Abstract 3311: Autocrine and paracrine IL-4 maintains breast cancer stem cells traits via RAS/MAPK/DUSP pathway

Background: Despite the advent of successful treatment of localized malignancies, metastatic cancer still lacks efficacious therapeutic approaches, including breast cancer. It is now well established that within malignant tumors Cancer Stem Cells (CSCs) constitute a unique cell subset that fuel and succeed at tumor growth and metastases formation. Tumor microenvironment sustains CSCs characteristics, making the molecular mechanisms driving tumor progression and recurrence more complex and difficult to elucidate. Furthermore, the interaction that occurs between CSCs and the nearby stroma has proven to enhance the aggressive behavior of several carcinomas through the secretion of microenvironmental cytokines. In this context, IL-4 has already been described to promote survival of cancer cells through the up-regulation of several anti-apoptotic factors. However, still little is known about its role in promoting breast cancer progression. Results: Here we show for the first time that autocrine and paracrine production of IL-4 regulates breast CSCs (BCSCs) features, including cell proliferation, motility and cytoskeletal organization via RAS/MAPK pathway. Interestingly, relief from IL-4 impaired BCSCs proliferation, colony forming efficiency and in vivo tumor formation, while it fostered the expression of the dual specificity phosphatase-4 (DUSP4) in triple-negative basal-like BCSCs, leading to the decrease of CD44+/CD24- population. DUSP4 is commonly deficient in the most aggressive breast cancers, such as the basal-like subtype. Likewise, we observed that the enforced expression of DUSP4 increases the CD24+ compartment in basal-like BCSCs, determining also a dramatic decrease of their proliferation, colony forming efficiency, invasiveness and metastases formation. Contrarily, in luminal-like BCSCs, DUSP4 suppression favors BCSCs cell traits, including their tumorigenic and metastagenic properties. Methods: Patient-derived BCSCs were obtained by digestion of breast cancer tissues and plated in serum-free media with bFGF and EGF. DUSP4 were inserted into the p-Lenti expression vector. Stable DUSP4 knockdown was produced by lentiviral transduction of the pGFP-C vector. IL-4 function was impaired by using a high affinity IL-4Rα antagonist. To assess tumorigenicity and metastases formation, BCSCs were suspended in matrigel and injected either orthotopically or intra caudal in NOD/SCID mice. Conclusions: These findings will shed light on the molecular basis of cancer progression and on the complex crosstalk occurring between tumor and its microenvironment. The identification of tumor-related molecular events, such as the IL-4 activated signaling, might be clinically exploited as therapeutic targets in the adjuvant setting and synergize the effect of conventional chemotherapy in patients affected by breast cancers with limited therapeutic options, such as triple-negative breast cancers. Citation Format: Alice Turdo, Miriam Gaggianesi, Tiziana Apuzzo, Antonina Benfante, Aurora Chinnici, Alessandro Giammona, Simone Di Franco, Giorgio Stassi, Matilde Todaro. Autocrine and paracrine IL-4 maintains breast cancer stem cells traits via RAS/MAPK/DUSP pathway. [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 3311.