Modulation of Caspase-Independent Cell Death Leads to Resensitization of Imatinib Mesylate–Resistant Cells

Abstract

Imatinib mesylate is widely used for the treatment of patients with chronic myelogenous leukemia (CML). This compound is very efficient in killing Bcr-Abl-positive cells in a caspasedependent manner. Nevertheless, several lines of evidence indicated that caspase-mediated cell death (i.e., apoptosis) is not the only type of death induced by imatinib. The goal of our study was to evaluate the importance of the newly described caspase-independent cell death (CID) in Bcr-Abl-positive cells. We established in several CML cell lines that imatinib, in conjunction with apoptosis, also induced CID. CID was shown to be as efficient as apoptosis in preventing CML cell proliferation and survival. We next investigated the potential implication of a recently identified mechanism used by cancer cells to escape CID through overexpression of the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH). We showed here, in several CML cell lines, that GAPDH overexpression was sufficient to induce protection from CID. Furthermore, imatinib-resistant Bcr-Abl-positive cell lines were found to spontaneously overexpress GAPDH. Finally, we showed that a GAPDH partial knockdown, using specific short hairpin RNAs, was sufficient to resensitize those resistant cells to imatinib-induced cell death. Taken together, our results indicate that CID is an important effector of imatinibmediated cell death. We also established that GAPDH overexpression can be found in imatinib-resistant Bcr-Ablpositive cells and that its down-regulation can resensitize those resistant cells to imatinib-induced death. Therefore, drugs able to modulate GAPDH administered together with imatinib could find some therapeutic benefits in CML patients. [Cancer Res 2009;69(7):3013-20]

GAPDH binds to active Akt, leading to Bcl-xL increase and escape from caspase-independent cell death

“…After treatment, cells were collected, washed in PBS and lysed as described previously. 21 When indicated, western blot quantification was performed using the multigauge software (Fujifilm).…”

“…20 In this direction, we previously established in the context of chronic myeloid leukemia (CML) that a spontaneous GAPDH overexpression was participating in the resistance of tumor cells to imatinibinduced death, thereby underlining the relevance of GAPDHdependent inhibition of CICD in pathological settings. 21 The phosphoinositide-3-kinase (PI3K) pathway is one of the most commonly altered signaling pathways in human cancers. 22 The best-characterized downstream effector is the Akt pathway, which is essential for cell survival and growth during development and carcinogenesis.…”

Combination of glycolysis inhibition with chemotherapy results in an antitumor immune response

“…29. Cell proliferation was measured using XTT (Roche), and the resulting data were used for quantitative diagnostic plots known as "isobolograms" as described in ref.…”

“…Western Blot Analysis. After treatment, cells were collected, washed, and lysed as described previously (29). Anti-Erk2, and -Hsp90 were purchased from Santa Cruz.…”

Glycolysis inhibition sensitizes tumor cells to death receptors-induced apoptosis by AMP kinase activation leading to Mcl-1 block in translation

“…Cell lysate and western blot analysis Briefly, after treatment, cells were collected, washed in phosphate-buffered saline and lysed as described previously (Lavallard et al, 2009). When indicated, western blot quantification was made using ImageJ software.…”