Sensitization of osteosarcoma cells to apoptosis by oncostatin M depends on STAT5 and p53

Abstract

Oncostatin M (OSM), a cytokine of the interleukin-6 family, induces growth arrest and differentiation of osteoblastic cells into glial-like/osteocytic cells. Here, we asked whether OSM regulates apoptosis of normal or transformed (osteosarcoma) osteoblasts. We show that OSM sensitizes cells to apoptosis induced by various death inducers such as staurosporine, ultraviolet or tumor necrosis factor-a. Apoptosis is mediated by the mitochondrial pathway, with release of cytochrome c from the mitochondria to the cytosol and activation of caspases-9 and -3. DNA micro-arrays revealed that OSM modulates the expression of Bax, Bad, Bnip3, Bcl-2 and Mcl-1. Pharmacological inhibitors, dominant-negative signal transducer and activator of transcriptions (STATs), stable RNA interference and knockout cells indicated that the transcription factors p53 and STAT5, which are activated by OSM, are implicated in the sensitization to apoptosis, being responsible for Bax induction and Bcl-2 reduction, respectively. These results indicate that, in addition to growth arrest and induced differentiation, OSM also sensitizes normal and transformed osteoblasts to apoptosis by a mechanism implicating (i) activation and nuclear translocation of STAT5 and p53 and (ii) an increased Bax/Bcl-2 ratio. Therefore, association of OSM with kinase inhibitors such as Sts represents new therapeutic opportunities for wild-type p53 osteosarcoma.

Allele-specific Col1a1 silencing reduces mutant collagen in fibroblasts from Brtl mouse, a model for classical osteogenesis imperfecta

“…26 The H1 promoter and the DNA cassette-coding shRNAs were then subcloned in pFG12, following a protocol previously described. 29 The resulting constructs were used to produce lentiviral particles. In all, 2-20 EGFP-viral units per cell were added to 3 Â 10 4 Brtl primary fibroblasts.…”

Signal Transducer and Activator of Transcription-5 Mediates Neuronal Apoptosis Induced by Inhibition of Rac GTPase Activity

“…However, critical studies in non-neuronal cells suggest that the downstream effects of STAT5 are much more complex. STAT5 sensitizes osteosarcoma cells to apoptosis following treatment with oncostatin M (32). Moreover, in a mouse model of familial amyotrophic lateral sclerosis, a JAK3 inhibitor was shown to extend the lifespan of mutant mice when compared with those that did not receive the inhibitor.…”

“…For example, STAT5 has been shown to negatively regulate the levels of Bcl-2 in osteosarcoma cells sensitized to undergo apoptosis (32). Similarly, both STAT5 isoforms were shown to bind to the promoter region of Bcl-x, a gene that is transcribed into prosurvival Bcl-xL and proapoptotic Bcl-extra short (Bcl-xS) (33,43,64).…”

“…Apoptosis-Recent studies suggest that under certain conditions STAT5 transcriptionally represses prosurvival members of the Bcl-2 family (32,33,43). Disturbances in the ratio of these proteins to their corresponding proapoptotic family members can induce apoptosis.…”

“…Roscovitine-Recent evidence demonstrates a necessary role for STAT5 in apoptosis induced by oncostatin M in osteosarcoma cells (32). In addition, both STAT5 isoforms have been implicated in the down-regulation of the prosurvival Bcl-xL protein in thymocytes (33).…”