FLT3-ITD confers resistance to the PI3K/Akt pathway inhibitors by protecting the mTOR/4EBP1/Mcl-1 pathway through STAT5 activation in acute myeloid leukemia

Abstract

FLT3-ITD and FLT3-TKD are the most frequent tyrosine kinase mutations in acute myeloid leukemia (AML), with the former associated with poor prognosis. Here, we show that the PI3K inhibitor GDC-0941 or the Akt inhibitor MK-2206 induced apoptosis through the mitochondria-mediated intrinsic pathway more efficiently in hematopoietic 32D cells driven by FLT3-TKD (32D/TKD) than FLT3-ITD (32D/ITD), which robustly activated STAT5. The resistance to GDC-0941 and MK-2206 was gained by expression of the constitutively activated STAT5 mutant STAT5A1*6 in 32D/TKD cells, while it was abrogated by the STAT5 inhibitor pimozide in 32D/ITD cells or FLT3-ITD-expressing human leukemic MV4–11 cells. GDC-0941 or MK-2206 induced dephosphorylation of 4EBP1 more conspicuously in 32D/TKD than in 32D/ITD, which was prevented or augmented by STAT5A1*6 or pimozide, respectively, and correlated with downregulation of the eIF4E/eIF4G complex formation and Mcl-1 expression. Furthermore, exogenous expression of Mcl-1 endowed resistance to GDC-0941 and MK-2206 on 32D/TKD cells. Finally, it was confirmed in primary AML cells with FLT3-ITD that pimozide enhanced 4EBP1 dephosphorylation and Mcl-1 downregulation to augment cytotoxicity of GDC-0941. These data suggest that the robust STAT5 activation by FLT3-ITD protects cells treated with the PI3K/Akt pathway inhibitors from apoptosis by maintaining Mcl-1 expression through the mTORC1/4EBP1/eIF4E pathway.

Inhibition of cancer stem cells promoted by Pimozide

“…Additionally, Pimozide has showed an anticancer effect on other types of cancer: melanoma, CNS tumours, osteosarcoma, neuroblastoma, myeloproliferative neoplasms, breast, lung, prostate, ovarian, colorectal, pancreatic and hepatocellular carcinoma . Although, patients with mental disorders such as schizophrenia are less likely to develop cancer than the general population, there are yet no reports about the cancer incidence specifically in Pimozide users.…”

“…The DNA damage was measured by alkaline elution analysis, and cells treated with this combination were more affected than cells treated with Bleomicyn alone . Nogami et al administered 2 μmol/L of Pimozide in myeloid leukaemia and evaluated the numbers of viable cells after trypan blue staining. They verified that Pimozide only modestly reduced the viability of neoplastic cells, but combined treatment with GCD‐0941, a PI3K inhibitor, enhanced the results significantly …”

“…Nogami et al administered 2 μmol/L of Pimozide in myeloid leukaemia and evaluated the numbers of viable cells after trypan blue staining. They verified that Pimozide only modestly reduced the viability of neoplastic cells, but combined treatment with GCD‐0941, a PI3K inhibitor, enhanced the results significantly …”

“…Pimozide, an orally active antipsychotic agent used to treat Tourette's syndrome, chronic psychosis, resistant phonic, and motor tics, has been widely indicated as a potential anticancer agent . All studies that used Pimozide as an anti‐tumour drug showed positive results, mainly against CSC, which are responsible for chemoresistance …”

Interleukin-7 and -15 maintain pathogenic memory Th17 cells in autoimmunity

“…It has been reported that both Janus kinase 1/3–signal transducer and activator of transcription 5 (Jak1/3-STAT5) and phosphoinositide 3-kinase–Akt (PI3K-Akt) signaling pathways are involved in naïve and memory CD8 + T cell maintenance (21, 22–25). Thus, we cultured DED-pathogenic memory CD4 + T cells with: IL-7 and IL-15, IL-7 and anti-IL-15 Ab, IL-15 and anti-IL-7 Ab, IL-7, IL-15 and STAT5 inhibitor (pimozide) (26, 27), IL-7, IL-15 and Akt inhibitor (MK-2206) (27 – 29), IL-7, IL-15, STAT5 and Akt inhibitors. After 72 hours, we collected the cells and determined the frequencies of Th17 cells.…”