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LIFE09200604007 Tabish - Homi Bhabha National Institute

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Review of Literature<br />

of 31 published case-control associations of GSTT1 null genotype along with GSTM1<br />

null genotype with head and neck cancer risk was observed 149 . Apart from this, in<br />

Indian population as well GSTT1 null genotype has emerged as associated with risk of<br />

upper aero digestive tract cancers 143, 150 . On the contrary a large Indian study has<br />

shown GSTT1 to be significantly protective in oral cancer patients with tobacco habit<br />

151 .<br />

GSTP1 (Glutathione-S-Transferase-Pi 1)<br />

The gene encodes an enzyme belonging to GST pi class. GSTP1-exon5<br />

Ile 105 Val polymorphism is extensively studied in terms of association with cancer 152 .<br />

This polymorphism is reported to confer risk of upper aero digestive tract cancers<br />

among Indians along with other GSTT1 and GSTM1 polymorphism 153 . In addition<br />

GST profile may have a prognostic value since it is associated with the response to<br />

therapy in human malignancies 148, 154, 155 . GSTP1 Ile 105 Val polymorphism is found to<br />

be associated with modestly increased risk of second primary malignancy after index<br />

head and neck squamous cell carcinomas 44 .<br />

SULT1A1 (Sulfotransferase 1A1)<br />

The gene encodes sulfotransferase enzyme that belongs to phase II carcinogen<br />

detoxifying enzyme category. It catalyzes the sulfate conjugation of many hormones,<br />

neurotransmitters, drugs, and carcinogenic compounds resulting in increased polarity<br />

and solubility of the compound that facilitates excretion of carcinogens through bile or<br />

urine. SULT1A1-exon7 Arg 213 His polymorphism is very extensively studied and is<br />

found to be associated with head and neck cancer and lung cancer risk 156, 157 . Our study<br />

of meta-analysis of 33 case control studies showed His/His 213 genotype to confer<br />

significant risk UADT cancers 12 .<br />

MPO (Myeloperoxidase)<br />

It activates wide range of tobacco smoke procarcinogens such as<br />

benzo[a]pyrene and aromatic amines into activated carcinogens. The -463G>A SNP<br />

occurs in the MPO promoter region leading to decreased expression and activity 158 .<br />

The variant allele of MPO is shown to have mixed effect on cancer risk. It is reported<br />

that subjects bearing the A/G or A/A allele have a reduced risk to suffer from advanced<br />

lung cancer and esophageal cancer 159, 160 . Where as in other reports genetic effect of<br />

48

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