Genetic polymorphisms potentially associated with response to metformin in postmenopausal diabetics suffering and not suffering with cancer

Metformin is a well-known antidiabetic medication, which, besides diabetes, may be involved into modulation of other age-related pathologies, including cancer. The study concerns 12 gene polymorphisms divided into 2 groups consisting of 6 genes each. The first group was composed from so-called "standard" (S) polymorphisms, for which the connection with metabolic response to metformin is already established. The second group included polymorphisms of genes encoding proteins possibly connected with diabetes mellitus type 2 (DM2), impaired glucose tolerance or cancer and entitled here as "associated" (A). A total of 156 postmenopausal women (average age 60.7 ± 0.7) were included, 37 of them healthy, 64 with type DM2 and concurrent treatment-naïve cancer (mostly breast, endometrial or colorectal cancer), 32 with DM2 without cancer, and 23 with treatment-naïve cancer and normal glucose tolerance. The leading metformin response S-marker in combined group of DM2 patients was the CC variant of OCT1-R61C polymorphism of organic cation transporter protein 1 gene. In cancer patients without DM2, this position belonged to AC and AA genotypes of OCT1_rs622342 polymorphism. Among the A-polymorphisms, GA variant of sex hormone-binding globulin gene SHBG_D356N was less frequently observed in DM2 patients with or without cancer. Besides, in diabetics, the same polymorphic variant of SHBG as well as GC genotype of oxidized lipoprotein receptor OLR1_G501C and GG genotype of locus rs11065987 near BRAP gene were carried rather often in combination with "metformin-positive" variant of OCT1_R61C. In addition, carriers of OCT1_R61C and OCT1_rs622342 polymorphisms with potentially positive reaction to metformin had higher insulin resistance score (HOMA-IR) values. Received data lead to the conclusion that postmenopausal diabetics, both with and without cancer, differ in genetic stigmata of potential response to metformin less than they differ from cancer patients without DM2. As genetic polymorphisms associated with metabolic and anticancer metformin (and, possibly, phenformin) effects may be different, this subject requires further investigation.

Association between insulin receptor substrate 1 Gly972Arg polymorphism and cancer risk

Epidemiological studies investigating the association between the insulin receptor substrate 1 (IRS1) gene Gly972Arg (rs1801278) polymorphism and various carcinomas risk reported conflicting results. Thus, a systemic review and meta-analysis of published studies were performed to assess the possible association. A comprehensive search was conducted to identify all eligible studies of IRS1 Gly972Arg polymorphism and cancer risk. Odds ratios (ORs) and 95 % confidence intervals (CIs) were used to assess the strength of the associations. A total of 16 independent studies, including 11,776 cases and 11,654 controls, were identified. When all studies were pooled, we found a significant association between IRS1 Gly972Arg polymorphism and increased cancer risk under dominant model (OR = 1.16, 95 %CI = 1.04-1.30, P = 0.007) and allelic model (OR = 1.16, 95 %CI = 1.02-1.30, P = 0.02). In subgroup analysis based on cancer type, increased cancer risk was found in ovarian cancer (dominant: OR = 1.55, 95 %CI = 1.17-2.05, P = 0.002; allelic: OR = 1.55, 95 %CI = 1.19-2.01, P = 0.001), breast cancer (allelic: OR = 1.12, 95 %CI = 1.00-1.26, P = 0.05), and other cancers (allelic: OR = 1.31, 95 %CI = 1.00-1.71, P = 0.05). When stratified by study types, significant associations were observed in both cohort studies (dominant: OR = 1.25, 95 %CI = 1.06-1.47, P = 0.007; allelic: OR = 1.25, 95 %CI = 1.07-1.46, P = 0.005) and case-control studies (dominant: OR = 1.15, 95 %CI = 1.01-1.31, P = 0.04). In the subgroup analyses by ethnicity, significantly increased cancer risk was suggested among both Caucasians (dominant: OR = 1.13, 95 %CI = 1.02-1.26, P = 0.02; allelic: OR = 1.13, 95 %CI = 1.03-1.25, P = 0.01) and mixed population (dominant: OR = 1.22, 95 %CI = 1.01-1.46, P = 0.04). Our investigations demonstrate that IRS1 Gly972Arg polymorphism was associated with an increased risk of cancer, and additional well-designed studies are warranted to validate these findings.

Polymorphisms in three obesity-related genes (LEP, LEPR, and PON1) and breast cancer risk: a meta-analysis

Common genetic variations in the leptin (LEP), leptin receptor (LEPR), and paraoxonase 1 (PON1) genes have been considered to be implicated in the development of breast cancer. However, the results were inconsistent. In this study, a meta-analysis was performed to assess the associations of five polymorphisms, including LEP G2548A, LEPR Q223R, LEPR Lys109Arg, PON1 L55M, and PON1 Q192R polymorphisms, with breast cancer risk. Published literature from PubMed, ISI Web of Science, Embase databases, CNKI, and Wanfang Data were retrieved. All studies evaluating the association between LEP G2548A, LEPR Q223R, LEPR Lys109Arg, PON1 L55M, or PON1 Q192R polymorphism and breast cancer risk were included. Pooled odds ratio (OR) with 95% confidence interval (CI) was calculated using fixed- or random-effects model. Three studies (2,003 cases and 1,967 controls) for LEP G2548A polymorphism, nine studies (4,627 cases and 5,476 controls) for LEPR Q223R polymorphism, five studies (2,759 cases and 2,573 controls) for LEPR Lys109Arg polymorphism, four studies (1,517 cases and 1,379 controls) for PON1 L55M polymorphism, and five studies (1,575 cases and 2,283 controls) for PON1 Q192R polymorphism were included in the meta-analysis. Overall, the results showed null significant association between LEP G2548A, LEPR Q223R, LEPR Lys109Arg, or PON1 Q192R polymorphism and breast cancer risk; however, PON1 L55M was significantly associated with breast cancer risk overall (MM vs. LL: OR = 2.16; 95% CI, 1.76-2.66). For LEPR Q223R polymorphism, further subgroup analysis suggested that the association was only statistically significant in East Asians (OR = 0.50; 95% CI, 0.36-0.70) but not in Caucasians (OR = 1.06; 95% CI, 0.77-1.45) or Africans (OR = 1.30; 95% CI, 0.83-2.03). The present meta-analysis suggested that LEPR Q223R polymorphism might be implicated in the development of breast cancer in East Asians; PON1 L55M might increase breast cancer risk. However, given the limited sample size, the findings warrant further investigation.