Novel Amphiphilic G-Quadruplex Binding Synthetic Derivative of TMPyP4 and Its Effect on Cancer Cell Proliferation and Apoptosis Induction

Porphyrins are well-known anticancer agents because of their high binding affinity for G-quadruplex DNA and excellent photophysical properties. Several studies carried out using TMPyP4 established it as an efficient chemotherapeutic and a photodynamic therapeutic (PDT) agent, but its use as a lead molecule has been restricted because of its high level of binding to double-stranded DNA (dsDNA), which may have side effects on normal cells and tissues. To minimize its interaction with dsDNA and to enhance internalization into cells, an analogue of TMPyP4 (SMe) was synthesized. Its selectivity for G-quadruplex DNA over dsDNA was evaluated by spectroscopic methods, and its role in stabilizing G-quadruplex DNA was assessed by fluorescence lifetime and thermal melting experiments. Biophysical studies indicated that SMe interacts well with G-quadruplex DNA. In vitro cytotoxicity experiments with tumor cell lines (PANG-1, B16F10, and MDA MB 231) have revealed that SMe can inhibit the growth of cancer cells comparable to TMPyP4. MTT and apoptotic assays demonstrated the ability of SMe to specifically affect cancer cells over normal cells. Cell cycle analysis showed that SMe, like TMPyP4, induces G2/M phase cell cycle arrest. In addition, SMe is more effectively taken up by both cancer and normal cells than TMPyP4. In addition, we have noticed that SMe is more efficient than TMPyP4 in inhibiting the growth of the cancer cells after irradiation with light (600-720 nm, 20 J/cm(2), 50 mW/ cm(2)). By and large, these experimental results indicate that SMe can be an efficient chemotherapeutic as well as a PDT agent.