2009;30:1979C1986. providers, while ectopic manifestation of JAG2 improved chemoresistance of the CRC cells. Significant down-regulation of p21 was observed in JAG2-knockdown cells. Pressured manifestation of p21 rescued the level of sensitivity of JAG2-knockdown cells to doxorubicin. In addition, the chemosensitivity of p21-null cells was not affected by JAG2 knockdown. These results suggest that JAG2 modulates the level of sensitivity of CRC cells to chemotherapeutic providers through p21. Our study identifies JAG2 like a novel target for restorative treatment of CRC. part of JAG2 in CRC development using tissue-specific JAG2 knockout mice, since global deletion of JAG2 is definitely lethal . Our study also suggests that JAG1 and JAG2 may have unique tasks. Although their study demonstrated the part of JAG1 in CRC development, the part of JAG1 in chemoresistance has not been investigated. We have found that knockdown of JAG2, but not of JAG1, sensitized CRC cell lines to chemotherapeutic providers. This suggests that JAG2 may have its own signaling function that is important to cell survival 3CAI independent of the canonical NOTCH 3CAI pathway. On the other hand, it may be possible that JAG2 may have different receptor specificity than JAG1, or elicit different reactions when binding to the same NOTCH receptor. Supporting this idea, the mice that are null for the genes encoding JAG1, JAG2, or DLL4 show overlapping, but clearly unique phenotypes . Interactome analysis of JAG2 would reveal the mechanism underlying JAG2-mediated chemoresistance. We have identified p21 like a downstream effector involved in JAG2-rules of chemoresistance. JAG2 knockdown suppressed DOX-induced manifestation of p21, which is an inhibitor of DNA damage-induced apoptosis [42, 43], suggesting that reduced p21 level may be responsible for the improved level of sensitivity of JAG2 knockdown cells to DOX. In line with this, ectopic manifestation of p21 rescued the level of sensitivity of JAG2-knockdown cells to DOX. Moreover, the level of sensitivity of p21-null cells to DOX was not affected by JAG2 knockdown. JAG2 appears to regulate p21 mRNA levels since knockdown of JAG2 resulted in 50% decrease in p21 mRNA induction in response to DOX treatment. JAG2 knockdown also reduced the level of p21 in DOX-treated p53-null HCT116 cells, suggesting that JAG2 rules of p21 in these cells entails p53-independent mechanisms. It has been demonstrated that NOTCH positively regulates p21 manifestation in human being keratinocytes . Given that JAG2 is definitely a NOTCH ligand, it may be 3CAI possible that the reduced NOTCH activity due to JAG2 knockdown contributes to decreased levels of p21. However, additional mechanisms will also be possible. The silencing Rabbit Polyclonal to OR10AG1 of nuclear factor-B (NF-B) in p53-null HCT116 cells has been reported to enhance the cytotoxic effect of DOX through down-regulation of p21 . Consistent with this, NOTCH signaling offers been shown to induce IKK-mediated NF-B activation in human being keratinocytes . In addition, sphingosine kinase 2 (Sphk2) offers been shown to be involved in p53-self-employed induction of p21 in DOX-treated HCT116 cells . The level of p21 protein is also regulated by post-translational mechanisms including caspase-3-mediated cleavage  3CAI and proteasomal degradation . However, we have found that MG-132, a proteasome inhibitor, and Z-DEVD-FMK, a caspase-3 inhibitor, did not affect p21 levels in DOX-treated JAG2-knockdown cells (Supplementary Number 8 and data not demonstrated). We have made efforts to demonstrate the part of JAG2 under the stress of chemotherapeutic medicines which usually cause DNA damage as an end effect. DOX is definitely a potent DNA damaging drug and hence was utilized. 5-FU, oxaliplatin, and irinotecan are chemotherapeutic providers frequently used in individuals with CRC. Although we have demonstrated that JAG2 knockdown sensitized the CRC cells to 5-FU and oxaliplatin, one of the limitations in our study is the lack of evidence showing part of JAG2 in chemoresistance. Our future study will focus on the elucidation of part of JAG2 in CRC chemoresistance using tissue-specific JAG2 knockout animals. CRC is one of the leading causes of cancer-related deaths. The development of resistance to.