the difference between murine and human TB makes direct extrapolation of results

More interesting is the finding that AC Lapatinib overexpressing cells are more sensitive to Akt inhibition with regards to these functional assays than are controls cells. As AC resides in the lysosome, thus producing sphingosine primarily in this compartment, it may be that SphK1 has preferential or exclusive access to lysosomal sphingosine. We found that SphK2 KO MEFs had an increase in S1P equivalent to WT MEFs when we overexpressed AC, however SphK1 KO MEFs had no increase in S1P, consistent with this hypothesis. The observations in this study that AC promotes resistance to cytotoxic chemotherapies but sensitivity to agents that target Akt demonstrate important differences of the diverse functions mediated by AC. An exceedingly common and critical event in cell death in response to nonspecific stressors like radiation and chemotherapy is the accumulation of ceramide, which activates apoptosis through well characterized mechanisms. The efficacy of cytotoxic chemotherapies in this and previous studies have been shown to be lessened by expression of AC, presumably by Lymphatic system dampening the accumulation of ceramide and thus downstream apoptotic signals. In contrast, targeted inhibition of Akt proves especially effective in cells overexpressing AC, indicating that AC overexpressing cancer cells, and thus potentially AC overexpressing tumors, are reliant on oncogenic Akt activation through the pathway defined in this study for their oncogenic phenotypes. Chemotherapy for hormone refractory prostate cancer is currently limited to Docetaxel, which provides minimal benefit. Biopsy JZL184 based diagnostic methods could be readily adapted for evaluation of AC expression and Akt activation, potentially informing treatment decisions in the near future as PI3K and Akt inhibitors enter clinical use. Thus, while AC contributes to death resistance in the context of diverse cell stressors such as radiation and chemotherapy by attenuating ceramide accumulation, the identification in this study of AC mediated Akt activation provides critical insight into specific susceptibilities downstream of AC that could inform future clinical decisions. Akt signaling promotes proliferation indirectly by activating the mTOR pathway that controls translation of peptides necessary for cell growth, and directly by phosphorylating multiple cyclindependent kinase inhibitors. Our study of the functional consequences of AC induced Akt signaling reveals three important observations: AC expressing cells proliferate more rapidly, AC promotes soft agar colony formation and these oncogenic phenotypes are profoundly sensitive to Akt inhibition. That AC promotes cell proliferation is not surprising, given the signaling mechanism outlined in this study Akt phosphorylates Wee1 and Myt1 both of which promote mitotic entry by activating cdc2, and Akt directly inactivates the cyclin dependent kinase inhibitor p27kip1 whose inactivation allows transition from G1/S.