Abstract 2558: Determining the expression of RNA binding protein Rbm3 in tumor cells and immune cells in the tumor microenvironment in prostate cancer

Prostate cancer is the most common cancer among men. Currently, targeting the AR pathway, chemotherapy or immune-based therapies are major options but only provide a modest improvement in overall survival. RNA binding proteins have been shown to regulate AR expression in the progression of PCa. We and others have demonstrated that RNA binding protein RBM3 is upregulated in various solid tumors including PCa. We have also shown that RBM3 binds to 3’UTR of mRNAs of tumor-promoting factors and increases their mRNA stability and translation. However, the role of RBM3 in PCa is not well evaluated. We first analyzed the expression levels of RBM3 in the TCGA database. There was a significant increase in RBM3 expression even in cancers with a Gleason score of 6 upto Gleason 10 cancers. To confirm this we performed RT-PCR analyses of a prostate cancer cDNA panel. There was a significant increase in RBM3 expression in the PCa tissues compared to normal control. We used LNCaP and its derivative cell line C4-2B which show features of progressed disease such as metastatic capability and hormone independence. RT-PCR and western blot analyses demonstrated significantly higher RBM3 levels in C4-2B cells as compared to LNCaP cells suggesting a role for RBM3 in tumor progression. The tumor microenvironment also plays a very important role in prognosis of PCa. Specifically, tumor-associated macrophages (TAMs) have been shown to increase metastatic potential and increase tumor angiogenesis. To determine the levels of RBM3 expression and its effects on macrophage infiltration, we mined the TCGA database using TIMER2.0 software. There was a positive correlation of RBM3 expression with infiltration of both M1 and M2 macrophages. To further study the effect of interactions between PCa cells and TAMs, we used immortalized THP1 monocytes, which can be activated to M1 and M2 macrophages. We observed that just converting the THP1 cells to M1 or M2 macrophages increased RBM3 expression in both cell types. Also, when M1 and M2 macrophages were treated with conditioned media from LNCaP or C4-2B cells, there was an induction in the expression of RBM3. Similarly, when conditioned media from M0, M1, M2 activated THP1 cells were applied to LNCaP and C4-2B cells, there was an increase in RBM3 expression in the PCa cells. This suggests a positive cross-talk between the macrophages and PCa cells. We evaluated the cytokine profile in the conditioned media from M1 and M2 macrophages and determined that while M1 macrophages had increased levels of CXCL10, M2 macrophages showed higher levels of IL4 and IL10. Moreover, PCa cells have higher levels of CXCR3, the receptor for CXCL10. Together, these data suggest that crosstalk between TAMs and cancer cells in the PCA microenvironment plays a significant role in increasing RBM3 expression, which in turn enhances global translation of disease progression related genes.

Citation Format: Afreen Asif Ali Sayed, David Standing, Prasad Dandawate, Shahid Umar, Roy Jensen, Rahul Parikh, John Taylor, Shrikant Anant. Determining the expression of RNA binding protein Rbm3 in tumor cells and immune cells in the tumor microenvironment in prostate 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 2558.

Diphenylbutylpiperidine Antipsychotic Drugs Inhibit Prolactin Receptor Signaling to Reduce Growth of Pancreatic Ductal Adenocarcinoma in Mice

BACKGROUND & AIMS

Prolactin (PRL) signaling is up-regulated in hormone-responsive cancers. The PRL receptor (PRLR) is a class I cytokine receptor that signals via the Janus kinase (JAK)-signal transducer and activator of transcription and mitogen-activated protein kinase pathways to regulate cell proliferation, migration, stem cell features, and apoptosis. Patients with pancreatic ductal adenocarcinoma (PDAC) have high plasma levels of PRL. We investigated whether PRLR signaling contributes to the growth of pancreatic tumors in mice.

METHODS

We used immunohistochemical analyses to compare levels of PRL and PRLR in multitumor tissue microarrays. We used structure-based virtual screening and fragment-based drug discovery to identify compounds likely to bind PRLR and interfere with its signaling. Human pancreatic cell lines (AsPC-1, BxPC-3, Panc-1, and MiaPaCa-2), with or without knockdown of PRLR (clustered regularly interspaced short palindromic repeats or small hairpin RNA), were incubated with PRL or penfluridol and analyzed in proliferation and spheroid formation. C57BL/6 mice were given injections of UNKC-6141 cells, with or without knockdown of PRLR, into pancreas, and tumor development was monitored for 4 weeks, with some mice receiving penfluridol treatment for 21 days. Human pancreatic tumor tissues were implanted into interscapular fat pads of NSG mice, and mice were given injections of penfluridol daily for 28 days. Nude mice were given injections of Panc-1 cells, xenograft tumors were grown for 2 weeks, and mice were then given intraperitoneal penfluridol for 35 days. Tumors were collected from mice and analyzed by histology, immunohistochemistry, and immunoblots.

RESULTS

Levels of PRLR were increased in PDAC compared with nontumor pancreatic tissues. Incubation of pancreatic cell lines with PRL activated signaling via JAK2-signal transducer and activator of transcription 3 and extracellular signal-regulated kinase, as well as formation of pancospheres and cell migration; these activities were not observed in cells with PRLR knockdown. Pancreatic cancer cells with PRLR knockdown formed significantly smaller tumors in mice. We identified several diphenylbutylpiperidine-class antipsychotic drugs as agents that decreased PRL-induced JAK2 signaling; incubation of pancreatic cancer cells with these compounds reduced their proliferation and formation of panco spheres. Injections of 1 of these compounds, penfluridol, slowed the growth of xenograft tumors in the different mouse models, reducing proliferation and inducing autophagy of the tumor cells.

CONCLUSIONS

Levels of PRLR are increased in PDAC, and exposure to PRL increases proliferation and migration of pancreatic cancer cells. Antipsychotic drugs, such as penfluridol, block PRL signaling in pancreatic cancer cells to reduce their proliferation, induce autophagy, and slow the growth of xenograft tumors in mice. These drugs might be tested in patients with PDAC.

The Histone Demethylase KDM3A, Increased in Human Pancreatic Tumors, Regulates Expression of DCLK1 and Promotes Tumorigenesis in Mice

BACKGROUND & AIMS

The histone lysine demethylase 3A (KDM3A) demethylates H3K9me1 and H3K9Me2 to increase gene transcription and is upregulated in tumors, including pancreatic tumors. We investigated its activities in pancreatic cancer cell lines and its regulation of the gene encoding doublecortin calmodulin-like kinase 1 (DCLK1), a marker of cancer stem cells.

METHODS

We knocked down KDM3A in MiaPaCa-2 and S2-007 pancreatic cancer cell lines and overexpressed KDM3A in HPNE cells (human noncancerous pancreatic ductal cell line); we evaluated cell migration, invasion, and spheroid formation under hypoxic and normoxic conditions. Nude mice were given orthotopic injections of S2-007 cells, with or without (control) knockdown of KDM3A, and HPNE cells, with or without (control) overexpression of KDM3A; tumor growth was assessed. We analyzed pancreatic tumor tissues from mice and pancreatic cancer cell lines by immunohistochemistry and immunoblotting. We performed RNA-sequencing analysis of MiaPaCa-2 and S2-007 cells with knockdown of KDM3A and evaluated localization of DCLK1 and KDM3A by immunofluorescence. We analyzed the cancer genome atlas for levels of KDM3A and DCLK1 messenger RNA in human pancreatic ductal adenocarcinoma (PDAC) tissues and association with patient survival time.

RESULTS

Levels of KDM3A were increased in human pancreatic tumor tissues and cell lines, compared with adjacent nontumor pancreatic tissues, such as islet and acinar cells. Knockdown of KDM3A in S2-007 cells significantly reduced colony formation, invasion, migration, and spheroid formation, compared with control cells, and slowed growth of orthotopic tumors in mice. We identified KDM3A-binding sites in the DCLK1 promoter; S2-007 cells with knockdown of KDM3A had reduced levels of DCLK1. HPNE cells that overexpressed KDM3A formed foci and spheres in culture and formed tumors and metastases in mice, whereas control HPNE cells did not. Hypoxia induced sphere formation and increased levels of KDM3A in S2-007 cells and in HPNE cells that overexpressed DCLK1, but not control HPNE cells. Levels of KDM3A and DCLK1 messenger RNA were higher in human PDAC than nontumor pancreatic tissues and correlated with shorter survival times of patients.

CONCLUSIONS

We found human PDAC samples and pancreatic cancer cell lines to overexpress KDM3A. KDM3A increases expression of DCLK1, and levels of both proteins are increased in human PDAC samples. Knockdown of KDM3A in pancreatic cancer cell lines reduced their invasive and sphere-forming activities in culture and formation of orthotopic tumors in mice. Hypoxia increased expression of KDM3A in pancreatic cancer cells. Strategies to disrupt this pathway might be developed for treatment of pancreatic cancer.

Pleotropic role of RNA binding protein CELF2 in autophagy induction

We previously reported that ionizing radiation (IR) mediates cell death through the induction of CUGBP elav-like family member 2 (CELF2), a tumor suppressor. CELF2 is an RNA binding protein that modulates mRNA stability and translation. Since IR induces autophagy, we hypothesized that CELF2 regulates autophagy-mediated colorectal cancer (CRC) cell death. For clinical relevance, we determined CELF2 levels in The Cancer Genome Atlas (TCGA). Role of CELF2 in radiation response was carried out in CRC cell lines by immunoblotting, immunofluorescence, autophagic vacuole analyses, RNA stability assay, quantitative polymerase chain reaction and electron microscopy. In vivo studies were performed in a xenograft tumor model. TCGA analyses demonstrated that compared to normal tissue, CELF2 is expressed at significantly lower levels in CRC, and is associated with better overall 5-year survival in patients receiving radiation. Mechanistically, CELF2 increased levels of critical components of the autophagy cascade including Beclin-1, ATG5, and ATG12 by modulating mRNA stability. CELF2 also increased autophagic flux in CRC. IR significantly induced autophagy in CRC which correlates with increased levels of CELF2 and autophagy associated proteins. Silencing CELF2 with siRNA, mitigated IR induced autophagy. Moreover, knockdown of CELF2 in vivo conferred tumor resistance to IR. These studies elucidate an unrecognized role for CELF2 in inducing autophagy and potentiating the effects of radiotherapy in CRC.

Abstract 3486: RBM3 causes differential expression lncRNA in colon cancer cell lines

Introduction: Colon cancer is the third most commonly diagnosed cancer and leading cause of cancer-related deaths in the United States. It usually begins as a benign growth that transforms into a malignant adenocarcinoma through genetic changes in tumor suppressor genes and oncogenes. Cancer stem cells are a rare group of cells within a tumor that have self-renewal capacities and with high potency for tumor relapse and metastasis. Wnt/β-catenin is one of the major pathways deregulated in colon cancer and also important in stem cell self-renewal. Wnt/β-catenin signaling is important in maintaining intestinal homeostasis and the stem cell niche, but aberrant activation of the pathway increases the stem cell population leading to aggressive cancer. We determined that RBM3 induces stem-like characteristics in colon cancer cells in part, by enhancing Wnt/β-catenin-induced GSK3β inactivation. We are further evaluating the mechanism by which RBM3 increases Wnt/ β-catenin signaling leading to increased stemness.

Methods: HCT116 and DLD1 cell lines were used in this study. We used a PCR array to identify specific Wnt pathway proteins regulated by RBM3, in HCT116 RBM3 overexpressing cells and compared it to vector control cells. RNA-IP was performed to confirm if RBM3 bound to Wnt3a and LRP6. ChIP was performed for identify β-catenin target gene cMyc. RNA seq was performed to identify differential gene expression and also differential lncRNA expression. RNA-Immunoprecipitation seq was performed to identify RBM3 protein bound cellular proteins. Ingenuity pathway analysis was performed for all the sequencing data.

Results: Our data demonstrate that several Wnt pathway genes including Wnt3a and LRP6 are upregulated in RBM3 overexpressing cells. To identify mRNA regulated by RBM3, we performed RNA-IP for RBM3. We found that RBM3 was associated with the mRNA for Wnt3a and LRP6. The ingenuity pathway analysis for RNA seq shows expression of genes involved in cell growth, proliferation and metastasis like Jun, LAMC2, Myc, NR2F2, NT5E etc. when RBM3 is overexpressed in the cells, showing a role of RBM3 in cancer progression. The seq data also shows differential expression of lncRNA especially those involved in cancer like CCAT1 and SNHG16. The ingenuity pathway analysis for RNA-IP seq also shows increase in molecules involved in proliferation and cell movement. In-vivo studies were also performed to confirm role of RBM3 in tumorigenesis.

Conclusion: RBM3 increases stemness by activating β-catenin pathway possibly through Wnt3a and LRP6. RBM3 overexpression causes differential expression of lncRNA and also increases expression of genes involved in cell growth and proliferation possibly by interacting with its target mRNAs.

Citation Format: Afreen Asif Ali Sayed, Dharmalingam Subramaniam, Shahid Umar, Sufi M. Thomas, Shrikant Anant. RBM3 causes differential expression lncRNA in colon cancer cell lines [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 3486. doi:10.1158/1538-7445.AM2017-3486

Molecular studies on chicken melanoma differentiation associated gene-9 (mda-9)

BACKGROUND

Melanoma differentiation associated (mda) genes in human encode a protein which has a surprising variety and diversity of interaction partners. It is a positive regulator of cancer cell progression in breast cancer, melanoma, and other human cancers. It regulates cell motility and invasion by altering defined biochemical and signalling pathways.

METHODS

Suppressive subtractive hybridisation (SSH) has been done using a cDNA library prepared from lipopolysaccharides (LPS) stimulated and non-stimulated chicken spleen cells. Then PCR analysis and in situ hybridisation were done for further studies.

RESULTS

This approach resulted in the identification of important chicken mda fragment. The obtained fragment was about 450bp covering the area from position 500 to position 950 of the human homologue. The expression analysis showed a wide variation in tissues and cell lines. In situ studies revealed mRNA expression in LPS stimulated tissues.

CONCLUSION

In this study a homologue for a chicken novel gene was described. The chicken melanoma differentiation associated gene-9 (mda-9) gene was found to be expressed in many tissues and cell lines in different levels. The stimulation time course was found to have a wide effect on both tissues and cell lines. The mda-9 gene was localised by in situ hybridisation and the effect of LPS stimulation was investigated.