Discovery of potential targets of selenomethionine-mediated chemoprevention in colorectal carcinoma mouse model using proteomics analysis

Biomarker discovery by proteomics-based approaches for early detection and personalized medicine in colorectal cancer

About one million people per year develop colorectal cancer (CRC) and approximately half of them die. The extent of the disease (i.e. local invasion at the time of diagnosis) is a key prognostic factor. The 5-year survival rate is almost 90% in the case of delimited CRC and 10% in the case of metastasized CRC. Hence, one of the great challenges in the battle against CRC is to improve early diagnosis strategies. Large-scale proteomic approaches are widely used in cancer research to search for novel biomarkers. Such biomarkers can help in improving the accuracy of the diagnosis and in the optimization of personalized therapy. Herein, we provide an overview of studies published in the last 5 years on CRC that led to the identification of protein biomarkers suitable for clinical application by using proteomic approaches. We discussed these findings according to biomarker application, including also the role of protein phosphorylation and cancer stem cells in biomarker discovery. Our review provides a cross section of scientific approaches and can furnish suggestions for future experimental strategies to be used as reference by scientists, clinicians and researchers interested in proteomics for biomarker discovery.

Selenate specifically sensitizes drug-resistant cancer cells by increasing apoptosis via G2 phase cell cycle arrest without P-GP inhibition

The purpose of this study was to identify conditions that will increase the sensitivity of drug-resistant cancer cells. Selenium derivatives have been shown to present anti-cancer properties in the clinic. Currently, selenate, selenite, selenomethionine (SeMet), methyl-selenocysteine (MSC), and methaneselenic acid (MSA) are the most common selenium derivatives used as drugs in humans. Herein, we tested whether these selenium derivatives can sensitize KBV20C cancer cells, which are highly resistant to anti-cancer drugs such as vincristine. All five drugs could sensitize KBV20C cells to the same extent as they sensitized the sensitive parent KB cells, suggesting that selenium-derived drugs can be used for drug-resistant cancer cells. We also observed that these drugs did not inhibit the P-glycoprotein (P-gp) pumping-out ability, suggesting that the sensitization by selenium-derived drugs does not depend on P-gp activity in resistant KBV20C cells. Interestingly, using a cell viability assay, microscopic observation, and Hoechst staining, we found that selenate highly sensitized drug-resistant KBV20C cells by activating the apoptotic pathway, when compared to sensitive KB cells. Furthermore, we investigated why selenate sensitizes resistant KBV20C cells. Selenate-induced toxicity was associated with an increase in G2-phase cell cycle arrest in KBV20C cells, suggesting that the selenate-induced increase in apoptosis resulted from cell cycle arrest in resistant KBV20C cells. Our findings may contribute to the development of selenate-based therapies for patients resistant to cancer drugs.

Prohibitin 1 modulates mitochondrial function of Stat3

Mitochondrial dysfunction in intestinal epithelial cells (IEC) is thought to precede the onset of inflammatory bowel diseases (IBD). Expression of Prohibitin 1 (PHB), a mitochondrial protein required for optimal electron transport chain (ETC) activity, is decreased in mucosal biopsies during active and inactive IBD. In addition to its activities as a transcription factor, Signal Transducer and Activator of Transcription 3 (Stat3) resides in the mitochondria of cells where phosphorylation at S727 is required for optimal ETC activity and protects against stress-induced mitochondrial dysfunction. Here, we show that PHB overexpression protects against mitochondrial stress and apoptosis of cultured IECs induced by TNFα, which is a pro-inflammatory cytokine involved in IBD pathogenesis. Expression of pS727-Stat3 dominant negative eliminates protection by PHB against TNFα-induced mitochondrial stress and apoptosis. PHB interacts with pS727-Stat3 in the mitochondria of cultured IECs and in colonic epithelium from wild-type mice. Our data suggest a protective role of PHB that is dependent on pS727-Stat3 to prevent mitochondrial dysfunction in IECs. Reduced levels of PHB during IBD may be an underlying factor promoting mitochondrial dysfunction of the intestinal epithelium.