DNA polymerase β deficiency is linked to aggressive breast cancer: a comprehensive analysis of gene copy number, mRNA and protein expression in multiple cohorts

Short arm of chromosome 8 is a hot spot for chromosomal breaks, losses and amplifications in breast cancer. Although such genetic changes may have phenotypic consequences, the identity of candidate gene(s) remains to be clearly defined. Pol β gene is localized to chromosome 8p12-p11 and encodes a key DNA base excision repair protein. Pol β may be a tumour suppressor and involved in breast cancer pathogenesis. We conducted the first and the largest study to comprehensively evaluate pol β in breast cancer. We investigated pol β gene copy number changes in two cohorts (n = 128 &n = 1952), pol β mRNA expression in two cohorts (n = 249 &n = 1952) and pol β protein expression in two cohorts (n = 1406 &n = 252). Artificial neural network analysis for pol β interacting genes was performed in 249 tumours. For mechanistic insights, pol β gene copy number changes, mRNA and protein levels were investigated together in 128 tumours and validated in 1952 tumours. Low pol β mRNA expression as well as low pol β protein expression was associated high grade, lymph node positivity, pleomorphism, triple negative, basal-like phenotypes and poor survival (ps < 0.001). In oestrogen receptor (ER) positive sub-group that received tamoxifen, low pol β protein remains associated with aggressive phenotype and poor survival (ps < 0.001). Artificial neural network analysis revealed ER as a top pol β interacting gene. Mechanistically, there was strong positive correlation between pol β gene copy number changes and pol β mRNA expression (p < 0.0000001) and between pol β mRNA and pol β protein expression (p < 0.0000001). This is the first study to provide evidence that pol β deficiency is linked to aggressive breast cancer and may have prognostic and predictive significance in patients.

Superficial fungal infections seen at a tertiary health centre: clinical and mycological studies

BACKGROUND

Superficial fungal infections are common in the tropics, partly due to the climate, relatively poor hygiene, and lifestyle of the people.

OBJECTIVE

To determine the clinical forms and aetiological agents of superficial fungal infections as seen among skin cases in the north- central part of Nigeria.

METHODS

All consecutive new patients seen at the skin clinic of the General Out-patient Department of the Federal Medical Centre, Bida from July 2006 to December 2007 were included in this prospective study. Participants were examined for superficial fungal lesions. Samples of skin scrapings for microbiological investigations were obtained from suspicious lesions.

RESULTS

A total of 381 patients attended the Skin Clinic during the period of study. Superficial fungal infections constituted 89(23.4%) of all skin cases seen. The commonest clinical type of fungal infection was Tinea corporis, followed by Tinea unguium. Male to female ratio of clinical lesions was 1: 1.5. A total of 41 samples grew fungal organisms on Sabouraud Dextrose Agar culture, of which dermatophytes were the isolates in 22(53.7%), while non-dermatophytes accounted for the rest. Seven species of dermatophytes, dominated by Trichophyton spp. 15 (68.2%), followed by Microsporum gypseum 4(18.2%), and Epidermophyton floccosum 3(13.6%) were the main isolates. The most commonly recovered species were T. mentagrophytes (36.4%).

CONCLUSION

These data show the continued predominance of dermatophytes as the principal pathogen in superficial fungal infection. Trichophyton spp. is the predominant class of which T. mentagrophyte is the most prevalent.