Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ ALL) is triggered by constitutively activated BCR-ABL and SRC family tyrosine kinases.They account for the activations of multiple growth-signaling pathways, including Raf/MEK/ERK, Akt/mTOR and STAT5 pathways. The BCR-ABL tyrosine kinase inhibitor imatinib is the standard treatment for Ph+ leukemia and plays efficacious role in CML. However, imatinib has few inhibitory effects on SRC tyrosine kinase with response rate of Ph+ ALL lower and relapse more frequent and quicker compared with CML. Previous studies showed that oridonin inhibits proliferation and induces apoptosis in many tumor cells. However, the anticancer activity and mechanism of oridonin in Ph+ ALL is unknown. To investigate the anticancer activity of oridonin, we examined its role in constitutively activated Akt/mTOR, Raf/MEK/ERK, STAT5 and SRC pathway, mRNA level of bcr/abl gene, cell viability and apoptosis in Ph+ ALL SUP-B15 cells. Furthermore, we detected synergetic effect of oridonin plus imatinib. Our results showed that oridonin inhibiting activations of LYN (one of SRC family kinases) and ABL and their downstream Akt/mTOR, Raf/MEK/ERK and STAT5 pathways, downregulated Bcl-2 but upregulated Bax protein and then induced apoptosis in Ph+ ALL cells. Oridonin plus imatinib exerted synergetic effects by overcoming imatinib defect of upregulating Akt/mTOR and LYN signaling. Additionally, we examined the effect of oridonin on the signaling pathways in the primary specimens from Ph+ ALL patients. Our data showed that oridonin remarkably suppressed activations of Akt/mTOR, Raf/MEK and STAT5 pathway in these primary specimens and oridonin with imatinib exerted synergetic suppressive effects on mTOR, STAT5 and LYN signaling in one imatinib resistant patient specimen. Additional evaluation of oridonin as a potential therapeutic agent for Ph+ ALL seems warranted.

No abstract

The translocation (9;22) (q34;q11), known as the Philadelphia (Ph) chromosome and bcr-abl fusion gene, is the common cytogenetic abnormality and an unfavourable prognosis in adult acute lymphoblastic leukaemia (ALL). Although chemotherapeutic treatment produced high rates of complete response in approximately 70%-80% of newly diagnosed Ph+ ALL, the onset of resistance and clinical relapse is rapid. Therefore, the efficacy of treatment in Ph+ ALL is still to be determined. In this study, we aimed to assess the antileukemic activity of rapamycin (RAPA) (Sigma-Aldrich Corporation, MO, USA), a mammalian target of rapamycin inhibitor, alone and in combination with daunorubicin (DNR) (Pharmacia & Upjohn Company, Germany) in a Ph+ acute lymphoblastic cell line SUP-B15 and a primary Ph+ ALL sample in vitro. Here, we demonstrated that 50 nmol/L of RAPA significantly intensified the inhibition induced by DNR on both Ph+ ALL cell line and a primary Ph+ ALL sample. Notably, we reported that the consequence of DNR treatment induced the over expression of the components of mammalian target of rapamycin signalling pathway, whereas RAPA effectively eliminated this deleterious side effect of DNR, which might enhance DNR's ability to kill drug-resistant cancer. The synergistic effect was also associated with the increase in autophagy, blockage of cell cycle progression in the G1 phase. Altogether, our results suggest that DNR in combination with RAPA is more effective in the treatment of Ph+ ALL compared with DNR alone.