Perillyl alcohol selectively induces G0/G1 arrest and apoptosis in Bcr/Abl-transformed myeloid cell lines

Abstract

The Bcr/Abl tyrosine kinase that is expressed from the Philadelphia chromosome protects leukemia cells from apoptosis caused by removal of growth factors or by cytotoxic agents and ionizing irradiation. This resistance to apoptosis is associated with a Bcr/Abl-mediated G2/M delay. Therefore, inhibiting Bcr/Abl signaling pathways should block the ability of the Bcr/Abl kinase to protect cells from apoptosis. The monoterpenes, limonene and perillyl alcohol (POH) are new anticancer agents that selectively induce apoptosis in neoplastic cells of a variety of rodent carcinoma models. Since the potential antitumor activities of monoterpenes overlap with signaling pathways affected by the Bcr/Abl kinase, POH and limonene were tested for antileukemia activity. POH, but not limonene selectively induced G0/G1 arrest followed by apoptosis in Bcr/Abl-transformed, but not nontransformed FDC.P1 and 32D myeloid cell lines. In contrast to their greater sensitivity to POH, Bcr/Abl-transformed cells were more resistant than nontransformed cells to several chemotherapy agents and ionizing irradiation. Since in Bcr/Abl-transformed cells, POH induces apoptosis associated with G0/G1 arrest, POH must activate an apoptotic pathway that is not protected by the Bcr/Abl-induced G2/M delay. Monoterpenes may represent novel agents for treating Ph ؉ leukemias.

Antileukemia activity of perillyl alcohol (POH): uncoupling apoptosis from G0/G1 arrest suggests that the primary effect of POH on Bcr/Abl-transformed cells is to induce growth arrest

“…In contrast, in the presence of IL-3 or TPA, cells maintained equal viability at 12 h and demonstrated proliferation at 24 h. Combining IL-3 and TPA did not obviously alter the survival or proliferation of the cells. These, along with our earlier observations 51 suggest that there may be some overlap in the signaling pathways that can be affected by Bcr/Abl, IL-3 and TPA. Therefore, we reasoned that if POH blocks signals downstream from Bcr/Abl that confer resistance to apoptosis, 51 then TPA, which can protect cells from apoptosis following removal of growth factors, might also protect Bcr/Abl-transformed cells from POHinduced apoptosis.…”

“…51 Here, we further demonstrate that like Bcr/Abl and IL-3, the phorbol ester, TPA, also can protect the IL-3-dependent FDC.P1 ( Figure 1) and 32D (data not shown) hematopoietic cell lines from apoptosis caused by removal of growth factors. The data in Figure 1 show that the viability of FDC.P1 cells is severely reduced within 12 h, and that virtually all cells are dead 24 h after withdrawal from IL-3.…”

“…51 For control, nontransformed cell lines were infected with the retrovirus that only carried the tk-neo selectable marker and no Bcr/Abl. Infected cells were selected in G418 and multiple independently transformed clones were isolated.…”

“…We recently reported that POH, but not limonene, induced G1 arrest followed by apoptosis in Bcr/Abl-transformed cells. 51 Importantly, while Bcr/Abl-transformed hematopoietic cells are more resistant than nontransformed cells to cytotoxicity caused by various chemotherapy drugs and ionizing radiation, the Bcr/Abl transformants were more sensitive than their nontransformed counterparts to these effects of POH. Thus, the fact that in Bcr/Abl-transformed cells, POH induces apoptosis that is associated with a G1 arrest indicates that POH activates an apoptotic pathway that is not protected by the G2/M delay seen in the response of Bcr/Abl-transformed cells to other cytotoxic agents.…”

“…41 Monocyclic monoterpenes are produced in the mevalonate pathway of plants, but not mammalian cells, and represent a new class of anticancer compounds that can both prevent cancer and induce regression of advanced carcinomas in rats. Thus, dietary administration of the monoterpenes, limonene or perillyl alcohol (POH) can cure advanced mammary, stomach, lung, skin and liver cancers in rats, mice or hamsters [42][43][44][45][46][47][48][49][50][51] and they do not cause significant toxicity in rats, dogs or humans. [42][43][44][45][52][53][54][55][56] The anticancer activities of these monoter-penes are associated with a selective induction of apoptosis in the neoplastic tissue but not in adjacent normal tissues.…”