No abstract

Epidemiological evidence has linked the development and progression of several cancers including melanoma with obesity. However, whether obesity impinges on responses of cancer cells to treatment remains less understood. Here we report that human adipocytes contribute to resistance of melanoma cells to various therapeutic agents. Exposure to media from adipocyte cultures (adipocyte media) increased cell proliferation and reduced sensitivity of melanoma cells to apoptosis induced by diverse chemotherapeutic drugs, including the DNA-damaging drug cisplatin, the microtubuletargeting agent docetaxel, and the histone deacetylase inhibitor SAHA. This was associated with increased activation of PI3K/Akt and MEK/ERK signaling, and was attenuated by a PI3K or MEK inhibitor. The effect of adipocyte media on melanoma cells was, at least in part, due to the interaction between the adipokine leptin and its long form receptor OB-Rb, in that immunodepletion of leptin in adipocyte media or siRNA knockdown of OB-Rb in melanoma cells reversed the increase in Akt and ERK activation, enhancement in cell proliferation, and importantly, protection of melanoma cells against the drugs. In support, recombinant leptin partially recapitulated the effect of adipocyte media on melanoma cells. Of note, OB-Rb was increased on the surface of melanoma cells compared to melanocytes, whereas leptin short form receptors appeared to be suppressed post-transcriptionally, suggesting that OB-Rb was selectively upregulated in melanoma cells. Collectively, these results indicate that adipocytes contribute to the resistance of melanoma cells to chemotherapeutic drugs and agents targeting the PI3K/Akt and MEK/ERK pathways, and suggest that inhibition of the leptin/ OB-Rb system may be useful to improve the efficacy of multiple therapeutic approaches in the treatment of melanoma.

Chondrosarcoma is a common kind of bone cancers, and it may develop distant metastasis, followed by a significant decline in overall survival. However, there are still no specific therapeutic methods for it today. For tumors to metastasis, angiogenesis and lymphangiogenesis are both important in the early processes. Therefore, inhibiting the development of angiogenesis and lymphangiogenesis could be a method to decline tumor metastasis. Resistin was discovered as an adipocyte-secreting adipokine, which may play a critical role in modulating cancer pathogenesis. In our lab, we previously found that resistin appears to increase MMP-2 expression and then promotes metastasis in human chondrosarcoma cells. Nevertheless, the role of resistin in angiogenesis and lymphangiogenesis of human chondrosarcoma is still unknown. To examine angiogenetic and lymphangiogenetic effects of resistin, we used human endothelial progenitor cells (EPCs) and lymphatic endothelial cells (LECs) to mimic capillary and lymphatic vessels formation. The results indicated that resistin-treated chondrosarcoma cell lines promoted EPCs VEGF-A-dependent as well as LECs VEGF-C-dependent tube formation and cell migration. Then we confirmed that treating cells with resistin increased VEGF-A and VEGF-C expression in human chondrosarcoma cell lines. Moreover, we found resistin-induced VEGF-A and VEGF-C expressions are mediated by PI3K/AKT signaling and by the activation of c-Src separately. In addition, resistin decreased the expression of miR-16-5p via PI3K/AKT pathway, and so of miR-186 via c-Src. We also demonstrated that miR-186 directly targeted on VEGF-C 3’ untranslated region, and regulated the VEGF-C production. Besides, we found the expressions of resistin, VEGF-A and VEGF-C was higher in human chondrosarcoma biopsy tissues than those in normal cartilage. Taken together, resistin not only promotes human chondrosarcoma angiogenesis through the activation of PI3K/AKT signaling pathway and down-regulating miR-16-5p expression, but also promotes human chondrosarcoma lymphangiogenesis through the activation of c-Src and down-regulating miR-186. Consequently, resistin may represent a potential novel molecular therapeutic target for human chondrosarcoma therapeutic treatment. Citation Format: Meng-Ju Chi, Chih-Yang Lin, Chih-Hsin Tang. Resistin induces angiogenesis and lymphangiogenesis in human chondrosarcoma [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 1817. doi:10.1158/1538-7445.AM2017-1817

Chondrosarcoma is a kind of commonly found bone malignant tumor. The development of distant metastasis often leads to a significant decline in overall survival, and there are no specific therapeutic methods for it until today. For tumors to metastasize, angiogenesis and lymphangiogenesis are both important steps in the early periods. Resistin was discovered as an adipocyte-secreting adipokine, which may play a critical role in modulating cancer pathogenesis. However, the role of resistin in the angiogenesis and lymphangiogenesis of human chondrosarcoma is largely unknown. In our lab, we found that the expression of resistin was higher in chondrosarcoma biopsy tissues than in normal cartilage. We also confirmed that treated cells with resistin increased VEGFA and VEGFC expression, promoting angiogenesis as well as lymphangiogenesis in human chondrosarcoma cells. Moreover, the inhibitors and siRNAs of c-Src, PI3K, and AKT reduced the resistin-increased cell angiogenesis and lymphangiogenesis. Our results indicate that resistin promotes chondrosarcoma angiogenesis and lymphangiogenesis by the increasing VEGFA and VEGFC expression through the activation of the c-Src/PI3K/AKT signaling pathway expression. Therefore, resistin may represent a potential novel molecular therapeutic target for chondrosarcoma therapeutic treatment. Citation Format: Meng-Ju Chi, Hsiao-Chi Tsai, Chih-Hsin Tang. Resistin promotes tumor angiogenesis and lymphangiogenesis through c-Src/PI3K/AKT signaling pathway in human chondrosarcoma cells. [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 3363.