The CAG repeat polymorphism in the androgen receptor gene (AR) and its relationship to head and neck cancer

Digital biomarker 2D:4D as a predictor of cancer: A systematic review

BACKGROUND

The digital ratio between the second and fourth digits of the hands, known as 2D:4D, is sexually dimorphic. It has been suggested that a low 2D:4D indicates high exposure to prenatal testosterone and low estrogen exposure while a high 2D:4D indicates the inverse. The 2D:4D may be predictive of cancer susceptibility, and this may be particularly true in cancers that show differences between sexes in their occurrence.

AIM

To conduct a systematic review of published epidemiological literature examining the association between 2D:4D and cancer.

METHOD

This review was carried out according to criteria recommended for the systematic review of Statement PRISMA. We enrolled 25 papers involving eleven cancer topographies with 4,569 cases and 19,416 controls from Europe, America, Asia and Australia.

RESULTS

We noticed variations and discrepancies in the results of the association between 2D:4D and cancer among the studies, either in those that had evaluated the same or different types of cancer, or in the same or distinct lateralities. However, a high 2D:4D was considered a likely predictor of cancer risk in 11 of 25 studies, a low 2D:4D was suggested as a predictor of risk in eight papers, and five of the twenty-five studies did not demonstrate any association.

CONCLUSIONS

Although this biomarker has the advantage of being easy to measure, it is noted that its relationship with sex hormone levels at specific stages of life has not yet been well quantified, and it has still been questioned. Hence, it is suggested that those findings from studies involving 2D:4D as a proxy for foetal hormone exposure should be interpreted with caution, as well as those studies which claim its association with cancer. Thus, this review shows the need for a greater number of epidemiological studies using more homogeneous methodology and techniques to better investigate the strength of the findings.

Oestrogens and androgen receptors in oral squamous cell carcinoma

OBJECTIVE

To investigate the gender-related expressions of androgen (AR), estrogen alpha (ERα) and beta (ERβ) receptors and aromatase enzyme in oral squamous cell carcinomas (OSCC).

MATERIALS AND METHODS

A total of 60 cases of OSCC (30 from males and 30 from females) were retrieved and submitted to immunohistochemistry. Also, steroid expression was studied in two OSCC cell lines using Western blotting and immunofluorescence.

RESULTS

Immunohistochemistry demonstrated that ERβ was expressed in almost 40% of the cases and AR in 26%. Aromatase enzyme and ERα were less commonly expressed. Only AR presented statistically significant differences between genders. Western blotting and immunofluorescence analysis demonstrated that ERβ was abundantly expressed in the nuclei of both cell lines and aromatase enzyme presented a cytoplasmic expression.

CONCLUSION

The detection of steroid hormones, especially ERβ, can indicate a role of these proteins in the process of carcinogenesis of some OSCC. Further studies of the mechanisms involved may provide important biological information regarding therapeutic approaches.

Expression of sexual hormones receptors in oral squamous cell carcinoma

Sexual hormones play an important role in expression of genes involved in a wide variety of biological and neoplastic processes. The information on Estrogen Receptors (ER) expression in non-target tissues is very few and, in particular, the studies in head and neck tumors are still controversial. Recent studies analyzed the role of Tamoxifen (TAM) on Oral Squamous Cell Carcinoma (OSCC) lines in relation to the presence/absence of ER. The purpose of the present study was to evaluate the expression of sexual hormones receptors mRNAs, in particular Estrogen Receptor alpha (ERα) and Androgen Receptor (AR) mRNA in OSCC tissues. The study group comprised 20 samples of OSCC, harvested from 20 otherwise healthy subjects (14 males and 6 females, mean age 58.2y, range 38-74). The control group was formed by 20 samples of normal mucosa harvested around the margins of the specimens (at least 1 cm from the lesion margins). Estrogens Receptor alpha (Era) and Androgen Receptor (AR) mRNA expressions were analyzed by RT-PCR carried out on total RNAs extracted from both cancerous and healthy tissues. Obtained data were evaluated by Shapiro-Walk normality test and compared by Student's t test. Results with p<0.05 were considered statistically significant. AR transcripts were less expressed in OSCC specimens than in healthy tissues, while levels of ERα transcripts significantly increased in tumor samples. These preliminary data show different expression patterns of AR and ERα mRNAs in malignant tissues of oral mucosa and could suggest an involvement of these sexual hormones in oral cancer.

Right hand digit ratio (2D:4D) is associated with oral cancer

Finger length ratio has been proposed as a putative marker for prenatal hormone exposure, as well as the action of HOX, AR, and a variant of the LIN28b genes. These genes have been recently connected to carcinogenesis and digit ratio could help to identify patients with this predisposition.

OBJECTIVES

The purpose of this study was to investigate the possible correlations between digit ratio, oral squamous cell carcinoma (OSCC)-the most common oral cancer-and oral premalignant lesions (OPLs) in tobacco-consuming males, the main risk group for this disease.

METHODS

Digital images of the right hands of patients diagnosed with OSCC (n = 25), OPLs (n = 25), and age-matched controls (n = 25) were obtained. Fingers were measured using Adobe Photoshop and the mean ratios between the 2nd and 4th digits were compared. Data were analyzed by ANOVA (α = 0.05).

RESULTS

Risk factors (alcohol and tobacco consumption, familial history) were similar between the three study groups. Males in the OSCC group presented significantly higher digit ratio (P = 0.03) in comparison with males with OPLs and individuals without oral lesions.

CONCLUSIONS

According to the results, males with the higher digit ratio seem to be more prone to undergo malignization of lesions in the oral cavity. Similar deleterious habits for the three groups allows us to infer that digit ratio could add to the research of etiological factors and be a putative marker for the screening of patients' susceptibility to develop oral squamous cell carcinoma.

Shorter CAG repeat length in the AR gene is associated with poor outcome in head and neck cancer

OBJECTIVE

Alterations in the size of the [CAG](n) repeats of the AR gene have been described in several types tumors. The purpose of this study was to evaluate if there is an association between the AR [CAG](n) repeat alleles and the relative risk for head and neck cancer and to analyse microsatellite instability (MSI) and loss of heterozygosity (LOH) in these tumors.

DESIGN

Matched samples of blood and head and neck tumors were evaluated using two methodologies, silver-stained gels to perform the analyses of MSI and LOH, and automated analysis to confirm these results and for genotyping of the AR [CAG](n) repeat length. Sixty-nine individuals without cancer were used as a control group for both procedures. The Log-rank test was used to compare overall survival and disease-free survival curves. The Cox proportional hazards regression models were performed to determine the [CAG](n) repeats as an independent prognostic factor.

RESULTS

Patients with alleles <or=20 in the male group showed a correlation with lower disease-free survival (P=0.0325) and with recurrence or metastasis (RR 2.52, CI 95%). In the female group, the allele 2 (longer allele) showed a significant lower mean of [CAG](n) repeat when compared to the control group. Microsatellite instability was detected in nine cases in both procedures. In six out of these nine cases, we observed a reduction of the AR [CAG](n) repeat length. LOH was detected in one out of 17 women informative for oral cancer in both procedures.

CONCLUSION

These results suggest that short [CAG](n) repeat length (<or=20) polymorphism is associated with poor prognosis in a subset of male patients with head and neck cancer and that AR gene microsatellite instability is uncommon in these tumors.

Phenotypic heterogeneity of mutations in androgen receptor gene

Androgen receptor (AR) gene has been extensively studied in diverse clinical conditions. In addition to the point mutations, trinucleotide repeat (CAG and GGN) length polymorphisms have been an additional subject of interest and controversy among geneticists. The polymorphic variations in triplet repeats have been associated with a number of disorders, but at the same time contradictory findings have also been reported. Further, studies on the same disorder in different populations have generated different results. Therefore, combined analysis or review of the published studies has been of much value to extract information on the significance of variations in the gene in various clinical conditions. AR genetics has been reviewed extensively but until now review articles have focused on individual clinical categories such as androgen insensitivity, male infertility, prostate cancer, and so on. We have made the first effort to review most the aspects of AR genetics. The impact of androgens in various disorders and polymorphic variations in the AR gene is the main focus of this review. Additionally, the correlations observed in various studies have been discussed in the light of in vitro evidences available for the effect of AR gene variations on the action of androgens.