TITLE & ABSTRACT of talk - Prof Mala Nath
*Author for correspondence. E-mail: firstname.lastname@example.org
Department of Chemistry, Indian Institute of Technology Roorkee, Roorkee-247667, India
Developments in Organotin-based Anti-cancer Compounds
Enormous advances have been made in the field of cancer chemotherapy during the past fifty years. Prior to 1969, however, arsenal of chemotherapeutic agents was devoid of compounds which are inorganic in nature because of generally accepted belief that most metals and their compounds were potentially carcinogenic. Cis-platin is the first drug from Inorganic chemistry to have come under routine clinical use in medical oncology (in 1986, it was the largest selling anticancer drug worldwide), and its success placed the co-ordination chemists on the front line in the fight against cancer. Naturally, this discovery also stimulated the search for other metal-containing compounds with potential anticancer activity. Although the majority of these successes involved complexes containing transition metal ions, but some main group metal (viz. Al, Ga, In, Tl; Ge, Sn, Pb; Bi) compounds, especially organotins, have also been discovered which show promise as future members of man’s anticancer arsenal. The National Cancer Institute (NCI) has tested about 2000 tin-based compounds, the largest number ever tested among metal complexes. The first in vitro active complexes were designed to emulate the cis-platin frame work, with the composition SnR2X2 and SnR2X2L2 (X = halide or pseudohalide, R = organic group, and L = a nitrogen ligand such as Py, or L2 = a bidentate nitrogen ligand such as en, bipy, phen, etc.), but they exhibited low solubility, low activity, and high toxicity in vivo. During recent decades, several organotins with different structures and anti-neoplastic activity toward the mammarian cancer cell lines have been developed. The mode of action of most organotin compounds is displayed via different mechanism at molecular level. Many of them seem to bind DNA. Moreover, the R2Sn2+ and R3Sn+ moieties (R = alkyl or aryl group) are the active species, and they may bind to thiol groups of proteins. However, it has been reported recently that low doses of organotins can exhibit anti-cancer activity via a gene-mediated pathway in the cancer cells. A number of di- and tri-n-butyltin chloride compounds induce apoptosis in vitro in rat thymocytes through inhibition of DNA synthesis while increasing RNA synthesis. Owing to such a structural specificity, we have directed our systematic efforts to words the chemotherapeutic importance of organotin(IV) derivatives of biomolecules and development of new organotin(IV) derivatives of amino acids, fatty acids, Schiff bases derived from amino acids, peptides, nucleobases and nucleotides, 7-hydroxycoumarin and ascorbic acid. Some of these have been found to be very active in vitro against cancer cell lines of human origin, viz. MEL A498 renal cancer, EVSA-T mammary cancer, H-226 lung cancer, IGRV ovarian cancer, MCF-7 mammary cancer, and WiDr colon cancer in comparison to 5-fluorouracil, cis-platin, carboplatin and etoposide, but less active as compared to doxorubicin, methotrexate and taxol. Recent findings and results indicate that they induce apoptosis through the inhibition of DNA synthesis. Furthermore, every health problem or disease is associated with pain; therefore, any anticancer drug with good anti-inflammatory activity will be more beneficial. Some of the studied compounds exhibit potent anti-inflammatory activity in vivo with very mild or no side effects on cardiovascular system, and have toxicity LD50 ~ 500–1000 mg kg-1 with wider safety margin. More recent results suggest that in designing new anticancer organotin compounds it is important to individuate a balance between solubility and lipophilicity in order to achieve efficacy of the drug. Also, the reduction of side effects, such as neurotoxicity and immune suppression, should be considered, so the search for species which are more selective, and efficient at low dosage, represents a challenge.
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