Elimination of Vitamin D Signaling Causes Increased Mortality in a Model of Overactivation of the Insulin Receptor: Role of Lipid Metabolism.

Vitamin D (VD) deficiency has been associated with cancer and diabetes. Insulin signaling through the insulin receptor (IR) stimulates cellular responses by activating the PI3K/AKT pathway. PTEN is a tumor suppressor and a negative regulator of the pathway. Its absence enhances insulin signaling leading to hypoglycemia, a dangerous complication found after insulin overdose. We analyzed the effect of VD signaling in a model of overactivation of the IR. We generated inducible double KO (DKO) mice for the VD receptor (VDR) and PTEN. DKO mice showed severe hypoglycemia, lower total cholesterol and increased mortality. No macroscopic tumors were detected. Analysis of the glucose metabolism did not show clear differences that would explain the increased mortality. Glucose supplementation, either systemically or directly into the brain, did not enhance DKO survival. Lipidic liver metabolism was altered as there was a delay in the activation of genes related to ß-oxidation and a decrease in lipogenesis in DKO mice. High-fat diet administration in DKO significantly improved its life span. Lack of vitamin D signaling increases mortality in a model of overactivation of the IR by impairing lipid metabolism. Clinically, these results reveal the importance of adequate Vitamin D levels in T1D patients.

Autophagy orchestrates adaptive responses to targeted therapy in endometrial cancer.

Targeted therapies in endometrial cancer (EC) using kinase inhibitors rarely result in complete tumor remission and are frequently challenged by the appearance of refractory cell clones, eventually resulting in disease relapse. Dissecting adaptive mechanisms is of vital importance to circumvent clinical drug resistance and improve the efficacy of targeted agents in EC. Sorafenib is an FDA-approved multitarget tyrosine and serine/threonine kinase inhibitor currently used to treat hepatocellular carcinoma, advanced renal carcinoma and radioactive iodine-resistant thyroid carcinoma. Unfortunately, sorafenib showed very modest effects in a multi-institutional phase II trial in advanced uterine carcinoma patients. Here, by leveraging RNA-sequencing data from the Cancer Cell Line Encyclopedia and cell survival studies from compound-based high-throughput screenings we have identified the lysosomal pathway as a potential compartment involved in the resistance to sorafenib. By performing additional functional biology studies we have demonstrated that this resistance could be related to macroautophagy/autophagy. Specifically, our results indicate that sorafenib triggers a mechanistic MAPK/JNK-dependent early protective autophagic response in EC cells, providing an adaptive response to therapeutic stress. By generating in vivo subcutaneous EC cell line tumors, lung metastatic assays and primary EC orthoxenografts experiments, we demonstrate that targeting autophagy enhances sorafenib cytotoxicity and suppresses tumor growth and pulmonary metastasis progression. In conclusion, sorafenib induces the activation of a protective autophagic response in EC cells. These results provide insights into the unopposed resistance of advanced EC to sorafenib and highlight a new strategy for therapeutic intervention in recurrent EC.

Effects of the multikinase inhibitors Sorafenib and Regorafenib in PTEN deficient neoplasias.

The phosphatidylinositol 3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/AKT/mTOR) axis is frequently dysregulated in cancer due to mutations in different nodes of the pathway or constitutive activation of receptor tyrosine kinases. Multikinase inhibitors as sorafenib and regorafenib represent a therapeutic approach for the treatment of these types of tumours. In the present study, we have evaluated the anti-tumoural effects of Sorafenib and Regorafenib on endometrial, prostate and thyroid neoplasias. Both inhibitors reduced cell viability in vitro and lead to a disruption of the PI3K/AKT/mTOR pathway. In vivo, we have demonstrated that Sorafenib and Regorafenib reduce thyroid hyperplasias induced by the loss of phosphatase and tensin homolog deleted on chromosome 10 (PTEN), although none of the treatments eliminated the disease. Altogether, we present the first study that correlates the response to multikinase inhibitors with a specific mutation. Moreover, this is the first report characterising the response to Regorafenib in thyroid, prostate and endometrial neoplasias.