Subsequent analysis of EGFR ex pression by flow cytometry and by western analysis for total and phospho EGFR showed selleck chem inhibitor significant variability between individual SCCHN cell lines, but no statistically sig selleck chemicals Trichostatin A nificant correlations with reovirus sensitivity. Indeed, if anything, there was a trend towards a negative correlation Inhibitors,Modulators,Libraries selleck chemicals llc between phospho EGFR on western analysis and reovirus sensitivity by IC50 estimation. Further studies in which we quantitated GTP loading on Ras and modulated signalling through Inhibitors,Modulators,Libraries the EGFR/Ras/MAPK Inhibitors,Modulators,Libraries axis failed to provide a clear indication of a cellular marker of sensitivity or resistance to reovirus. Indeed, it is interesting to note that the extent of in vitro reoviral replication did not correlate with cytotoxicity in Inhibitors,Modulators,Libraries SCCHN cells.

In this respect, the data are similar Inhibitors,Modulators,Libraries to those obtained in other studies using C26 colorectal tumour cells but, in direct contrast to those findings, the mechanism of death Inhibitors,Modulators,Libraries in SCCHN cells was non apoptotic. Therefore, despite clear evidence that there can be sig nificant variability in the susceptibility Inhibitors,Modulators,Libraries of SCCHN to reovirus Inhibitors,Modulators,Libraries induced cytotoxicity, detailed profil ing of pre and post entry events has failed to define a clear signaling biomarker of sensitivity or resistance. These findings have a number of implications. Most importantly, it is clear that, at least at the present time, an attempt to select SCCHN patients for oncolytic reovirus therapy on the basis of putative biomarkers in the EGFR/Ras/MAPK pathway is not a viable strategy.

In regard to the ongoing Inhibitors,Modulators,Libraries phase III study in patients with relapsed/metastatic Inhibitors,Modulators,Libraries head and neck cancers, Inhibitors,Modulators,Libraries our data provide reassurance that the eligibility criteria that allow entry of patients with platin refractory disease, irrespective Inhibitors,Modulators,Libraries of EGFR/Ras/MAPK pathway Inhibitors,Modulators,Libraries status, are appropriate. We cannot exclude the possibility that EGFR/Ras signaling may ultimately have some significant predictive value for reovirus therapy in SCCHN, especially in the light of the extensive intercon Inhibitors,Modulators,Libraries nectivity and redundancy of signaling pathways within tumour cells.

This would be consistent with findings in other oncolytic that systems in which early indications of specific genetic dependencies for oncolytic Inhibitors,Modulators,Libraries specificity turned out to be more complex than initially thought.

In addition, our studies here focus exclusively upon the genetic determinants of reovirus replication in tumour cells in culture. It is well established selleck bio that sensi tivity to viral replication and cytolysis in vitro can some times bear little relation to in vivo sensitivity of a tumour type, especially in the context of immunocompe tent models. We profiled innate immune response selleckbio in 4 repre sentative SCCHN cell lines and saw no clear correlation with reovirus sensitivity.