Genetic variability & chemotoxicity of 5-fluorouracil & cisplatin in head & neck cancer patients: a preliminary study.

Background & objectives: The efficacy and toxicity of a given chemotherapy regimen varies widely among patients due to the inherited variability of genes that are involved in drug metabolism. There are several crucial enzymes identified involving metabolism of 5-fluorouracil (5-FU) and cisplatin, which are polymorphic. We studied head and neck cancer patients (n=23) on 5-FU and cisplatin combination therapy attending a tertiary care cancer research institute in Gujarat, India, to understand the effect of a particular genotype on toxicity. Methods: The patients were genotyped for dihydropyrimidine (DPYD) (85T>C, IVS14+1G>A, 2846A>T, 2194G>A), thymidylate synthase (TYMS) [28bp tandem repeat in the promoter enhancer region (TSER)], methylenetetrahydrofolate reductase (MTHFR) (677C>T, 1298A>C), glutathione S-transferase P1(GSTP1) (Ile105Val), glutathione S-transferase T1 (GSTT1) (null allele) and glutathione S-transferase M1 (GSTM1) (null allele) by multiplex allele-specific PCR and long range PCR. Results: Of the 23 (19 males 4 females, age range 18-16 yr) patients, two had grade 3 and 4 toxicity while the remaining 21 had 0 to 2 grade toxicity after treatment with 5-FU and cisplatin combination therapy. An association between the genotype of GSTM1 (+/- and -/-) and the toxicity of cisplatin (P=0.043) was observed. Interpretation & conclusions: The findings of this preliminary study suggested an association between the variants of GSTM1 and toxicity observed due to cisplatin. Well planned studies on a large sample of head and neck cancer patients need to be conducted to understand the effects of these genetic variants on toxicity and efficacy of anticancer drugs.

Identification and characterization of lipids from endosomes purified by electromagnetic chromatography.

Traditional separation techniques do not yield endolysosomes of sufficient purity to permit detailed biochemical characterization of this important class of intracellular vesicles. Here, we have used a magnetic chromatography technique to isolate the endosomes from rat peritoneal macrophages and studied their lipid composition. Electromagnetic isolation works by retention of colloidal iron containing vesicles on magnetic column. The data suggested that both early and late endosomes were rich in cholesterol, whereas sphingomyelin (SM) and specific phospholipids like phosphatidylcholine. phosphatidylethanolamine, phosphatidylglycerol and phosphatidylserine are enriched in the late compartments. Our results also indicated that the purified fractions are enriched in raft lipids like SM, but not in cholesterol. The endosomal purification method described here yields pure endosomes with little or no contamination from mitochondria and hence could be used for further biochemical and marker analysis, giving insight into mechanisms of endocytic traffic.

Programmed cell death and its clinical implications.

Cell death is a highly regulated process that is ubiquitous in all eukaryotes. Programmed cell death (PCD) is an integral part of both animal and plant development. Studies on apoptosis, the well characterized form of programmed cell death led to the identification of a central tripartite death switch i.e. apoptosome consisting of Apaf-1, Apaf-2 and Apaf-3. The caspases, a family of cysteine-dependent aspartate directed-proteases, constitute the central executioners of apoptosis. Much of the attention on programmed cell death is focused on caspases, however, cell death can still occur even when the caspase cascade is blocked, revealing the existence of nonapoptotic alternative pathway(s) of cell death. The mitochondrial release of cytochrome C following a PCD inducing stimulus in both plants and animals suggests the evolutionary conservation of death pathways. Dysregulation of apoptosis may be related to the development of several disease states as well as ageing. Excessive apoptosis is associated with neurodegenerative disorders, AIDS etc., whereas deficient apoptosis is associated with cancer, auto-immunity, viral infections etc. Understanding the regulation of programmed cell death would throw light in designing drugs and gene therapies that can target specific molecules in the apoptotic pathway opening the vistas for new therapeutic endeavors in many areas of medicine.