Autophagy Inhibition Enhances Sunitinib Efficacy in Clear Cell Ovarian Carcinoma.

Clear cell ovarian carcinoma (CCOC) is an aggressive form of epithelial ovarian cancer that exhibits low response rates to systemic therapy and poor patient outcomes. Multiple studies in CCOC have revealed expression profiles consistent with increased hypoxia, and our previous data suggest that hypoxia is correlated with increased autophagy in CCOC. Hypoxia-induced autophagy is a key factor promoting tumor cell survival and resistance to therapy. Recent clinical trials with the molecular-targeted receptor tyrosine kinase (RTK) inhibitor sunitinib have demonstrated limited activity. Here, it was evaluated whether the hypoxia-autophagy axis could be modulated to overcome resistance to sunitinib. Importantly, a significant increase in autophagic activity was found with a concomitant loss in cell viability in CCOC cells treated with sunitinib. Pharmacologic inhibition of autophagy with the lysosomotropic analog Lys05 inhibited autophagy and enhanced sunitinib-mediated suppression of cell viability. These results were confirmed by siRNA targeting the autophagy-related gene Atg5 In CCOC tumor xenografts, Lys05 potentiated the antitumor activity of sunitinib compared with either treatment alone. These data reveal that CCOC tumors have an autophagic dependency and are an ideal tumor histotype for autophagy inhibition as a strategy to overcome resistance to RTK inhibitors like sunitinib.Implications: This study shows that autophagy inhibition enhances sunitinib-mediated cell death in a preclinical model of CCOC. Mol Cancer Res; 15(3); 250-8. ©2017 AACR.

A novel mouse model of Campylobacter jejuni gastroenteritis reveals key pro-inflammatory and tissue protective roles for Toll-like receptor signaling during infection.

Campylobacter jejuni is a major source of foodborne illness in the developed world, and a common cause of clinical gastroenteritis. Exactly how C. jejuni colonizes its host's intestines and causes disease is poorly understood. Although it causes severe diarrhea and gastroenteritis in humans, C. jejuni typically dwells as a commensal microbe within the intestines of most animals, including birds, where its colonization is asymptomatic. Pretreatment of C57BL/6 mice with the antibiotic vancomycin facilitated intestinal C. jejuni colonization, albeit with minimal pathology. In contrast, vancomycin pretreatment of mice deficient in SIGIRR (Sigirr(-/-)), a negative regulator of MyD88-dependent signaling led to heavy and widespread C. jejuni colonization, accompanied by severe gastroenteritis involving strongly elevated transcription of Th1/Th17 cytokines. C. jejuni heavily colonized the cecal and colonic crypts of Sigirr(-/-) mice, adhering to, as well as invading intestinal epithelial cells. This infectivity was dependent on established C. jejuni pathogenicity factors, capsular polysaccharides (kpsM) and motility/flagella (flaA). We also explored the basis for the inflammatory response elicited by C. jejuni in Sigirr(-/-) mice, focusing on the roles played by Toll-like receptors (TLR) 2 and 4, as these innate receptors were strongly stimulated by C. jejuni. Despite heavy colonization, Tlr4(-/-)/Sigirr(-/-) mice were largely unresponsive to infection by C. jejuni, whereas Tlr2(-/-)/Sigirr(-/-) mice developed exaggerated inflammation and pathology. This indicates that TLR4 signaling underlies the majority of the enteritis seen in this model, whereas TLR2 signaling had a protective role, acting to promote mucosal integrity. Furthermore, we found that loss of the C. jejuni capsule led to increased TLR4 activation and exaggerated inflammation and gastroenteritis. Together, these results validate the use of Sigirr(-/-) mice as an exciting and relevant animal model for studying the pathogenesis and innate immune responses to C. jejuni.

The autophagy protein LC3A correlates with hypoxia and is a prognostic marker of patient survival in clear cell ovarian cancer.

Clear cell ovarian cancer histotypes exhibit metabolic features associated with resistance to hypoxia and glucose deprivation-induced cell death. This metabolic characteristic suggests that clear cell ovarian cancers activate survival mechanisms not typical of other epithelial ovarian cancers. Here we demonstrate that microtubule-associated protein 1 light chain 3A (LC3A), a marker of autophagy, is related to hypoxia and poor prognosis in clear cell ovarian cancer. In 485 ovarian tumours, we found that LC3A was significantly associated with poor progression-free (p = 0.0232), disease-specific (p = 0.0011) and overall patient survival (p = 0.0013) in clear cell ovarian cancer patients, but not in other subtypes examined. LC3A was an independent prognostic marker of reduced disease-specific [hazard ratio (HR): 2.55 (95% CI 1.21-5.37); p = 0.014] and overall survival [HR: 1.95 (95% CI 1.00-3.77); p = 0.049] in patients with clear cell ovarian carcinoma. We also found a strong link between autophagy and hypoxia as LC3A staining revealed a significant positive association with the hypoxia-related proteins carbonic anhydrase-IX and HIF-1α. The functional link between hypoxia and autophagy was demonstrated using clear cell and high-grade serous cell lines that were subjected to hypoxia or hypoxia + glucose deprivation. Clear cell carcinoma lines displayed greater autophagy induction and were subsequently more sensitive to inhibition of autophagy under hypoxia compared to the high-grade serous lines. Together, our findings indicate that hypoxia-induced autophagy may be crucial to the clinical pathology of clear cell ovarian cancer and is a potential explanation for histological subtype differences in patient disease progression and outcomes.

Targeting autophagy: the Achilles' heel of cancer.

In recent years, tremendous progress has been made toward unveiling the mechanism of autophagy and its exploitation by many different cancer types. This year the American Association for the Advancement of Science held a one day Symposium on Autophagy: An Emerging Therapeutic Target in Human Disease in Vancouver, British Columbia and brought together experts in cell biology, drug discovery, and clinical translation to share their research findings and prospects. Currently, autophagy is being investigated on several fronts, from modulation of gene expression to in vivo studies, and more recently clinical trials in cancer. Key topics of discussion were determining which stage of autophagy would be the ideal target for inhibition to produce the highest impact, and which cancers or cancer subtypes would be the most sensitive to autophagy inhibitors; the answers to these questions may be a turning point in cancer therapy research.