Calix[6]arene bypasses human pancreatic cancer aggressiveness: downregulation of receptor tyrosine kinases and induction of cell death by reticulum stress and autophagy.

Pancreatic cancer ranks fourth among cancer-related causes of death in North America. Minimal progress has been made in the diagnosis and treatment of patients with late-stage tumors. Moreover, pancreatic cancer aggressiveness is closely related to high levels of pro-survival mediators, which can ultimately lead to rapid disease progression, resistance and metastasis. The main goal of this study was to define the mechanisms by which calix[6]arene, but not other calixarenes, efficiently decreases the aggressiveness of a drug resistant human pancreas carcinoma cell line (Panc-1). Calix[6]arene was more potent in reducing Panc-1 cell viability than gemcitabine and 5-fluorouracil. In relation to the underlying mechanisms of cytotoxic effects, it led to cell cycle arrest in the G0/G1 phase through downregulation of PIM1, CDK2, CDK4 and retinoblastoma proteins. Importantly, calix[6]arene abolished signal transduction of Mer and AXL tyrosine kinase receptors, both of which are usually overexpressed in pancreatic cancer. Accordingly, inhibition of PI3K and mTOR was also observed, and these proteins are positively modulated by Mer and AXL. Despite decreasing the phosphorylation of AKT at Thr308, calix[6]arene caused an increase in phosphorylation at Ser473. These findings in conjunction with increased BiP and IRE1-α provide a molecular basis explaining the capacity of calix[6]arene to trigger endoplasmic reticulum stress and autophagic cell death. Our findings highlight calix[6]arene as a potential candidate for overcoming pancreatic cancer aggressiveness. Importantly, we provide evidence that calix[6]arene affects a broad array of key targets that are usually dysfunctional in pancreatic cancer, a highly desirable characteristic for chemotherapeutics.

Ferruginol suppresses survival signaling pathways in androgen-independent human prostate cancer cells.

Ferruginol, a bioactive compound isolated from a Chilean tree (Podocarpaceae), attracts attention as a consequence of its pharmacological properties, which include anti-fungal, anti-bacterial, cardioprotective, anti-oxidative, anti-plasmodial and anti-ulcerogenic actions. Nevertheless, the molecular basis for these actions remains only partly understood and hence we investigated the effects of ferruginol on androgen-independent human prostate cancer cells (PC3), a known model for solid tumor cells with an exceptional resistance to therapy. The results show that ferruginol induces PC3 cell death via activation of caspases as well as apoptosis-inducing factor (AIF) as confirmed by its translocation into the nucleus. In order to clarify the biochemical mechanism responsible for the anti-tumor activity of ferruginol, we analyzed a set of molecular mediators involved in tumor cell survival, progression and aggressiveness. Ferruginol was able to trigger inhibition/downregulation of Ras/PI3K, STAT 3/5, protein tyrosine phosphatase and protein kinases related to cell cycle regulation. Importantly, the toxic effect of ferruginol was dramatically impeded in a more reducing environment, which indicates that at least in part, the anti-tumoral activity of ferruginol might be related to redox status modulation. This study supports further examination of ferruginol as a potential agent for both the prevention and treatment of prostate cancer.