Antiproliferative Effect of N-Heterocyclo-Coumarin Derivatives against Multidrug-Resistant Cells

Chemotherapy refers principally to the use of small molecules to treat cancer, and natural product derivatives have been main sources of clinically using anticancer drugs. While the coumarin skeleton does not inhibit cell growth, its derivatives are often active, and numerous coumarins have been examined for antiproliferative activity against human cancer cell lines. In this study, 16 novel coumarin derivatives (1, 1a-5a, 1b, 2b, 6b, 7b, 8-13) with attached N-heterocycles, including aminopyrrolidine, aminopiperidine, aminoazepane, and indoline, were prepared and ultimately esterified or amidated with alcohols or amines, respectively. All synthesized N-heterocycles containing coumarin derivatives with alcohols, amines, and carboxylic acids were assessed for antiproliferative activity against several human cancer cell lines, containing triple-negative breast cancer (TNBC) as well as a P-glycoprotein (P-gp) overexpressing multidrug-resistant (MDR) KB subline KB-VIN. Five coumarin derivatives (3a-5a, 12, 13) showed no effect (IC₅₀ >40 µM) against all tested cell lines. In contrast, derivative 1a showed broad-spectrum activity against four cell lines, while 1b and 10 were nearly twice as selective for KB-VIN cells as the parent KB. The coumarin derivatives 1a, 1b, and 10 were optimal for antiproliferative activity in this study and could provide a new avenue for overcoming MDR tumors. Derivatives 1a, 1b, and 10 showed MDR cell-selective antiproliferative activity, indicating that N-heterocycle-coumarins exert previously unexplored bioactivity with selective action on MDR cancer cells.

Safe and targeted anticancer efficacy of a novel class of antioxidant-conjugated difluorodiarylidenyl piperidones: differential cytotoxicity in healthy and cancer cells

The development of smart anticancer drugs that can selectively kill cancer cells while sparing the surrounding healthy tissues/cells is of paramount importance for safe and effective cancer therapy. We report a novel class of bifunctional compounds based on diarylidenyl piperidone (DAP) conjugated to an N-hydroxypyrroline (NOH; a nitroxide precursor) group. We hypothesized that the DAP would have cytotoxic (anticancer) activity, whereas the NOH moiety would function as a tissue-specific modulator (antioxidant) of cytotoxicity. The study used four DAPs, namely H-4073 and H-4318 without NOH and HO-3867 and HO-4200 with NOH substitution. The goal of the study was to evaluate the proof-of-concept anticancer-versus-antioxidant efficacy of the DAPs using a number of cancerous (breast, colon, head and neck, liver, lung, ovarian, and prostate cancer) and noncancerous (smooth muscle, aortic endothelial, and ovarian surface epithelial) human cell lines. Cytotoxicity was determined using an MTT-based cell viability assay. All four compounds induced significant loss of cell viability in cancer cells, whereas HO-3867 and HO-4200 showed significantly less cytotoxicity in noncancerous cells. EPR measurements showed a metabolic conversion of the N-hydroxylamine function to nitroxide with significantly higher levels of the metabolite and superoxide radical-scavenging (antioxidant) activity in noncancerous cells compared to cancer cells. Western blot analysis showed that the DAP-induced growth arrest and apoptosis in cancer cells were mediated by inhibition of STAT3 phosphorylation at the Tyr705 and Ser727 residues and induction of apoptotic markers of cleaved caspase-3 and PARP. The results suggest that the antioxidant-conjugated DAPs will be useful as safe and effective anticancer agents for cancer therapy.

Influence on antiproliferative activity of structural modification and conjugation of gonadotropin-releasing hormone (GnRH) analogues

The effect of various GnRH analogues, and their conjugates on proliferation, clonogenicity and cell cycle phase distribution of MCF-7 and Ishikawa human cancer cell lines was studied. GnRH-III, a sea lamprey GnRH analogue reduced cell proliferation by 35% and clonogenicity by 55%. Structural modifications either decreased, or did not alter biological activity. Conjugation of GnRH analogues including MI-1544, MI-1892, and GnRH-III with poly(N-vinylpyrrolidone-co-maleic acid) (P) through a tetrapeptide spacer GFLG(X) substantially increased the inhibitory effect of the GnRH analogues. The conjugate P-X-GnRH-III induced significant accumulation of cells in the G2/M phase; from 8% to 15.6% at 24 h and 9.8% to 15% at 48 h. It was concluded that conjugation of various GnRH analogues substantially enhanced their antiproliferative activity, strongly reduced cell clonogenicity and retarded cell progression through the cell division cycle at the G2/M phase.