Pivotal role of dihydrofolate reductase knockdown in the anticancer activity of 2-hydroxyoleic acid

Abstract

␣-Hydroxy-9-cis-octadecenoic acid, a synthetic fatty acid that modifies the composition and structure of lipid membranes. 2-Hydroxyoleic acid (HOA) generated interest due to its potent, yet nontoxic, anticancer activity. It induces cell cycle arrest in human lung cancer (A549) cells and apoptosis in human leukemia (Jurkat) cells. These two pathways may explain how HOA induces regression of a variety of cancers. We showed that HOA repressed the expression of dihydrofolate reductase (DHFR), the enzyme responsible for tetrahydrofolate (THF) synthesis. Folinic acid, which readily produces THF without the participation of DHFR, reverses the antitumor effects of HOA in A549 and Jurkat cells, as well as the inhibitory influence on cyclin D and cdk2 in A549 cells, and on DNA and PARP degradation in Jurkat cells. This effect was very specific, because either elaidic acid (an analog of HOA) or other lipids, failed to alter A549 or Jurkat cell growth. THF is a cofactor necessary for DNA synthesis. Thus, impairment of DNA synthesis appears to be a common mechanism involved in the different responses elicited by cancer cells following treatment with HOA, namely cell cycle arrest or apoptosis. Compared with other antifolates, such as methotrexate, HOA did not directly inhibit DHFR but rather, it repressed its expression, a mode of action that offers certain therapeutic advantages. These results not only demonstrate the effect of a fatty acid on the expression of DHFR, but also emphasize the potential of HOA to be used as a wide-spectrum drug against cancer.anticancer ͉ DNA ͉ membrane-lipid therapy ͉ neoplasia ͉ nutrigenetics 2 -Hydroxyoleic acid (HOA) is a potent anticancer drug whose molecular mechanism of action is still not fully understood. Although HOA induces cell cycle exit in human lung cancer (A549) cells (1), it induces apoptosis in human leukemia cells (2). The IC 50 of this drug for most cancer cells studied is in the range of 30-150 M, whereas its IC 50 in normal cells is over 5,000 M (2). Thus, this drug does not produce toxicity at therapeutic doses despite acting efficiently in cell and animal models of human cancers (2, 3). Hence, it is important to define the mode of action of this compound and whether common molecular events underlie its therapeutic effects and the regression of different types of cancer.HOA was developed on the basis that the lipid composition and structure of the plasma membrane can be altered by certain antitumor drugs and that these modifications are involved in their action against cancer (4, 5). In this context, anthracyclines that are unable to enter cancer cells or bind to DNA still have strong antitumor activity (6). Indeed, those used in human therapy regulate plasma membrane structure, and they induce changes in the localization and activity of important peripheral signaling proteins, such as G proteins and PKC (4,7,8). This mode of action also appears to be responsible for the activity of hexamethylene bisacetamide against cancers (9, 10).In the search for molecules capable of i...

Sphingomyelin and sphingomyelin synthase (SMS) in the malignant transformation of glioma cells and in 2-hydroxyoleic acid therapy

“…1B). These results extend previous studies, showing that 2OHOA has a distinct effect on DHFR in tumor and nontumor cells (1,3,4).…”

“…Nevertheless, the regulatory effects of 2OHOA on the composition of cancer cell membranes have yet to be described. In fact, 2OHOA induces changes in the localization and activity of membrane proteins involved in cancer cell proliferation, differentiation and survival, such as the Fas receptor (4), PKC (3), as well as cyclins, cyclin-dependent kinases (CDKs), caspases, E2F-1 and dihydrofolate reductase (DHFR) (1,2). Interestingly, a similar mechanism is described for edelfosine, a synthetic ether lipid with a high apoptotic activity that also induces reorganization of membrane rafts, FasR capping, and cell apoptosis (7).…”

2-Hydroxyoleate, a nontoxic membrane binding anticancer drug, induces glioma cell differentiation and autophagy

“…S2) that already exhibit high basal levels of SM. The increase in DAG and the presence of 2OHOA itself favors the cytosol to membrane translocation and activation of PKCα (4,10) that is associated with knockdown of E2F-1 and DHFR (5,6). The increase in membrane 2OHOA was likely associated with short-term (10 min) Ras release from the membrane and the subsequent inhibition of the ERK pathway, and changes in SM and PE could be related the long-term Ras translocation ( Fig.…”

“…On the one hand, the presence of 2OHOA in membranes and the increase in DAG would induce PKC translocation to membranes followed by CDKI overexpression and pRb hypophosphorylation (this work and refs. [4][5][6]. On the other hand, Ras translocation to the cytosol would cause MAPK and Akt inactivation.…”

“…This efficacy and lack of toxicity at therapeutic doses has been acknowledged recently by the European Medicines Agency (EMA) to designate 2OHOA orphan drug for the treatment of glioma. In previous studies, we showed that this compound induces cell cycle arrest of lung cancer cells (4)(5)(6). Here, we showed that 2OHOA reversed the altered lipid profile of glioma cells and how this modification regulated cell signaling to induce autophagy specifically in glioma but not normal cells.…”