The developmental regulator SOX9 is linked to cancer progression mainly as a result of its role in the regulation of cancer stem cells (CSCs). However, its activity in the differentiated cells that constitute the heterogeneous tumor bulk has not been extensively studied. In this work, we addressed this aspect in gastric cancer, glioblastoma and pancreatic adenocarcinoma. SOX9 silencing studies revealed that SOX9 is required for cancer cell survival, proliferation and evasion of senescence in vitro and tumor growth in vivo. Gain of-SOX9 function showed that high levels of SOX9 promote tumor cell proliferation in vitro and in vivo. Mechanistically, the modulation of SOX9 changed the expression of the transcriptional repressor BMI1 in the same direction in the three types of cancer, and the expression of the tumor suppressor p21 cip in the opposite direction. In agreement with this, SOX9 expression positively correlated with BMI1 levels and inversely with p21 cip in clinical samples of the different cancers. Moreover, BMI1 re-establishment in SOX9-silenced tumor cells restored cell viability and proliferation as well as decreased p21 cip in vitro and tumor growth in vivo. These results indicate that BMI1 is a critical effector of the pro-tumoral activity of SOX9 in tumor bulk cells through the repression of p21 cip. Our results highlight the relevance of the SOX9-BMI1-p21 cip axis in tumor progression, shedding novel opportunities for therapeutic development. Some types of cancer exhibit a dismal prognosis, mainly due to its late diagnosis, its aggressive progression and the resistance to the available chemotherapy, in which inter and intra-tumoral heterogeneity play a major role 1,2. One of these types of cancer is pancreatic ductal adenocarcinoma (PDAC), with a 5-year survival rate of less than 6% 3 and very similar rates of incidence and mortality (458,918 new diagnoses and 432,242 deaths worldwide in 2018) 4. Glioblastoma (GBM), the most malignant primary brain tumor, also represents a challenge in oncology despite having a low incidence (less than 5 cases per 100,000 people), as exhibits a 5-year survival rate of 5.6% 5 and a median survival of 14.6 months 6. For its part, gastric cancer (GC) is the third leading cause of cancer deaths worldwide, with an estimated 783,000 deaths in 2018 4. SOX9 [SRY (Sex determining region Y)-box 9] is a member of the SOX family of transcription factors, which are developmental regulators characterized by a conserved high mobility group (HMG) DNA-binding domain 7. SOX9 regulates stem cell maintenance and instruction of cell fate, and exerts relevant roles during development, such as sex determination, neural crest development, chondrogenesis or pancreas development 8-10. During embryogenesis, SOX9 is expressed and regulates progenitor proliferation and differentiation, being required for maintaining tissue identity in different contexts, but mainly in the brain and gastrointestinal system 10-12. Likewise, in the adulthood, SOX9 also plays a relevant role in the maintenance of t...

Chaperone-mediated autophagy (CMA) is a homeostatic process essential for the lysosomal degradation of a selected subset of the proteome. CMA activity directly depends on the levels of LAMP2A, a critical receptor for CMA substrate proteins at the lysosomal membrane. In glioblastoma (GBM), the most common and aggressive brain cancer in adulthood, high levels of LAMP2A in the tumor and tumor-associated pericytes have been linked to temozolomide resistance and tumor progression. However, the role of LAMP2A, and hence CMA, in any cancer stem cell type or in glioblastoma stem cells (GSC) remains unknown. In this work, we show that LAMP2A expression is enriched in patient-derived GSCs, and its depletion diminishes GSC-mediated tumorigenic activities.Conversely, overexpression of LAMP2A facilitates the acquisition of GSC properties. Proteomic and transcriptomic analysis of LAMP2A-depleted GSCs revealed reduced extracellular matrix (ECM) interaction effectors in both analyses. Moreover, pathways related to mitochondrial metabolism and the immune system were differentially deregulated at the proteome level. Furthermore, clinical samples of GBM tissue presented with overexpression of LAMP2, which correlated with advanced glioma grade and poor overall survival. In conclusion, these results identify a novel role of CMA in directly regulating GSCs activity via multiple pathways at the proteome and transcriptome levels. SIGNIFICANCEA receptor of chaperone-mediated autophagy regulates glioblastoma stem cells and may serve as a potential biomarker for advanced tumor grade and poor survival in this disease.Research.

Gastric cancer (GC) is the fourth leading cause of cancer death worldwide, with an average 5-year survival rate of 32%, being of 6% for patients presenting distant metastasis. Despite the advances made in the treatment of GC, chemoresistance phenomena arise and promote recurrence, dissemination and dismal prognosis. In this context, gastric cancer stem cells (gCSCs), a small subset of cancer cells that exhibit unique characteristics, are decisive in therapy failure. gCSCs develop different protective mechanisms, such as the maintenance in a quiescent state as well as enhanced detoxification procedures and drug efflux activity, that make them insusceptible to current treatments. This, together with their self-renewal capacity and differentiation ability, represents major obstacles for the eradication of this disease. Different gCSC regulators have been described and used to isolate and characterize these cell populations. However, at the moment, no therapeutic strategy has achieved the effective targeting of gCSCs. This review will focus on the properties of cancer stem cells in the context of therapy resistance and will summarize current knowledge regarding the impact of the gCSC regulators that have been associated with GC chemoradioresistance.

Resistance of melanoma to targeted therapy and immunotherapy is linked to metabolic rewiring. Here, we show that increased fatty acid oxidation (FAO) during prolonged BRAF inhibitor (BRAFi) treatment contributes to acquired therapy resistance in mice. Targeting FAO using the US Food and Drug Administration-approved and European Medicines Agency-approved anti-anginal drug ranolazine (RANO) delays tumour recurrence with acquired BRAFi resistance. Single-cell RNA-sequencing analysis reveals that RANO diminishes the abundance of the therapy-resistant NGFRhi neural crest stem cell subpopulation. Moreover, by rewiring the methionine salvage pathway, RANO enhances melanoma immunogenicity through increased antigen presentation and interferon signalling. Combination of RANO with anti-PD-L1 antibodies strongly improves survival by increasing antitumour immune responses. Altogether, we show that RANO increases the efficacy of targeted melanoma therapy through its effects on FAO and the methionine salvage pathway. Importantly, our study suggests that RANO could sensitize BRAFi-resistant tumours to immunotherapy. Since RANO has very mild side-effects, it might constitute a therapeutic option to improve the two main strategies currently used to treat metastatic melanoma.

Supplementary Table from Chaperone-Mediated Autophagy Controls Proteomic and Transcriptomic Pathways to Maintain Glioma Stem Cell Activity