Abstract 3664: Hybrid anticancer drugs: Synthesis of a combretastatin-piperlongumine analog with mutant p53 reactivation and antimicrotubule properties
Authors: Punganuru Surendra R. , Madala Hanumantharao , Srivenugopal Kalkunte S. 
Published: August 2015

The axiomatic tumor heterogeneity of human cancers and their resistance to current anticancer drugs has necessitated that we develop innovative treatment strategies. In this regard, combined drugs that impact two or more targets simultaneously are likely to offer superior chemosensitivity. Here, we describe the design and development of a compound with ROS-generating and microtubule-disrupting properties. Combretastatins (CA4) are small molecule cytotoxic agents of natural origin, known to disrupt microtubule dynamics by binding to the colchicine site and also inhibit angiogenesis. Despite the potent anticancer activity of CA4, the cis-configured double bond in its structure is prone for isomerization to the more stable trans form during storage and metabolism, resulting in loss of activity. In contrast, piperlongumine (PL), which has structural similarities with CA4, is known to selectively increase ROS levels and induce apoptosis in cancer cells. Here, we present the synthesis and biological evaluation of combretastatin-piperlongumine hybrid derivatives that inhibit tubulin polymerization, reactivate mutant p53 and induce oxidative stress in cancer cell lines. These CA4-PL hybrid derivatives were prepared by introducing the aryl group at the C7-carbon of piperlongumine in such a way that carbonyl group at C6 position will stabilize the cis-configuration between two aryl groups which is essential for the microtubule destabilization. The new compounds exhibited potent antiproliferative activities against a variety of cancer cell lines, particularly against cells with the DNA-contact p53 mutations, R175H (SKBR-3) and R273H (HT29). Cell cycle analysis revealed that CA4-PL analogs exhibited significant G2/M arrest and in vitro-tubulin polymerization assays confirmed the microtubule destabilizing actions. Immunocytochemistry revealed a loss of intact microtubule structure in cells treated with CA4-PL hybrid compounds, indicating the acquisition of combretastatin nucleus. Further, the compounds induced high levels of ROS selectively in cancer cells as determined by flow cytometry assays using DCF-DA. Most interestingly, the hybrid drugs showed the ability to reactivate the p53 mutations R273H and R175H- a progressive decline of mutant forms along with a gradual increase of wt p53 was evident from immunological assays using specific antibodies (Mabs 240 & 1620 respectively) and EMSAs. p53 reactivation was accompanied by the induction of the target genes, p21cip1 and Bax. We hypothesize that redox-perturbation induced by the hybrid drugs triggers the thiolation of specific redox-sensitive cysteines to cause p53 reactivation. Xenograft studies to test these observations in vivo are in progress. We believe such rationally designed compounds with dual actions hold much promise for drug development (supported by CPRIT grant RP130266 to KSS).

Citation Format: Surendra R. Punganuru, Hanumantharao Madala, Kalkunte S. Srivenugopal. Hybrid anticancer drugs: Synthesis of a combretastatin-piperlongumine analog with mutant p53 reactivation and antimicrotubule properties. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3664. doi:10.1158/1538-7445.AM2015-3664