E6201 treatment resulted in a greater than 2 fold increase in Annexin positive staining in eleven out of fifteen cell lines, including eleven out of thirteen sensi tive cell lines. Two sensitive cell lines, SKMEL13 and BL, did not demonstrate selleckchem JQ1 E6201 induced Annexin staining although both of these cell lines underwent cell cycle arrest with E6201 treatment and were hypersensitive to E6201. These experiments Inhibitors,Modulators,Libraries were repeated in duplicate to confirm this finding. E6201 induced a less than two fold increase in Annexin staining in the E6201 insensitive cell lines. Three of the five PTEN mutant cell lines exhibited a cytocidal response to E6201, demonstrating that PTEN mutation does not pre clude a cytocidal response to E6201.

E6201 also induced cell cycle arrest and cell death in cell lines with constitutively active Akt, suggesting that although high pAkt correlates Inhibitors,Modulators,Libraries with E6201 insensitivity, cell lines with high pAkt can still undergo a cytocidal response to E6201. To confirm our Annexin V results we also performed an enzyme linked immunosorbent assay to de termine the degree of DNA fragmentation as an indica tor of cell death with E6201 treatment. The results from the cell death ELISA were very similar to that obtained from the Annexin studies with 10 out of 13 sensitive melanoma lines Inhibitors,Modulators,Libraries demonstrating a greater than two fold increase in DNA fragmentation with E6201. Of the three sensitive lines that did not exhibit a cytocidal response by ELISA, SKMEL13 and BL also demonstrated no induction of cell death with E6201 by Annexin positivity, as stated previously.

There was no significant induction of DNA fragmentation in any of the E6201 resistant melanoma cell lines. Characterization of E6201 response in vivo in melanoma xenografts We Inhibitors,Modulators,Libraries evaluated the in vivo activity of E6201 in two melan oma cell lines that exhibited a cytocidal response and two melanoma cell lines that exhibited a cytostatic response to E6201 in vitro. Given that the majority of sensitive melanoma cell lines in our cell line panel exhibited a cytocidal response to E6201 in vitro, we hypothesized that E6201 would induce tumour regression Inhibitors,Modulators,Libraries in a xeno graft model of these cell lines as well, and to a greater extent in those cell lines that demonstrated a cytocidal response to E6201 in vitro compared to those with a cytostatic response. Administration of E6201 at all doses to MM540 tumour bearing mice completely abrogated tumour growth and caused transient, Palbociclib Phase 3 partial tumour regression for the two weeks of drug treatment, although tumour growth recommenced following drug withdrawal, indicating not all cells were killed in this two week period.