Impact of GSTM1, GSTT1 and GSTP1 genes polymorphisms on clinical toxicities and response to concomitant chemoradiotherapy in cervical cancer

Predictive Factors for Toxicity After Primary Chemoradiation for Locally Advanced Cervical Cancer: A Systematic Review

PURPOSE

Women with locally advanced cervical cancer (LACC) undergoing primary platinum-based chemoradiotherapy and brachytherapy often experience toxicities. Normal-tissue complication probability (NTCP) models quantify toxicity risk and aid in optimizing radiation therapy to minimize side effects. However, it is unclear which predictors to include in an NTCP model. The aim of this systematic review was to provide an overview of the identified predictors contributing to gastrointestinal (GI), genitourinary (GU), and vaginal toxicities and insufficiency fractures for LACC.

METHODS AND MATERIALS

A systematic search was performed and articles evaluating the relationship between predictors and toxicities in women with LACC treated with primary chemoradiation were included. The Quality In Prognosis Studies tool was used to assess risk of bias, with high-risk studies being excluded from further analysis. Relationships between dose-volume parameters, patient and treatment characteristics, and toxicity endpoints were analyzed.

RESULTS

Seventy-three studies were identified. Twenty-six had a low or moderate risk of bias and were therefore included. Brachytherapy-related dose-volume parameters of the GI tract, including rectum and bowel equivalent dose in 2 Gy fractions (EQD2) D2 cm3, were frequently related to toxicities, unlike GU dose-volume parameters. Furthermore, (recto)vaginal point doses predicted toxicities. Few studies evaluated external beam radiation therapy dose-volume parameters and identified rectum EQD2 V30 Gy, V40 Gy, and V55 Gy, bowel and bladder EQD2 V40 Gy as toxicity predictors. Also, total reference air kerma and vaginal reference length were associated with toxicities. Relationships between patient characteristics and GI toxicity were inconsistent. The extent of vaginal involvement at diagnosis, baseline symptoms, and obesity predicted GU or vaginal toxicities. Only 1 study evaluated insufficiency fractures and demonstrated lower pretreatment bone densities to be associated.

CONCLUSIONS

This review detected multiple candidate predictors of toxicity. Larger studies should consider insufficiency fractures, assess dose levels from external beam radiation therapy, and quantify the relationship between the predictors and treatment-related toxicities in women with LACC to further facilitate NTCP model development for clinical use.

Genetic and epigenetic alterations in DNA repair genes and treatment outcome of chemoradiotherapy in cervical cancer

Cervical cancer (CaCx) is the deadliest malignancy among women which is caused by human papillomavirus (HPV) and anthro-demographical/clinicopathological factors. HPV oncoproteins E6 and E7 target p53 and RB (retinoblastoma) protein degradation, Ataxia telangiectasia mutated (ATM), ATM-RAD3-related (ATR) inactivation and subsequent impairment of non-homologous end joining (NHEJ), homologous recombination, and base excision repair pathways. There is also an accumulation of genetic and epigenetic alterations in Tumor Growth Suppressors (TGS), oncogenes, and DNA repair genes leading to increased genome instability and CaCx development. These alterations might be responsible for differential clinical response to Cisplatin-based chemoradiotherapy (CRT) in patients. This review explores HPV-mediated DNA damage as a risk factor in CaCx development, the mechanistic role of genetic and epigenetic alterations in DNA repair genes and their association with CRT and outcome, It also explores new possibilities for the development of genetic and epigenetic-based biomarkers for diagnostic, prognostic, and molecular therapeutic interventions.

Individual effects of GSTM1 and GSTT1 polymorphisms on cervical or ovarian cancer risk: An updated meta-analysis

Background: Studies have shown that glutathione S-transferase M1 (GSTM1) and. glutathione S-transferase T1 (GSTT1) null genotype may increase the risk of cervical cancer (CC) or ovarian cancer (OC), however, the results of published original studies and meta-analyses are inconsistent. Objectives: To investigate the association between GSTM1 present/null and GSTT1 present/null polymorphisms, with the risk of cervical cancer or ovarian cancer. Methods: The odds ratios (ORs) and 95% confidence intervals (CIs) were used to assess the association between GSTM1 present/null and GSTT1 present/null polymorphisms and the risk of cervical cancer or ovarian cancer. To assess the confidence of statistically significant associations, we applied false positive reporting probability (FPRP) and bayesian false discovery probability (BFDP) tests. Results: Overall analysis showed that GSTM1 null was associated with an increased risk of cervical cancer, and subgroup analysis showed a significant increase in cervical cancer risk in Indian and Chinese populations; GSTT1 was not found null genotype are significantly associated with cervical cancer. Overall analysis showed that GSTM1 and GSTT1 null were not associated with the risk of ovarian cancer, subgroup analysis showed that GSTM1 null was associated with an increased risk of OC in East Asia, and GSTT1 null was associated with an increased risk of OC in South America. However, when we used false positive reporting probability and bayesian false discovery probability to verify the confidence of a significant association, all positive results showed "low confidence" (FPRP > .2, BFDP > .8). Conclusion: Overall, this study strongly suggests that all positive results should be interpreted with caution and are likely a result of missing plausibility rather than a true association.

Impact of genetic factors on platinum-induced gastrointestinal toxicity

Severe gastrointestinal (GI) toxicity is a common side effect after platinum-based chemotherapy. The incidence and severity of GI toxicity vary among patients with the same chemotherapy. Genetic factors involved in platinum transport, metabolism, detoxification, DNA repair, cell cycle control, and apoptosis pathways may account for the interindividual difference in GI toxicity. The influence of gene polymorphisms in the platinum pathway on GI toxicity has been extensively analyzed. Variations in study sample size, ethnicity, design, treatment schedule, dosing, endpoint definition, and assessment of toxicity make it difficult to precisely interpret the results. Hence, we conducted a review to summarize the most recent pharmacogenomics studies of GI toxicity in platinum-based chemotherapy and identify the most promising avenues for further research.

Drug-target-ADR Network and Possible Implications of Structural Variants in Adverse Events

Adverse drug reactions (ADRs) are of major concern in drug safety. However, due to the biological complexity of human systems, understanding the underlying mechanisms involved in development of ADRs remains a challenging task. Here, we applied network sciences to analyze a tripartite network between 1000 drugs, 1407 targets, and 6164 ADRs. It allowed us to suggest drug targets susceptible to be associated to ADRs and organs, based on the system organ class (SOC). Furthermore, a score was developed to determine the contribution of a set of proteins to ADRs. Finally, we identified proteins that might increase the susceptibility of genes to ADRs, on the basis of knowledge about genomic structural variation in genes encoding proteins targeted by drugs. Such analysis should pave the way to individualize drug therapy and precision medicine.

British Journal of Biomedical Science in 2019. What have we learned?

In 2019 the British Journal of Biomedical Science published 40 articles in the various disciplines that comprise biomedical science. These were one review, 22 original articles and 17 'In Brief' short reports. Of those citing original data, the majority were in cellular pathology (14 papers), clinical chemistry (9 papers), and microbiology (6 papers: 4 in bacteriology and 2 in virology). There were 3 papers in haematology and 2 in andrology, whilst 5 papers crossed traditional discipline boundaries (such as the molecular genetics of IL6, liver function tests, and hepatocellular carcinoma). Over two-thirds of papers used techniques in molecular genetics. The present report will summarise key aspects of these publications that are of greatest relevance to laboratory scientists.

Interaction of antioxidant gene variants and susceptibility to type 2 diabetes mellitus

Background: Diabetes is the seventh most common disease leading to death with a global estimate of 425 million diabetics, expected to be 629 million in 2045. The role of reactive metabolites and antioxidants, such as glutathione, glutathione peroxidase, superoxide dismutase and catalase in type 2 diabetes mellitus (T2DM) provides an opportunity for identifying gene variants and risk genotypes. We hypothesised that certain antioxidant gene-gene interactions are linked with T2DM and can model disease risk prediction.Materials and methods: Genotyping of single nucleotide polymorphisms (SNPs) in antioxidant genes for glutathione (GST), glutathione peroxidase (GPx), superoxide dismutase (SOD) and catalase (CAT) was performed in 558 T2DMs and 410 age and sex matched healthy controls by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), routine lab indices by standard techniques.Results: The null/null allele combination of GSTM1del and GSTT1del increased disease risk up to 1.7-fold. The combination of SNPs in GSTM1del, GSTT1del, GSTP1 + 313A/G and in CAT-21A/T, SOD2 + 47C/T, GPx1 + 599C/T increased the risk of diabetes 13.5 and 2.1-fold, respectively. Interaction of SNPs GSTM1del, GSTT1del, GSTP1 + 313A/G (105Ile/Val), CAT-21A/T, SOD2 + 47C/T, GPx1 + 599C/T were significantly linked with disease risk >5 × 10³ fold.Conclusion: As the number of gene combinations increase, there is a rise in the odds ratio of disease risk, suggesting that gene-gene interaction plays an important role in T2DM susceptibility. Individuals who possess the GSTM1del, GSTT1del, GSTP1 105I/V(+313A/G), CAT-21A/T, SOD2 + 47C/T and GPx1 + 599C/T are at very high risk of developing T2DM.

Genetic polymorphisms in DNA repair genes and their association with cervical cancer

Background and objective: Carcinoma of cervix is the second most common cancer among women worldwide. The DNA repair network plays an important role in the maintenance of genetic stability, protection against DNA damage and carcinogenesis. Alterations in repair genes XRCC1, XRCC2 and XRCC3 and been reported in certain cancers. We hypothesised an association between XRCC1+399A/G, XRCC2+31467G/A and XRCC3+18067C/T polymorphisms and the risk of cervical cancer. Subjects and methods: This study included 525 subjects (265 controls and 260 cervical cancer cases). Genotypes were determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Results: Women with GA and AA genotypes of XRCC1+399A/G showed 2.4-3.8 fold higher risk of cervical cancer (P = 0.001). The +399A* allele was significantly linked with cervical cancer (P = 0.002). However, XRCC2+31479G/A and XRCC3+18067C/T polymorphisms did not show any statistically significant associations. Conclusion: The XRCC1+399A/G SNP is linked with cervical cancer. We suggest that this variant can be utilized as a prognostic marker for determination of cervical cancer susceptibility.

British Journal of Biomedical Science in 2018: what have we learned?

In 2018 the British Journal of Biomedical Science published one guideline (in reproductive science) and 40 research articles in the various disciplines the comprise biomedical science. The latter were 24 original articles and 16 'In Brief' short reports. Of these, 23 are of note to only one of the sub-disciplines (seven each to biochemists and microbiologists, six to cell pathologists, and one each to cytologists, immunologists and reproductive scientists). Reflecting the increasing complexity of laboratory science, thirteen papers crossed one boundary (three papers each relevant to biochemists and immunologists, and to haematologists and biochemists), whilst four papers were relevant to three or more disciplines. Indeed, biochemical techniques were used in 18 papers, microbiological techniques in 9, whilst histopathology was relevant to 11 papers. Notably, 20 papers used techniques in chromosome analysis and molecular genetics. The present report will summarise key aspects of these publications that are of greatest relevance to laboratory scientists.