Panneerdoss Subbarayalu

Abstract B01: MicroRNAs as novel therapeutic adjuvants to treat high-risk medulloblastoma.

Medulloblastoma is the most common malignant brain tumor in children, accounting for 18% of newly diagnosed brain tumors and 10% of all children cancer-related deaths. Despite improvement in the 5-year survival rate of medulloblastoma in recent years, only a small percentage of patients survive high-risk metastatic disease. The quality of life for those who do survive is often substantially reduced due to the toxicity associated with radiation and chemotherapy. Vincristine is a microtubule-destabilizing antimitotic drug, which is routinely administered in higher dosages to both high and average risk medulloblastoma patients. As a result, these patients suffer from devastating neurotoxic effects that include but not limited to: sensorimotor and autonomic neuropathy, hearing loss, mononeuropathy, and seizures. Using high-throughput microRNA mimic library screens, we identified a group of microRNAs that may improve the efficacy of vincristine against c-MYC amplified medulloblastoma as well as re-sensitize vincristine-resistant medulloblastoma. Our findings revealed that these microRNAs may act as tumor suppressors since their overexpression inhibited colony formation, migration and invasion ability of medulloblastoma cells. Furthermore, these microRNAs suppressed stem cell renewal/proliferation of c-MYC amplified medulloblastoma cells. Expression analysis, gene enrichment analysis and target prediction algorithms revealed that these microRNAs exert their vincristine sensitizing and tumor suppressor effect by targeting genes involved in microtubule organization, cell cycle regulation, DNA damage repair and mRNA translation. One of our most interesting targets is EIF4E3, which is a translation initiation factor. Our preliminary findings indicate that EIF4E3 may regulate medulloblastoma cell growth, progression and vincristine sensitivity by modulating c-MYC translation. Further experiments are underway to test the potential of candidate miRNA and EIF4E3 as vincristine sensitizer in vivo. In conclusion, this study may identify novel factors that have potential not only to decrease the current therapeutic dose of vincristine and therefore eliminate its side effects, but also have potential to multiply the efficacy of lower doses in order to overcome hard to treat high-risk tumors. Citation Format: Nourhan Abdelfattah, Panneerdoss Subbarayalu, Benjamin Onyeagucha, Subapriya Rajamanickam, Hung-I Harry Chen, Manjeet Rao. MicroRNAs as novel therapeutic adjuvants to treat high-risk medulloblastoma.. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Pediatric Cancer Research: From Mechanisms and Models to Treatment and Survivorship; 2015 Nov 9-12; Fort Lauderdale, FL. Philadelphia (PA): AACR; Cancer Res 2016;76(5 Suppl):Abstract nr B01.

Novel post-transcriptional and post-translational regulation of pro-apoptotic protein BOK and anti-apoptotic protein Mcl-1 determine the fate of breast cancer cells to survive or die

Deregulation of apoptosis is central to cancer progression and a major obstacle to effective treatment. The Bcl-2 gene family members play important roles in the regulation of apoptosis and are frequently altered in cancers. One such member is pro-apoptotic protein Bcl-2-related Ovarian Killer (BOK). Despite its critical role in apoptosis, the regulation of BOK expression is poorly understood in cancers. Here, we discovered that miR-296-5p regulates BOK expression by binding to its 3’-UTR in breast cancers. Interestingly, miR-296-5p also regulates the expression of anti-apoptotic protein myeloid cell leukemia 1 (Mcl-1), which is highly expressed in breast cancers. Our results reveal that Mcl-1 and BOK constitute a regulatory feedback loop as ectopic BOK expression induces Mcl-1, whereas silencing of Mcl-1 results in reduced BOK levels in breast cancer cells. In addition, we show that silencing of Mcl-1 but not BOK reduced the long-term growth of breast cancer cells. Silencing of both Mcl-1 and BOK rescued the effect of Mcl-1 silencing on breast cancer cell growth, suggesting that BOK is important for attenuating cell growth in the absence of Mcl-1. Depletion of BOK suppressed caspase-3 activation in the presence of paclitaxel and in turn protected cells from paclitaxel-induced apoptosis. Furthermore, we demonstrate that glycogen synthase kinase (GSK3) α/β interacts with BOK and regulates its level post-translationally in breast cancer cells. Taken together, our results suggest that fine tuning of the levels of pro-apoptotic protein BOK and anti-apoptotic protein Mcl-1 may decide the fate of cancer cells to either undergo apoptosis or proliferation.

Abstract 2336: Novel regulatory mechanisms for Bcl2-related Ovarian Killer (BOK) expression in breast cancer

Deregulation of apoptosis is central to cancer progression and a major obstacle to effective treatment. The Bcl-2 gene family members play important roles in the regulation of apoptosis and are frequently altered in cancers. One such member is Bcl-2-related Ovarian Killer (BOK), which is a pro-apoptotic protein. Despite its critical role in apoptosis, the regulation of BOK expression is poorly understood in cancers. Here, we discovered that miR-296-5p, regulates BOK expression by binding to its 3’UTR in breast cancers. Furthermore, we show that depletion of BOK by either miR-296-5p or siRNA against BOK protected breast cancer cells from undergoing paclitaxel-induced apoptosis. Interestingly, miR-296-5p also regulates the expression of Mcl-1, which is an anti-apoptotic protein and is highly expressed in breast cancers. Our results reveal that Mcl-1 is important for suppression of BOK function as ectopic BOK expression induced Mcl-1, while silencing of BOK resulted in reduced Mcl-1 levels in breast cancer cells. In addition, we show that specific silencing of Mcl-1 reduced the long-term growth of breast cancer cells, whereas BOK inhibition didn’t have any effect on the growth of breast cancer cells. Surprisingly, silencing of both Mcl-1 and BOK rescued the effect of Mcl-1 silencing on breast cancer cell growth, suggesting that BOK is important for attenuating cell growth in the absence of Mcl-1, and also showing a tight feedback regulatory loop between BOK and Mcl-1 in breast cancer cells. Furthermore, we demonstrated that BOK protein level is regulated post-translationally by GSK3α and to some extent GSK3β as GSK3 inhibitor (CHIR99021) or silencing of GSK3 significantly increased BOK protein levels in breast cancer cells. Notably, we found that Mcl-1 interacts with GSK3α/β and silencing of Mcl-1 using siRNA significantly attenuated endogenous GSK3α/β levels in breast cancer cells. Taken together, our results suggest that fine tuning (either post-transcriptionally by miR-296-5p or post-translationally by GSK3) of the levels of pro-apoptotic protein BOK and anti-apoptotic protein Mcl-1 decide the fate of cancer cells to either undergo Apoptosis or proliferation. Citation Format: Benjamin Chidi Onyeagucha, Panneerdoss Subbarayalu, Subapriya Rajamanickam, Nourhan Abdelfattah, Santosh Timilsina, Rosa M. Guzman, Carla Zeballos, Vijay Eedunuri, Sanjay Bansal, Hima Bansal, Tabrez A. Mohammad, Yidong Chen, Manjeet K. Rao. Novel regulatory mechanisms for Bcl2-related Ovarian Killer (BOK) expression in breast cancer [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 2336. doi:10.1158/1538-7445.AM2017-2336

Abstract 3658: A novel microtubule associated RNA binding protein matrin 3 act as a tumor suppressor by regulating mitotic spindle organizing proteins in triple negative breast cancers

Microtubule-targeting drugs are widely used as cancer chemotherapeutic agents and they have been shown to inhibit mitotic progression and interphase signaling. Despite their use as a first line treatment for cancer, many patients develop resistance to microtubule-targeting drugs leading to early relapse and shorter survival. Moreover, the quality of life for patients who do survive is often substantially reduced due to the toxicity associated with these drugs. Therefore, identification of new factors that determine the effectiveness of microtubule-targeting agents will not only facilitate a better understanding of the mechanisms of acquired drug resistance but will also be amenable to therapeutic interventions. We discovered a novel microtubule associated protein “Matrin 3 (MATR3)” that is known to bind to RNA and play a critical role in RNA transport and RNA stabilization. Our results revealed that MATR3 acts as a potent tumor suppressor as it inhibits long-term growth, migration, invasion as well as tumor growth of triple negative breast cancer (TNBC) cells in vivo. We demonstrated that MATR3 overexpression induced cell cycle arrest and apoptosis in TNBC cells. Furthermore, analysis of breast cancer samples showed a significantly lower expression of MATR3 when compared to normal adjacent tissues. Importantly, our RNA immunoprecipitation (RIP)-seq analysis showed that MATR3 controls expression of several mitotic spindle organizing proteins by binding to their RNA. Interestingly, we found that these MATR3 regulated proteins were highly altered in breast cancer patients. In conclusion, we identified a novel RNA-binding protein that inhibits breast cancer growth and progression suppressor by regulating microtubule dynamics. Citation Format: Panneerdoss Subbarayalu, Subapriya Rajamanickam, Suryavathi Viswanadhapalli, Benjamin C. Onyeagucha, Vijay K. Eedunuri, Nicholas Dybdal-Hargreaves, Santosh Timilsina, Hima Bansal, Sanjay Bansal, Tabrez Mohammad, Yidong Chen, John C. Herr, Susan L. Mooberry, Manjeet K. Rao. A novel microtubule associated RNA binding protein matrin 3 act as a tumor suppressor by regulating mitotic spindle organizing proteins in triple negative breast cancers. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3658.

Abstract P2-03-04: Down-regulation of Bcl2-related ovarian killer (BOK) by miR-296-5p protects breast cancer cells from paclitaxel-induced apoptosis

Accumulating evidence shows that miRNAs play a role in drug resistance. Despite these observations, little is known about the identities of the miRNAs involved in drug resistance and their downstream targets. In the present study, we identified miR-296-5p for which a tumor suppressive role has been previously described, as a miRNA that is involved in paclitaxel drug resistance in triple negative breast cancer (TNBC) cells. Enforced expression of miR-296-5p suppressed cell growth, migration, and invasion in MDA-MB-231 breast cancer cells. Using a microarray approach, we identified BCL2-related Ovarian Killer (BOK), a pro-apoptotic gene as a target of miR-296-5p. BOK levels were validated BOK levels in miR-296-5p transfected MDA-MB-231 and MDA-MB-468 cells using real-time PCR and Western blot. Our results demonstrated that over-expression of miR-296-5p down-regulated BOK expression in TNBC cells. Transfection of miR-296-5p significantly suppressed luciferase reporters containing wild-type BOK-39-UTR constructs. In contrast, mutant BOK-39-UTR constructs were unaffected by ectopic miR-296-5p. Furthermore, BOK expression was induced in the presence of paclitaxel, but ectopic miR-296-5p significantly suppressed BOK induction by paclitaxel treatment compared to the control cells. These data provide new insights on the role of miRNAs in drug resistance and suggests that therapeutic strategies against miR-296-5p may be warranted. Citation Format: Onyeagucha BC, Rajamanickam S, Subbarayalu P, Bansal B, Bansal H, Chang Y-F, Timilsina S, Abdelfaltah N, Eedunuri VK, Rao MK. Down-regulation of Bcl2-related ovarian killer (BOK) by miR-296-5p protects breast cancer cells from paclitaxel-induced apoptosis. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P2-03-04.

Abstract 1787: Imipramine blue: a novel NOX inhibitor as potent therapeutic agent to treat triple-negative breast cancers

Proceedings: AACR 106th Annual Meeting 2015; April 18-22, 2015; Philadelphia, PA Breast cancer is the most common cancer in women and the second leading cause of cancer death in US. Triple-negative breast cancers (TNBC) are the most aggressive forms of breast cancer. Almost 60% of patients with TNBCs develop chemo-resistance, leading to early relapse and shorter survival. The family of NADPH oxidases (NOX) enzymes is more abundant source of reactive oxygen species, which generally over expressed in a wide range of cancers including breast cancer. Over expression of NOX family of proteins in the tumor cells and stroma results in the activation of several intracellular pathways that promotes neoplastic transformation. Moreover, NOX is an important metabolic enzyme that plays a critical role in supporting increased glycolysis in cancer cells by generating NAD+, a substrate for one of the key glycolytic reactions. The constitutive upregulation of glycolysis is thought to confer significant growth advantage to cancer cells leading to uncontrolled proliferation and increased invasion. This is especially true for TNBC that shows a strong association with the Warburg effect. Herein we evaluated first time the role of imipramine blue (IB), a NOX inhibitor and a derivative of the FDA approved antidepressant imipramine in TNBC cells growth and progression. Our results demonstrated that imipramine blue inhibits TNBC, MDA-MB-231, MDA-MB-468 and Bt-549 cells growth without affecting normal mammary epithelial (MCF-10A) cells. Notably, our studies revealed that imipramine blue targets multiple NOX family members, which are highly expressed in breast tumors when compared to adjacent normal tissue. Imipramine blue treatment also reduced migration and invasion and inhibited the self-renewal capability of MDA-MB-231 cells. Importantly, imipramine blue treatment significantly reduced experimental lung metastasis of MDA-MB-231 cells in athymic nude mice without induce apparent toxicity. Our gene microarray results further showed that IB treatment significantly altered an array of genes, including FOXM1, Aurora kinase A (AURAK) and Polo-like kinase 1 (PLK1), which play important roles in cancer growth and progression as well as in mediating sensitivity/resistance of paclitaxel (PTX), a chemotherapy drug that is routinely used as a first line treatment for breast cancer patients. Taken together, our findings propose NOX inhibitor imipramine blue as a novel therapeutic agent with less toxicity to treat triple negative breast cancers. Citation Format: Subapriya Rajamanickam, Panneerdoss Subbarayalu, Santhosh Timilsina, Michael T. Drake, Zhenze Zhao, Hung I Harry Chen, Yidong Chen, Jack L. Arbiser, Manjeet K K. Rao. Imipramine blue: a novel NOX inhibitor as potent therapeutic agent to treat triple-negative breast cancers. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1787. doi:10.1158/1538-7445.AM2015-1787

Abstract P5-10-16: miRNAs as novel therapeutic adjuvants for the prognosis and treatment of triple negative breast cancers

Approximately 15–20% of all breast cancers account for triple negative breast cancers (TNBCs) that exhibit an aggressive, distinct metastatic pattern and poor prognosis resulting in a disproportionate number of breast cancer deaths. More than 50% of patients with TNBC develop chemoresistance and do not respond to chemotherapeutic drugs, leading to early relapse and shorter survival. Understanding the mechanisms underlying such resistance is therefore crucial for the development of new, efficacious cancer drugs. In spite of extensive inquiry in this field, little is known about the key molecules/signaling pathways that regulate this phenomenon. Recently, we have discovered that small non-coding RNAs-miRNAs play critical roles in mediating drug sensitivity/resistance in TNBCs. We have identified miRNAs that are differentially expressed between chemo-resistant and sensitive breast cancer cells. In particular, through high-throughput miRNA inhibitor library screens, we have identified miRNA inhibitors that sensitize resistant TNBC cells to paclitaxel, a drug commonly used to treat triple negative breast cancers. Interestingly, our studies revealed that specific miRNAs including miR-185 (patent pending) that sensitize resistant TNBCs to paclitaxel are expressed at significantly lower levels in relapsed metastatic TNBC patient sera compared to sera from their healthy siblings. Furthermore, using liposome- or biocompatible PLGA nanoparticle-based approaches, we show that systemic delivery of one of the sensitizer miRNAs suppresses breast cancer lung metastasis without any hepatotoxicity in preclinical mouse tumor models. Importantly, we show that one of the mechanisms by which sensitizer miRNAs regulate paclitaxel sensitivity is by targeting Stathmin, a microtubule destabilizer protein that can bind to tubulin dimers and stimulate microtubule destabilization. These findings suggest that tumor-specific miRNAs render selective cell cytotoxicity in a drug-specific manner, that these miRNAs may serve as detection markers for identifying patients who might benefit most from specific drug treatment, and that these miRNAs may represent novel therapeutic tools for the treatment of the TNBCs. Since miRNAs are endogenously expressed and can be easily manipulated using synthetic oligoribonucleotides, we believe that they represent more attractive targets than the single gene or gene product targeted by conventional cancer treatments that are typically prone to drug resistance. Since paclitaxel is used for the treatment of many cancers, the long-term implications of this study are likely not limited to breast cancer alone but may apply to other tumor types. Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P5-10-16.