Antileukemic Activity of Lysophosphatidic Acid Acyltransferase-beta Inhibitor CT32228 in Chronic Myelogenous Leukemia Sensitive and Resistant to Imatinib

Purpose: Lysophosphatidic acid acyltransferase (LPAAT)-beta catalyzes the conversion of lysophosphatidic acid to phosphatidic acid, an essential component of several signaling pathways, including the Ras/mitogen-activated protein kinase pathway. Inhibition of LPAAT-beta induces growth arrest and apoptosis in cancer cell lines, implicating LPAAT-beta as a potential drug target in neoplasia.

Experimental Design: In this study, we investigated the effects of CT32228, a specific LPAAT-beta inhibitor, on BCR-ABL-transformed cell lines and primary cells from patients with chronic myelogenous leukemia.

Results: CT32228 had antiproliferative activity against BCR-ABL-positive cell lines in the nanomolar dose range, evidenced by cell cycle arrest in G2-M and induction of apoptosis. Treatment of K562 cells with CT32228 led to inhibition of extracellular signal-regulated kinase 1/2 phosphorylation, consistent with inhibition of mitogen-activated protein kinase signaling. Importantly, CT32228 was highly active in cell lines resistant to the Bcr-Abl kinase inhibitor imatinib. Combination of CT32228 with imatinib produced additive inhibition of proliferation in cell lines with residual sensitivity toward imatinib. In short-term cultures in the absence of growth factors, CT32228 preferentially inhibited the growth of granulocyte-macrophage colony-forming units from chronic myelogenous leukemia patients compared with healthy controls.

Conclusion: These data establish LPAAT-beta as a potential drug target for the treatment of BCR-ABL-positive leukemias.