Phenyl 1,2,3-Triazole-Thymidine Ligands Stabilize G-Quadruplex DNA, Inhibit DNA Synthesis and Potentially Reduce Tumor Cell Proliferation over 3′-Azido Deoxythymidine

Abstract

Triazoles are known for their non-toxicity, higher stability and therapeutic activity. Few nucleoside (L1, L2 and L3) and non-nucleoside 1,2,3-triazoles (L4–L14) were synthesised using click chemistry and they were screened for tumor cell cytotoxicity and proliferation. Among these triazole ligands studied, nucleoside ligands exhibited higher potential than non-nucleoside ligands. The nucleoside triazole analogues, 3′-Phenyl-1,2,3- triazole-thymidine (L2) and 3′-4-Chlorophenyl-1,2,3-triazole-thymidine (L3), demonstrated higher cytotoxicity in tumor cells than in normal cells. The IC50 value for L3 was lowest (50 µM) among the ligands studied. L3 terminated cell cycle at S, G2/M phases and enhanced sub-G1 populations, manifesting induction of apoptosis in tumor cells. Confocal studies indicated that nucleoside triazole ligands (L2/L3) cause higher DNA fragmentation than other ligands. Preclinical experiments with tumor-induced mice showed greater reduction in tumor size with L3. In vitro DNA synthesis reaction with L3 exhibited higher DNA synthesis inhibition with quadruplex forming DNA (QF DNA) than non quadruplex forming DNA (NQF DNA). Tm of quadruplex DNA increased in the presence of L3, indicating its ability to enhance stability of quadruplex DNA at elevated temperature and the results indicate that it had higher affinity towards quadruplex DNA than the other forms of DNA (like dsDNA and ssDNA). From western blot experiment, it was noticed that telomerase expression levels in the tissues of tumor-induced mice were found to be reduced on L3 treatment. Microcalorimetry results emphasise that two nucleoside triazole ligands (L2/L3) interact with quadruplex DNA with significantly higher affinity (Kd≈10−7 M). Interestingly the addition of an electronegative moiety to the phenyl group of L2 enhanced its anti-proliferative activity. Though IC50 values are not significantly low with L3, the studies on series of synthetic 1,2,3-triazole ligands are useful for improving and building potential pro-apoptotic ligands.

Biological evaluation of 1,2,3‐triazole‐based polymers for potential applications as hard tissue material

“…4). The observed biocompatibility of the 1,2,3‐triazole‐based polymers P1–P8 is in accordance with literature data, stating a nontoxicity of many polytriazole‐containing structures, mainly designed in the pharmaceutical field, for example, as a tool for drug discovery for cancer treatment . Because of its chemical composition, the triazole units are not subject to metabolic degradation and are stable in typical biological conditions, which are usually of aqueous and mildly reducing nature .…”

G-quadruplexes: a promising target for cancer therapy

“…Binds preferentially to MYC G4 x [ 124 ] N,N'-bis(3,4-dihydroxbenzy lidene)-1,2-diaminobenzene (crosslinker) B16F1 m n.a. x [ 131 ] Naphthalene diimide derivatives (compound 2) SKMEL-5 h 48 h IC 50 : 1.7 μM x x [ 132 ] PhenDC3 A375 h 96 h GI 20 : 10 μM x [ 69 ] Phenyl 1,2,3-triazole-thymidine ligands (L1, L2, L3) B16F10 m 24 and 48 h IC 50 : 200 μM (L1), 125 μM (L2), 50 μM (L3) x [ 133 ] PPL3C M14 h 96 h IC 50 : 0.8 μM x [ 128 , 134 ] Pyridostatin A375 h 96 h GI 20 : 1.5 μM x [ 69 ] RHPS4 M14 h , PLF2 h , JR1 h , JR8 h , SBCL1 h , SAN h , LP h , LM h , JR5 h , M14 h 5 and 7 days IC 50 : 3.1 μM (5 days M14), ~1 μM (5 days PLF2 h , JR1, JR8, SBCL1, SAN) ~1 μM (7 days M14, PLF2 h , JR1, JR8, SBCL1, SAN) About 50% reduced tumor growth in melanoma xenografts x [ 135 – 137 ] ...…”

Synthesis, Cytostatic and Antibacterial Evaluations of Novel 1,2,3-Triazolyl-tagged Pyrimidine and Furo[2,3-d]pyrimidine Derivatives

“…6-Substituted furo [2,3-d]pyrimidine derivatives (7 and 8) were prepared by intramolecular in situ O-hereoannulation ring closure of N-1-alkyl-C-5-alkynylpyrimidine derivatives (3 and 5). Copper(I)-catalysed click reaction of 5-iodo-N-1-propargylpyrimidine (2) with corresponding azides followed by Sonogashira cross-coupling reaction with terminal alkynes gave novel 1,4-disubstituted 1,2,3-triazole tethered 5-alkynylpyrimidine (14-19) and 6-substituted furo [2,3-d]pyrimidines (20)(21)(22). In vitro antiproliferative activity of novel compounds evaluated on human cancer cell lines cervix adenocarcinoma (HeLa), colon adenocarcinoma (CaCo-2), chronic myeloid leukemia in blast crisis (K562), Burkitt lymphoma (Raji) revealed that 3,5-difluorophenyl and p-(trifluoromethyl)phenyl substituents in pyrimidine (19) and furo [2,3- …”

“…Introduction of alkynyl substituents at C-5 of pyrimidine ring by Sonogashira cross-coupling reaction of 9-13 gave 5-alkynylpyrimidines (14-19) and 6-substituted furo [2,3-d]pyrimidines (20)(21)(22) with 1,2,3-triazole moiety at N-1 and N-3, respectively. 6-Substituted furo [2,3-d]pyrimidines (20)(21)(22) were obtained by in situ 5-endo-dig cyclization of C-5-alkynyl-N-1-(1,2,3-triazolyl) uracil derivatives (16, 17 and 19) using CuI and base (Scheme 2).…”

“…[10][11][12][13][14][15] Thus, furo [2,3-d]pyrimidine attract considerable attention due to their great practical significance through exerting pharmacological potential as antiviral, antimicrobial, and antitumor agents, and is one of the most recently explored scaffolds to have potential anticancer activity through inhibition of various protein kinases. [16][17][18][19] Besides, it was found that some 1,2,3-triazole tethered pyrimidine nucleosides, [20] 1,2,3-triazole pyrimidine nucleoside conjugates with the 1,2,3-triazole as a substituent at the pyrimidine ring, [21] the sugar moiety [22] or sugar mimic [23] were endowed with a pronounced cytostatic activity. [24] In continuation of our efforts towards the hybridisation of pyrimidine and 1,2,3-triazole scaffolds into a single chemical entity, [25] we report here the synthesis and biological investigations of C-5 alkynylated pyrimidines and C-6-alkylated furo [2,3-d]pyrimidines containing N-1-substituted 1,2,3-triazole ring.…”