Targeting melanoma growth and viability reveals dualistic functionality of the phosphonothionate analogue of carba cyclic phosphatidic acid

Abstract

BackgroundAlthough the incidence of melanoma in the U.S. is rising faster than any other cancer, the FDA-approved chemotherapies lack efficacy for advanced disease, which results in poor overall survival. Lysophosphatidic acid (LPA), autotaxin (ATX), the enzyme that produces LPA, and the LPA receptors represent an emerging group of therapeutic targets in cancer, although it is not known which of these is most effective.ResultsHerein we demonstrate that thio-ccPA 18:1, a stabilized phosphonothionate analogue of carba cyclic phosphatidic acid, ATX inhibitor and LPA1/3 receptor antagonist, induced a marked reduction in the viability of B16F10 metastatic melanoma cells compared with PBS-treated control by 80-100%. Exogenous LPA 18:1 or D-sn-1-O-oleoyl-2-O-methylglyceryl-3-phosphothioate did not reverse the effect of thio-ccPA 18:1. The reduction in viability mediated by thio-ccPA 18:1 was also observed in A375 and MeWo melanoma cell lines, suggesting that the effects are generalizable. Interestingly, siRNA to LPA3 (siLPA3) but not other LPA receptors recapitulated the effects of thio-ccPA 18:1 on viability, suggesting that inhibition of the LPA3 receptor is an important dualistic function of the compound. In addition, siLPA3 reduced proliferation, plasma membrane integrity and altered morphology of A375 cells. Another experimental compound designed to antagonize the LPA1/3 receptors significantly reduced viability in MeWo cells, which predominantly express the LPA3 receptor.ConclusionsThus the ability of thio-ccPA 18:1 to inhibit the LPA3 receptor and ATX are key to its molecular mechanism, particularly in melanoma cells that predominantly express the LPA3 receptor. These observations necessitate further exploration and exploitation of these targets in melanoma.

MicroRNA-30c-2* Expressed in Ovarian Cancer Cells Suppresses Growth Factor–Induced Cellular Proliferation and Downregulates the Oncogene BCL9

“…OVCAR-3, SKOV-3, or HeyA8 cells were examined for viability as previously described (14,20) using CellTiter Blue reagent (Promega). In cisplatin and paclitaxel treatment experiments, the cells were treated with chemotherapy after 24 hours of transfection.…”

“…siRNA knockdown of LPA receptors SKOV-3 cells were transfected with Dharmacon SMART pools of siRNA reagents (ThermoScientific/Dharmacon, Inc.) targeting the individual LPA receptors as previously described (14) using Dharmafect reagent (ThermoScientific/Dharmacon) and following the protocol provided by the manufacturer.…”

“…Moreover, miRNAs are frequently deregulated in ovarian cancer and because LPA enhances tumorigenicity in this malignancy (10), we also questioned whether LPA elicited a specific miRNA response that is either reduced or eliminated during tumorigenesis, contributing to ovarian malignancy. Because LPA potently induces cell growth, proliferation, viability, and survival (13)(14)(15)(16), this effect would most likely be observed through precursor miRNA counter induction to reduce these specific cellular processes.…”

A Bromophosphonate Analogue of Lysophosphatidic Acid Surpasses Dacarbazine in Reducing Cell Proliferation and Viability of MeWo Melanoma Cells

“…This enzyme, autotaxin (ATX), was first isolated from the conditioned medium of melanoma cells and was thought to be responsible for melanoma cell motility (Stracke, Krutzsch et al 1992). Recent studies have shown that targeting either the LPA3 receptor or ATX effectively reduces melanoma cell viability (Altman et al 2010). Furthermore, research devoted to producing inhibitors and antagonists targeting the ATX-LPA receptor axis has yielded a large variety of compounds (Albers, Dong et al 2010;Altman et al 2010;Baker, Fujiwara et al 2006;Block, Duff et al 2010;Hoeglund, Bostic et al 2010;North, Howard et al 2010;Xu, Yang et al 2009), suggesting the critical role of this pathway in cancer.…”

“…Interestingly, the lysophospholipase D that is responsible for the vas t m a j o r i t y o f t h e production of LPA from lysophosphatidylcholine is also expressed extracellularly and is a major target in melanoma (Altman et al 2010;Liu, Murph et al 2009). This enzyme, autotaxin (ATX), was first isolated from the conditioned medium of melanoma cells and was thought to be responsible for melanoma cell motility (Stracke, Krutzsch et al 1992).…”