Abstract 137: Tumor-associated ECM induces renal cell carcinoma tumorigenic responses via α6β1-integrin regulation of ITPKA
Authors: Gupta Vivekanand , Franco-Barraza Janusz , Shah Neelima , Dulaimi Essel , Zhou Yan , Devarajan Karthik , Cai Kathy Q. , Alpaugh Katherine R. , Uzzo Robert G. , Cukierman Edna 
Published: May 2015

It is estimated that over 65,150 patients were diagnosed with renal cell carcinoma (RCC) with 13,680 deaths in 2013. Surgery and targeted therapies have limited impact on survival in patients with advanced metastatic RCC. Tumor-stroma plays a pivotal role in RCC tumorigenesis including metastasis. One of the striking features of RCC is a fibro vascular stromal reaction with an altered tumor-associated extracellular matrix (TA-ECM) that directly intercalates with the tumoral epithelia playing a functional role in RCC progression. We previously suggested that stromal activation characterized by the expression of specific tumor-associated stromal proteins and the TA-ECM not only constitutes an independent worse prognostic marker, but also comprises a predictive risk indicator of recurrent RCC.

Our work is based on the fact that stromal-tumor interactions are most readily studied in in vivo-mimetic 3D models. Among the most promising systems are in vitro 3D stromal models developed by our group in which tumor cells are plated within TA-ECMs derived from fibroblasts harvested from surgical tissue samples comprised of patient-matched normal and tumor-associated fibroblasts. We have demonstrated the physiological relevance of this system in vivo and found that mesenchymal RCC stromal cells and matrices are modified during epithelial tumor progression.

Here we show that ECMs produced by normal fibroblasts are restrictive, while syngeneic tumor-associated ECMs induce increased RCC tumorigenic responses including tumor growth, resistance to apoptosis and promotion of invasion. An unbiased gene expression array was conducted using RNA obtained from RCC cells cultured within the assorted ECMs. Classic RCC signaling pathways were evident, and in addition proteins previously unsuspected to play important roles in stromal regulation of RCC progression were identified. Amid these, we observed significant increases in the levels of inositol 1,4,5-trisphosphate 3-kinase-A (IP3KA; also known as ITPKA). Our data suggests that ITPKA's activity is necessary for the above-stated TA-ECM induced tumorigenic responses. The study describes how, in response to tumor-associated but not normal ECM, α6β1-integrin activity regulates ITPKA via increased cytosolic Ca2+ stabilizing constitutive Raf1 and Erk1/2 activities to promote tumorigenic responses. Moreover, in vitro experiments were confirmed using the original patient samples while clinical relevance was established in a well-annotated RCC tissue microarray cohort.

We propose that activated stromal RCC triggers a novel α6β1/ITPKA/Erk1/2 pro-tumorigenic signaling pathway. In consequence, patients presenting activated stroma, together with high tumoral α6β1-integrin and/or ITPKA expression, are predicted to present unfavorable outcomes. This work is expected to facilitate future clinical testing of the new targets to aid development of novel RCC therapeutics.

Citation Format: Vivekanand Gupta, Janusz Franco-Barraza, Neelima Shah, Essel Dulaimi, Yan Zhou, Karthik Devarajan, Kathy Q. Cai, Katherine R. Alpaugh, Robert G. Uzzo, Edna Cukierman. Tumor-associated ECM induces renal cell carcinoma tumorigenic responses via α6β1-integrin regulation of ITPKA. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 137. doi:10.1158/1538-7445.AM2014-137