Abstract C147: Mechanism of resistance to a semisynthetic anticancer andrographolide derivative: Possible involvement of Ras-MAPK signaling pathway.

SRJ09 (3,19-(2-bromobenzylidene)andrographolide) has been identified as a lead anticancer agent on the basis of its selectivity towards breast and colon cancers in the USA NCI 60 cancer cell lines screen (Jada et al (2008) Br J Pharmacol, 155(5):641-54). In our recent seminal publication (Hocker et al (2013), PNAS, 110(25):10201-6), we revealed that the compound is a binder of oncogenic mutant K-Ras. In the present investigation, HCT116 colon cancer cells were made resistant to SRJ09 to elucidate the mechanism of resistance. MTT cell viability assay was utilized to screen for cross-resistance to other analogues of andrographolide (AGP) and standard anticancer drugs. Flow cytometry technique was utilized for cell cycle study. Western blot was performed to determine the expression of cell cycle, apoptosis regulatory and cell signaling proteins. Additionally, reverse transcriptase (RT)-PCR was carried out to determine the cell cycle regulatory genes. SRJ09-resistant HCT116 displayed approximately 40-fold resistance towards SRJ09 compared with the parental cells. However, the cells were not resistant towards AGP analogues and standard anticancer drugs. The cells failed to arrest in G1 phase upon treatment with SRJ09, unlike the parental cells. RT-PCR confirmed the findings that protein expression of p21 was not up-regulated and CDK4 was not down-regulated, contrary to the parental cells. The resistance of the cells to undergo apoptosis upon treatment with SRJ09 was mainly attributed to the unchanged levels of Bax, Bid, caspase 8 and 9, otherwise activated in the parental cells. The inability of the cells to experience cell cycle arrest and apoptosis might be attributed in part to the marginal changes in phosphorylated c-Raf and ERK1/2 protein levels, which are in complete contrast to the parental cells. In conclusion, the mechanism of resistance is very likely due to failure of c-Raf and ERK1/2 to undergo dephosphorylation, implicating Ras-MAPK pathway as a target of SRJ09. This study was funded by Universiti Putra Malaysia Research University Grant Scheme (04-01-09-0713RU; 04-02-12-2017RU).

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):C147.

Citation Format: Johnson Stanslas, Charng Choon Wong, Sreenivasa Rao Sagineedu, Shiran Sidik, Shariful Hasan Sumon, Roger Phillips, Nordin Haji Lajis. Mechanism of resistance to a semisynthetic anticancer andrographolide derivative: Possible involvement of Ras-MAPK signaling pathway. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr C147.