In the analysis of the impact of the RB gene, the correlation with response to the Hec1 inhibitor TAI 1 was not estab lished in this database. However, when combined with the Hec1 expression level, the correlation with response to TAI 1 was more tight. When the two markers P53 and RB genes were com bined and correlated with the response to TAI 1, the correlation was also very strong. When combined with the Hec1 expression, the correlation was very tight. In vitro inhibition of RB and P53 and cellular sensitivity to TAI 1 To determine the role of RB and P53 in TAI 1 cellular sensitivity, in vitro siRNA knockdown assays were per formed in cells carrying wild type RB and P53, respect ively. HeLa, which carry mutated RB and mutated P53, was used as the control cell line during the knockdown assays.

To determine the role of RB in TAI 1 cellular sensitiv ity, siRNA to RB was used in cell lines carrying wild type RB, including MDA MB 231, K562, ZR 75 1, T47D, A549, and HCT116. After siRNA treatment, cells were treated with TAI 1 and analyzed at 48 hours after TAI 1 treatment with MTS assay. In the first experiment, a full scale GI50 was assessed in MDA MB 231 kinase inhibitor cells following siRNA transfection. A 20% decrease in RB RNA levels was seen in conjunction with a 7% decrease of GI50 in. In subsequent experiments with other cell lines, single dose inhibition was assessed. Using the protocol described in the Methods section, we were able to show the decreased RB protein and this was associated with a 10 25% enhancement in cancer cell proliferation inhibition.

In experiments with HeLa as a control, siRNA incubation showed a reduction in the expression of the mutant RB but no effect on the cellular sensitivity to TAI 1. To ensure that this effect was not RB siRNA sequence specific, knockdown with a different RB siRNA sequence was conducted which showed similar results. Knockdown of RB in selleck chemicals SB-480848 wild type RB cancer cells lead to increased sensitivity to TAI 1. To determine the role of P53 in TAI 1 cellular sensitivity, siRNA to P53 was used in cell lines carrying wild type P53, including A549, HCT116, ZR 75 1, and U2OS, were used for P53 knockdown assays. The same methods as RB study were used. As shown in Figure 8A, a 60 80% decrease in P53 RNA levels lead to 30 50% decrease of GI50 in A549 and HCT116 cells, and this was associated with a 10 20% increase in the enhancement of cancer cell proliferation in hibition.

Again, in HeLa cells, which has a mutant P53 and served as a control, siRNA also inhibit the expression of mutant P53 RNA but had no effect on the cellular proliferation inhibition activity of TAI 1. Fur thermore, to ensure that the effect is not siRNA sequence specific, knockdown with a different P53 siRNA sequence was conducted and showed similar results.