Apoptosis and autophagic cell deaths are programmed cell deaths and they play essential roles in cell survival, growth and development and tumorigenesis. The huge increase of publications in both apoptosis and autophagic signaling pathways has contributed to the wealth of knowledge in facilitating the understanding of cancer pathogenesis. Deciphering the molecular pathways and molecules involved in these pathways has helped scientists devise and develop targeted strategies against cancer. Various drugs targeting the apoptotic TRAIL, Bcl-2 and proteasome pathways are already in Phase II/III clinical trials. The first mTOR inhibitor, temsirolimus has already been approved by the FDA, USA for the treatment of advanced renal cell carcinoma and more mTOR inhibitors are expected to be in the market in a few years time. Strategizing against aberrant autophagy activities in various cancers by using either pro-autophagics or autophagy inhibitors are currently been investigated. This review aims to discuss the most recent antitumor strategies targeting the apoptosis and autophagy signaling pathways and the latest outcome of clinical trials of the above drugs.

The mammalian target of rapamycin (mTOR) kinase plays an important role in regulating cell growth and cell cycle progression in response to cellular signals. It is a key regulator of cell proliferation and many upstream activators and downstream effectors of mTOR are known to be deregulated in various types of cancers. Since the mTOR signalling pathway is commonly activated in human cancers, many researchers are actively developing inhibitors that target key components in the pathway and some of these drugs are already on the market. Numerous preclinical investigations have also suggested that some herbs and natural phytochemicals, such as curcumin, resveratrol, timosaponin III, gallic acid, diosgenin, pomegranate, epigallocatechin gallate (EGCC), genistein and 3,3'-diindolylmethane inhibit the mTOR pathway either directly or indirectly. Some of these natural compounds are also in the clinical trial stage. In this review, the potential anti-cancer and chemopreventive activities and the current status of clinical trials of these phytochemicals are discussed.

Autophagy is an evolutionarily conserved lysosomal degradation pathway and plays a critical role in the homeostatic process of recycling proteins and organelles. Functional relationships have been described between apoptosis and autophagy. Perturbations in the apoptotic machinery have been reported to induce autophagic cell deaths. Inhibition of autophagy in cancer cells has resulted in cell deaths that manifested hallmarks of apoptosis. However, the molecular relationships and the circumstances of which molecular pathways dictate the choice between apoptosis and autophagy are currently unknown. This study aims to identify specific gene expression of rapamycin-induced autophagy and the effects of rapamycin when the autophagy process is inhibited. In this study, we have demonstrated that rapamycin is capable of inducing autophagy in T-47D breast carcinoma cells. However, when the autophagy process was inhibited by 3-MA, the effects of rapamycin became apoptotic. The Phlda1 gene was found to be up-regulated in both autophagy and apoptosis and silencing this gene was found to reduce both activities, strongly suggests that Phlda1 mediates and positively regulates both autophagy and apoptosis pathways.

The tumor suppressor gene p15(INK4b) is a cyclin-dependent kinase inhibitor, in which its inactivation has been determined in primary tumors and in several tumor-derived cell lines. The precise role of p15(INK4b) protein expression in cutaneous squamous cell carcinoma (SCC) is currently not known. In a previous study, we have shown the frequent occurrence of allelic imbalance/loss of heterozygosity in cutaneous SCC using two microsatellite markers flanking the p15(INK4b) gene. This study is a continuation of our previous study and aims to determine the possible role of p15(INK4b) protein expression in the genesis of cutaneous SCC. P15(INK4b) protein expression was determined using immunohistochemical approach in 107 cases of cutaneous SCC tissue arrays and 19 cases of normal human skin tissues. The expression of p15(INK4b) was significantly reduced in the cutaneous SCC cases as compared with normal human skin (p = 0.017 and p < 0.05). However, there were no significant relationship between clinicopathologic variables of the patients (age, sex and tumor grade) and p15(INK4b) protein expression. The absence of p15(INK4b) expression in the majority of tissue microarray cores of cutaneous SCC indicated that p15(INK4b) could possibly be involved in the pathogenesis of cutaneous SCC.

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