Activated kRas protects colon cancer cells from cucurbitacin-induced apoptosis: the role of p53 and p21.
Cucurbitacins have been shown to inhibit proliferation in a variety of cancer cell lines. The aim of this study was to determine their biological activity in colon cancer cell lines that do not harbor activated STAT3, the key target of cucurbitacin. In order to establish the role of activated kRas in the responsiveness of cells to cucurbitacins, we performed experiments in isogenic colon cancer cell lines, HCT116 and Hke-3, which differ only by the presence of an activated kRas allele. We compared the activity of 23, 24-dihydrocucurbitacin B (DHCB) and cucurbitacin R (CCR), two cucurbitacins that we recently isolated, with cucurbitacin I (CCI), a cucurbitacin with established antitumorigenic activity. We showed that cucurbitacins induced dramatic changes in the cytoskeleton (collapse of actin and bundling of tubulin microfilaments), inhibited proliferation and finally induced apoptosis of both HCT116 and Hke-3 cells. However, the presence of oncogenic kRas significantly decreased the sensitivity of cells to the three cucurbitacins tested, CCR, DHCB and CCI. We confirmed that mutational activation of kRas protects cells from cucurbitacin-induced apoptosis using nontransformed intestinal epithelial cells with inducible expression of kRasV12. Cucurbitacins induced the expression of p53 and p21 predominantly in HCT116 cells that harbor mutant Ras. Using HCT116 cells with targeted deletion of p53 or p21 we confirmed that p53 and p21 protect cells from apoptosis induced by cucurbitacins. These results demonstrated that sensitivity of human colon cancer cell lines to cucurbitacins depends on the kRas and p53/p21 status, and established that cucurbitacins can exert antitumorigenic activity in the absence of activated STAT3.
Departament de Farmacologia, Facultat de Farmàcia, Universitat de València, Burjassot 46100, Spain.
José M
JM
Escandell
Pawan
P
Kaler
M Carmen
MC
Recio
Takehiko
T
Sasazuki
Senji
S
Shirasawa
Leonard
L
Augenlicht
José-Luis
JL
Ríos
Lidija
L
Klampfer
D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D003110:Colonic Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism; D006801:Humans; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D016283:Proto-Oncogene Proteins p21(ras); D014315:Triterpenes / Q000494:pharmacology*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D018631:ras Proteins / Q000378:metabolism*
D000970:Antineoplastic Agents; C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; C117307:KRAS protein, human; D011518:Proto-Oncogene Proteins; D014315:Triterpenes; D016159:Tumor Suppressor Protein p53; C517916:cucurbitacin R; D016283:Proto-Oncogene Proteins p21(ras); D018631:ras Proteins; C038106:cucurbitacin I; C478086:23,24-dihydrocucurbitacin B