase and Glutathione Peroxidase 4) provided evidence of ferroptosis. We found that the ferroptosis inhibitor ferrostatin-1 (Fer-1) and THSWD could significantly alleviate HN by suppressing ferroptosis. THSWD and Fer-1 treatment downregulated the protein and mRNA expression of p53, p21, RB, and CTNNB1, which were upregulated by high salt. Meanwhile, THSWD and Fer-1 reversed the downregulation of Nrf2 caused by high-salt diet. ConclusionsOur results suggested that THSWD attenuate HN induced by a high-salt diet through inhibiting ferroptosis via the p53/Nrf2/p21 pathway.

Retinoblastoma Expression and Targeting by CDK4/6 Inhibitors in Small Cell Lung Cancer.

The canonical model of "small cell lung cancer" (SCLC) depicts tumors arising from dual inactivation of TP53 and RB1. However, many genomic studies have persistently identified tumors with no RB1 mutations. Here, we examined RB1 protein expression and function in SCLC. RB1 expression was examined by IHC analysis of 62 human SCLC tumors. These studies showed that ∼14% of SCLC tumors expressed abundant RB1 protein, which is associated with neuroendocrine gene expression and is enriched in YAP1 expression, but no other lineage proteins that stratify SCLC. SCLC cells and xenograft tumors with RB1 protein expression were sensitive to growth inhibition by the CDK4/6 inhibitor palbociclib, and this inhibition was shown to be dependent on RB1 expression by CRISPR knockout. Furthermore, a patient with biopsy-validated wild-type RB1 SCLC who received the CDK4/6 inhibitor abemaciclib demonstrated a dramatic decrease in mutant TP53 ctDNA allelic fraction from 62.1% to 0.4% and decreased tumor mass on CT scans. Importantly, IHC of the diagnostic biopsy specimen showed RB1 positivity. Finally, we identified a transcriptomics-based RB1 loss-of-function signature that discriminates between SCLC cells with or without RB1 protein expression and validated it in the patient who was responsive to abemaciclib, suggesting its potential use to predict CDK4/6 inhibitor response in patients with SCLC. Our study demonstrates that RB1 protein is an actionable target in a subgroup of SCLC, a cancer that exhibits no currently targetable mutations.

Effects of p16/pRb and JNK signaling pathways in hydroquinone-induced malignant transformation of TK6 cells

Objective: To investigate the cell cycle and apoptosis in hydroquinone (HQ) -induced malignant transformation of TK6 cells and its related regulatory mechanisms. Methods: TK6 cells were exposed to 20 μmol/L HQ, 24 h/time, once a week, for 19 weeks as experimental group and TK6 cells treated with phosphate buffer (PBS) for 19 weeks was used as control group from March 2014. In regulatory mechanism research, the cells were divided into four groups: control group, experimental group, control inhibitor group and experimental inhibitor group (inhibitor groups were added 10 μmol/L P600125) . Cell cycle and apoptosis were detected by flow cytometry. The protein expression of cell cycle-related proteins and JNK signaling pathway proteins were detected by Western blot. Results: Flow cytometry showed that compared with control group, the ratio of cells in the G0/G1 phase of the experimental group was significantly decreased (P=0.001) , and the ratio of cells in the S phase was significantly increased (P=0.002) . Western blotting demonstrated that the protein expressions of p-Rb (Ser780) , E2F1, Cyclin D1, p-p16 (Ser152) , JNK1, p-JNK1 (Thr183/Tyr185) , c-jun, p-c-jun (Ser63) (P=0.015, 0.021, 0.001, 0.001, 0.005, 0.001, 0.039, 0.003) were up-regulated, while the protein expressions of Rb (P=0.048) and p16 (P=0.002) were significantly down-regulated. After exposed to SP600125, compared with experimental group, there were no significant changes in cell cycle distribution (P=0.946) and apoptosis rate (P=0.923) in experimental inhibitor group. The expression of c-jun (P=0.040) protein was down-regulated, while the expression of Rb (P=0.027) protein was up-regulated in experimental inhibitor group. Conclusion: In HQ-induced TK6 cells malignant transformation, the cell cycle is arrested in the S phase, and the p16/pRb signaling pathway is inhibited, while the JNK signaling pathway is activated. However, the activated JNK signaling pathway may not be involved in the regulation of cell cycle.

Investigation of Curcumin-Loaded OA400 Nanoparticle's Effect on the Expression of E6 and E7 Human Papilloma-Virus Oncogenes and P53 and Rb Factors in HeLa Cell Line.

Curcumin, a compound derived from the root of the Curcuma longa, has been confirmed as an anticancer, chemoprotective, and gene/protein regulatory agent. Nanoformulation of curcumin has been developed to increase its targeting efficiency, solubility, controlled release, and physical and chemical stability. This study investigated the effect of new nano-type curcumin, oleic acid-derived dendrosome (OA400 nanoparticles), on the expression of E6 and E7 human papillomavirus oncogenes and P53 and Rb factors in the HeLa cell line. After preparing nano-curcumin by mixing OA400 nano-carrier and curcumin, its effect was considered on the human cervical cancer cell line (HeLa cell line RRID: CVCL_003) and normal fibroblast cells. MTT assay and flow cytometry were used to evaluate cell viability and apoptosis. Furthermore, real-time RT-PCR and western blot analyses assessed RNA and protein expression of E6, E7, P53, and Rb. Statistical analyses were performed by GraphPad Prism 7 software. The nanoformulation of curcumin could reduce the expression of E6 and E7 oncogenes and increase P53 and Rb tumor suppressors in HeLa cancerous cells at 15 μM concentration; however, it had no significant effect on the viability of normal fibroblast cells. On the other hand, curcumin altered the expression of these genes at a 50-μM concentration. Gene and protein expression analysis indicated the up-regulation of P53 and Rb factors and the down-regulation of E6 and E7 under the influence of nano-curcumin treatment more than curcumin. These data indicate the potential of curcumin-loaded OA400 nanoparticles to be considered as a treatment option in cervical cancer investigations.

Interruption of aberrant chromatin looping is required for regenerating RB1 function and suppressing tumorigenesis

RB transcriptional corepressor 1 (RB1) is a critical regulatory gene in physiological and pathological processes. Genetic mutation is considered to be the main cause of RB1 inactivation. However, accumulating evidence has shown that not all RB1 dysfunction is triggered by gene mutations, and the additional mechanism underlying RB1 dysfunction remains unclear. Here, we firstly reveal that a CCCTC binding factor (CTCF) mediated intrachromosomal looping served as a regulatory inducer to inactivate RB1. Once the core genomic fragment was deleted by Clustered Regularly Interspaced Short Palindromic Repeats/Cas9 (CRISPR/Cas9), this intrachromosomal looping was disrupted. After the open of chromatin, Enhancer of Zeste Homolog 2 (EZH2) was released and decreased the level of Tri-Methyl-Histone H3 Lys27 (H3K27me3) at the RB1 promoter, which substantially restored the expression of RB protein (pRB) and inhibited tumorigenesis. In addition, targeted correction of abnormal RB1 looping using the small-molecule compound GSK503 efficiently restored RB1 transcription and suppressed tumorigenesis. Our study reveals an alternative transcriptional mechanism underlying RB1 dysfunction independent of gene mutation, and advancing the discovery of potential therapeutic chemicals based on aberrant chromatin looping.

Combined TRIP13 and Aurora Kinase Inhibition Induces Apoptosis in Human Papillomavirus-Driven Cancers.

Human papillomavirus (HPV) causes >5% of cancers, but no therapies uniquely target HPV-driven cancers. We tested the cytotoxic effect of 864 drugs in 16 HPV-positive and 17 HPV-negative human squamous cancer cell lines. We confirmed apoptosis in vitro and in vivo using patient-derived xenografts. Mitotic pathway components were manipulated with drugs, knockdown, and overexpression. Aurora kinase inhibitors were more effective in vitro and in vivo in HPV-positive than in HPV-negative models. We hypothesized that the mechanism of sensitivity involves retinoblastoma (Rb) expression because the viral oncoprotein E7 leads to Rb protein degradation, and basal Rb protein expression correlates with Aurora inhibition-induced apoptosis. Manipulating Rb directly, or by inducing E7 expression, altered cells' sensitivity to Aurora kinase inhibitors. Rb affects expression of the mitotic checkpoint genes MAD2L1 and BUB1B, which we found to be highly expressed in HPV-positive patient tumors. Knockdown of MAD2L1 or BUB1B reduced Aurora kinase inhibition-induced apoptosis, whereas depletion of the MAD2L1 regulator TRIP13 enhanced it. TRIP13 is a potentially druggable AAA-ATPase. Combining Aurora kinase inhibition with TRIP13 depletion led to extensive apoptosis in HPV-positive cancer cells but not in HPV-negative cancer cells. Our data support a model in which HPV-positive cancer cells maintain a balance of MAD2L1 and TRIP13 to allow mitotic exit and survival in the absence of Rb. Because it does not affect cells with intact Rb function, this novel combination may have a wide therapeutic window, enabling the effective treatment of Rb-deficient cancers.

Abstract 6308: Antitumor effects of RBPJ Inhibitor-1 on osteosarcoma cells

Abstract Osteosarcoma (OS) is the most common primary malignancy of the bone in adolescents and children with limited treatment options. Drug resistance to current therapy together with severe side effects urgently calls for alternative treatment strategies targeting critical cancer signaling pathways. Recently, our and other studies suggest that hyperactivation of Notch signaling contributes to the pathogenesis of human and murine OS, and its inhibition may be a therapeutic approach for the treatment of OS. Notch pathophysiological activity involves activated Notch (i.e. NICD, the notch intracellular domain) forming a nuclear complex with DNA-binding factors and coactivators such as recombination signal binding protein for immunoglobulin kappa J region (RBPJ). This evolutionary conserved mechanism is involved in the maintenance and survival of cancer stem cells, which can govern various cell activities like metastasis and chemoresistance. This study aims to examine the in vitro effects of targeting the NICD-RBPJ interaction using a small molecular inhibitor of the RBPJ (RIN1) on osteosarcoma cell lines. We found that treatment of 10 µM RIN1 on SJSA-1 (ATCC, CRL-2098), a human osteosarcoma cell line with a high Notch activity, can significantly decrease cell proliferation at 48 and 72 hours (h). We also found that at 10 µM of RIN1 affects SJSA-1 migration using a Boyden chamber-based cell system at 24 h, a time point where we find minimal contribution from an effect on cell proliferation. Treatment with RIN1 can block SJSA-1 clonogenicity, but we showed that it has limited ability to block SJSA-1 cell invasion. Treatment with RIN1 does not initiate or enhance the osteoblast-like differentiation of SJSA-1. Notch target genes HEY1 and CyclinD1 was significantly modulated in SJSA-1 cells upon treatment in a Notch-independent manner. Interestingly, treatment with RIN1 on SJSA-1 decreases SOX2 protein expression, a well-known cancer stem cell marker, and upregulates tumor suppressor RB1 protein expression. Ongoing studies include additional cellular function assays and RNA-seq transcriptomic analysis of RIN1’s effect on two Notch-dependent cancer cell lines including MB 157 (ATCC, CRL-7721) and T29 in its activating context. In summary, RIN1 has been shown to have a significant effect on the different cell behaviors of human osteosarcoma, which may eventually facilitate with the treatment of patients that have metastatic disease. Citation Format: Dakota Callahan, Leetoria Hinojosa, Haydee M. Torres, Jianning Tao. Antitumor effects of RBPJ Inhibitor-1 on osteosarcoma 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 6308.

Genomic evidence suggests that cutaneous neuroendocrine carcinomas can arise from squamous dysplastic precursors

Merkel cell carcinoma (MCC) is an aggressive cutaneous neuroendocrine carcinoma without a known dysplastic precursor. In some cases, MCC is associated with SCCIS in the overlying epidermis; however, the MCC and SCCIS populations display strikingly different morphologies, and thus far a relationship between these components has not been demonstrated. To better understand the relationship between these distinct tumor cell populations, we evaluated 7 pairs of MCC-SCCIS for overlapping genomic alterations by cancer profiling panel. A subset was further characterized by transcriptional profiling and immunohistochemistry. In 6 of 7 MCC-SCCIS pairs there was highly significant mutational overlap including shared TP53 and/or RB1 mutations. In some cases, oncogenic events previously implicated in MCC (MYCL gain, MDM4 gain, HRAS mutation) were detected in both components. Although FBXW7 mutations were enriched in MCC, no gene mutation was unique to the MCC component across all cases. Transcriptome analysis identified 2736 differentially expressed genes between MCC and SCCIS. Genes upregulated in the MCC component included Polycomb repressive complex targets; downregulated transcripts included epidermal markers, and immune genes such as HLA-A. Immunohistochemical studies revealed increased expression of SOX2 in the MCC component, with diminished H3K27Me3, Rb, and HLA-A expression. In summary, MCC-SCCIS pairs demonstrate clonal relatedness. The shift to neuroendocrine phenotype is associated with loss of Rb protein expression, decrease in global H3K27Me3, and increased expression of Merkel cell genes such as SOX2. Our findings suggest an epidermal origin of MCC in this setting, and to our knowledge provide the first molecular evidence that intraepithelial squamous dysplasia may represent a direct precursor for small cell carcinoma.

A proteogenomic portrait of lung squamous cell carcinoma

Lung squamous cell carcinoma (LSCC) remains a leading cause of cancer death with few therapeutic options. We characterized the proteogenomic landscape of LSCC, providing a deeper exposition of LSCC biology with potential therapeutic implications. We identify NSD3 as an alternative driver in FGFR1-amplified tumors and low-p63 tumors overexpressing the therapeutic target survivin. SOX2 is considered undruggable, but our analyses provide rationale for exploring chromatin modifiers such as LSD1 and EZH2 to target SOX2-overexpressing tumors. Our data support complex regulation of metabolic pathways by crosstalk between post-translational modifications including ubiquitylation. Numerous immune-related proteogenomic observations suggest directions for further investigation. Proteogenomic dissection of CDKN2A mutations argue for more nuanced assessment of RB1 protein expression and phosphorylation before declaring CDK4/6 inhibition unsuccessful. Finally, triangulation between LSCC, LUAD, and HNSCC identified both unique and common therapeutic vulnerabilities. These observations and proteogenomics data resources may guide research into the biology and treatment of LSCC.

The combination of ADSCs and 10% PRP increases Rb protein expression on senescent human dermal fibroblasts

Background: The senescence process in human dermal fibroblasts (HDFs) is caused by cell cycle withdrawal processes, one of which is the result of the retinoblastoma (Rb) protein being in a hypo-phosphorylated state. Since adipose-derived stem cells (ADSCs) have a paracrine effect, ADSCs were utilized to improve the senescence process of HDFs. The use of non-autologous cell culture media to grow ADSCs can be legally problematic; therefore, platelet-rich plasma (PRP) can be considered as an alternative medium. PRP contains various growth factors that can be used to process the reversal of senescent HDFs. The combination of ADSCs and PRP is expected to increase the expression of Rb protein in HDFs that have undergone the senescence process. Methods: This study was performed in vitro with a randomized sample, and non-blinded pre-and post-test control group. The primary culture of senescent HDFs was transfected with a combination of ADSCs and 10% PRP. The effect on migration was observed through the scratch test, while the effect of PRP on reversal senescence was observed through Sa-β-gal analysis and the expression of protein Rb with ELISA. Results: The senescent HDFs that received a combined transfection of ADSCs and 10% PRP proliferated rapidly in the scratch test. Based on the Sa-β-gal assay, they showed fewer senescent HDFs cells. The combination of ADSCs and 10% PRP elevated the expression of Rb protein significantly (P &lt; 0.001). Conclusions: The combination of ADSCs and 10% PRP was shown to have a reversal effect on the senescence process of HDFs in vitro.

Exosomes of Adipose-derived Stem Cells Conditioned Media Promotes Retinoblastoma and Forkhead-Box M1 Protein Expression

BACKGROUND: In the senescence process, the retinoblastoma (Rb) protein binds to E2F in hypophosphorylated conditions, preventing the cell to enter the S-phase in the cell cycle. Human Forkhead Box M1 (FOXM1) protein, key regulator G1/S and G2/M phases, decreases in the senescence process. Many studies have been carried out to reverse this system, one of which used exosomes of adipose-derived stem c ells conditioned media (ADSC-CM). These exosomes contain a variety of specific proteins which have pro-proliferation properties, however, little is known on the role of these exosomes toward the change of phosphorylated Rb and FOXM1. AIM: This study aims to find out the involvement of exosomes of ADSC-CM on these two proteins on senescence human dermal fibroblasts (HDFs). METHODS: In vitro experiment was undergone randomization sample and non-blinded pre-/post-test control group. The primary culture of senescent HDFs was transfected with exosomes of ADSC-CM; then, its effect on migration and senescence reversal was observed through analyzing Sa-β-gal, Rb, and FOXM1 protein expression. RESULTS: The expression of Sa-β-gal was higher in the control group. Our result demonstrated the exosome of ADSC-CM significantly induced the expression of Rb and FOXM1 protein in senescent HDFs (p &lt; 0.05). CONCLUSION: It proved that exosomes of ADSC-CM could shift the senescent fibroblast into metabolically active cells.