Abstract 898: Clear cell renal cell carcinoma resistance to RTKs inhibitors is mediated by c-Met receptor and MCPIP1

Introduction

Clear cell renal cell carcinoma (ccRCC) treatment with small molecules that inhibit multiple receptor tyrosine kinases (RTKs),showed in approximately 38% of patients significant tumor control. However, despite the efficacy of treatment, ccRCC often develops resistance to targeted drugs and the majority of patients who receive such treatment exhibit progressive disease after 1 year. Several hypotheses have been proposed regarding the mechanisms underlying resistance to RTKs inhibitors, but the precise pathways have not yet been fully elucidated.

Aim

The main objective of our study was to determine the role of c-Met and anti-inflammatory protein MCPIP1 in the acquisition of resistance to RTKs inhibitors in ccRCC.

Materials and methods

ccRCC cell lines (Caki-1 and Caki-2) as well as normal epithelial cell lines (Hek293, RPTEC/TERT1) were treated with sunitinib, sorafenib or SU11274 constantly for 24h, 1 and 3 weeks. The level and localization of key proteins were examined using western blots and IF staining. ccRCC patient samples were divided into four histological grades, and levels of genes or proteins were investigated using microarray analysis, western blots, protein arrays, mass spectrometry and real time PCR.

Results

Our study shows that short term (24h) and long term (3 weeks) stimulation with sunitinib or sorafenib induced phosphorylation of c-Met receptor, STAT3 and Src kinase. Furthermore, sunitinib treatment resulted in the acquisition of cancer stem cells features and the formation of clones. In addition, after sunitinib and sorafenib treatment we observed a decrease in the protein level of MCPIP1, postulated tumor suppressor. Interestingly, after MCPIP1 overexpression, we observed c-Met downregulation, regulated by RNase activity of MCPIP1. Moreover, our results show that in patient samples, together with MCPIP1 downregulation, level of phosphorylated and total c-Met receptor increase.

Conclusions

We showed that acquisition of therapy resistance in ccRCC may be affected by MCPIP1 decrease, together with phopsphorylation of c-Met receptor and it can be partially reversed by overexpressing the MCPIP1 protein, which may act as a potent tumor suppressor. Proposed research may help in understanding the mechanisms responsible for tumor resistance to targeted therapy. Obtained results may contribute to increased understanding of the biology of clear cell renal cell carcinoma, which in the future may help in identifying new, more effective therapeutic purposes or improving existing ones.

Acknowledgment

This study was supported by research grant from the National Science Centre 2013/09/D/NZ/00249, 2017/25/N/NZ5/03014 and grant from Jagiellonian University BMN 16/2017.

Citation Format: Paulina Marona, Judyta Górka, Jolanta Jura, Katarzyna Miękus. Clear cell renal cell carcinoma resistance to RTKs inhibitors is mediated by c-Met receptor and MCPIP1 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 898.

MCPIP1 – an important RNase controlling intracellular RNA pool

Post-transcriptional regulation of mRNA pool is a key process coordinating the proper functioning of cells. This tight control of RNA molecules allows cells to quickly adapt to environmental conditions without the activation of translation. Degradation of RNA is one of the important mechanisms regulating RNA homeostasis. One of the protein involved in this process is a RNase called MCPIP1, whose function was described in 2009. The enzymatic activity of MCPIP1 is tightly linked to the zinc finger domain responsible for RNA binding and a catalytic domain that participates in endonucleolytic digestion of RNA molecules. MCPIP1 recognizes and cleaves a wide array of substrates, both endogenous mRNA, miRNA, and RNA viruses. Although MCPIP1 structure has not yet been resolved, it is known how an active center is formed and what motives in the RNA sequence are recognized and digested. MCPIP1 recognizes and cleaves RNA within the hairpin structure. Broad spectrum of MCPIP1 substrates makes this protein an important regulator of many biological processes such as inflammation, cell differentiation, tumor growth or viral infections. In this review we describe a structure, properties and biological function of RNase called MCPIP1.

Fenofibrate attenuates contact-stimulated cell motility and gap junctional coupling in DU-145 human prostate cancer cell populations

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Genistein inhibits the contact-stimulated migration of prostate cancer cells

The results of several epidemiological studies have suggested that a soybean-based diet is associated with a lower risk of prostate cancer. We investigated the effect of the soy isoflavone genistein on the proliferation and contact-stimulated migration of rat prostatic carcinoma MAT-LyLu and AT-2 cell lines. Genistein almost completely inhibited the growth of both MAT-LyLu and AT-2 cells in the concentration range from 25 to 100 muM, but the addition of 1 muM genistein to the medium significantly stimulated the proliferation of both cell lines. Additionally, at concentrations above 25 muM, genistein showed a potent cytotoxic effect. However, the central finding of this study is that at physiologically relevant concentrations (1 muM and 10 muM), genistein inhibits the motility of prostate cancer cells stimulated by homo-and heterotypic contacts. These results show that at physiological concentrations, genistein exerts an inhibitory effect on the migration of prostate cancer cells and suggest that it may be one of the factors responsible for the anti-metastatic activity of plant isoflavonoids.

Contact-activated migration of melanoma B16 and sarcoma XC cells

During migration, tumour cells interact with neighbouring neoplastic and normal host cells, and such interaction may influence their motile activity. We investigated the effect of homotypic collisions on the motile activity of two tumour cell lines, mouse melanoma B16 and rat sarcoma XC, and nontransformed human skin fibroblasts. It was found that the tumour cells show only limited motile activity when moving as single cells without contact with neighbours. At a higher density of the culture (and also at a greater number of cell to cell contacts) the activation of motility of investigated tumour cells was observed. On the other hand, the normal human skin fibroblasts showed a typical reaction of density-dependent inhibition of motility. The motile activity of tumour cells was not affected by conditioned media and was visibly dependent on a direct physical contact among colliding cells. The activation of cell movement was observed about 40–50 min after the initial contact between tumour cells. Contact-activated migration of neoplastic cells was inhibited by 50 µM verapamil (a selective voltage-gated calcium channel inhibitor) and 10 µM gadolinium chloride (a nonspecific blocker of mechanosensitive ion channels) but not by pertussis toxin. The observation that homotypic collisions among tumour cells strongly increase their motile activity suggests that contact-activated migration may play a significant role in tumour invasion and metastasis.Key words: cell movement, metastases, contact activation of cell migration, contact inhibition.