The present study has defined the need for additional exploration of the role of insulin and chemoresistance in colon cancer. However, going forward, a number of critical issues will need to be addressed if answers are to be found. These include: a) consideration of the insulin concentrations examined, typical molar concentrations for in vitro experimentation range between 15 and 40 nM, corresponding to the supra-physiological ranges depicted in Figure 1, rather than 1000 nM used in the current study; and b) the in vitro models employed, as chemoresistance in in vitro models generally take several weeks to develop. Other colon cancer lines and
chemotherapy Inhibitors,research,lifescience,medical agents need to be explored. Evaluating the effects of chronic insulin administration on the PI3K/Akt pathway does indeed seem to be a worthy pursuit. Inhibitors,research,lifescience,medical However, the cellular actions of insulin are likely to be pleotropic and the endpoints of the PI3K/Akt pathway extend beyond cell growth and apoptosis. Furthermore, small-molecule inhibitors used to assess the physiological roles of these enzymes should be cautiously interpreted, and specifically for PI3K inhibition, PI-103 is now the recommended in vitro tool, with superior Inhibitors,research,lifescience,medical specificity over LY294002 (as used in the present study), and rapamycin, a specific inhibitor
of TORC1, should be used in parallel to check whether any observed effects of PI-103 result from TORC1 inhibition (10). Finally, baseline mutational profiling of the cell lines of interest should be considered. Inhibitors,research,lifescience,medical HT29 cells are PI3K mutant, and as PIK3CA mutations lead to increased basal phosphatidylinositol-3-kinase activity, it is tempting to speculate that insulin signalling is constitutive in these cells. However, our laboratory has shown no distinguishing differences
in cell growth properties among cells carrying PIK3CA mutations from a panel of commonly Inhibitors,research,lifescience,medical used colon cancer cell lines under basal culture NVP-BGJ398 price conditions (11), but others have shown that mutational activation of the PI3K/Akt pathway may be essential for cellular growth under adverse however conditions, and for invasion (12). The paper of Chen and colleagues is timely, highlighting the many complexities and challenges facing investigators attempting to link clinical observations with biological mechanisms in the field of obesity and cancer. To better understand these complexities, there is a need for multi-disciplinary expertise to translate pre-clinical findings into meaningful clinical benefit for our patients with colorectal cancers. Footnotes AGR has served on the advisory board of and received research support from Novo Nordisk. CD has no potential conflict of interest.