A genome-wide association scan on estrogen receptor-negative breast cancer

Introduction

Breast cancer is a heterogeneous disease and may be characterized on the basis of whether estrogen receptors (ER) are expressed in the tumour cells. ER status of breast cancer is important clinically, and is used both as a prognostic indicator and treatment predictor. In this study, we focused on identifying genetic markers associated with ER-negative breast cancer risk.

Methods

We conducted a genome-wide association analysis of 285,984 single nucleotide polymorphisms (SNPs) genotyped in 617 ER-negative breast cancer cases and 4,583 controls. We also conducted a genome-wide pathway analysis on the discovery dataset using permutation-based tests on pre-defined pathways. The extent of shared polygenic variation between ER-negative and ER-positive breast cancers was assessed by relating risk scores, derived using ER-positive breast cancer samples, to disease state in independent, ER-negative breast cancer cases.

Results

Association with ER-negative breast cancer was not validated for any of the five most strongly associated SNPs followed up in independent studies (1,011 ER-negative breast cancer cases, 7,604 controls). However, an excess of small P-values for SNPs with known regulatory functions in cancer-related pathways was found (global P = 0.052). We found no evidence to suggest that ER-negative breast cancer shares a polygenic basis to disease with ER-positive breast cancer.

Conclusions

ER-negative breast cancer is a distinct breast cancer subtype that merits independent analyses. Given the clinical importance of this phenotype and the likelihood that genetic effect sizes are small, greater sample sizes and further studies are required to understand the etiology of ER-negative breast cancers.

C-peptide response in patients on insulin therapy

This study was undertaken to document clinical features and presentation of Type I diabetes and to study beta cell response in these patients. It provides data on 30 insulin treated patients. Type I diabetes presents most commonly in the 20-40 year age group. A positive family history in first degree relatives was noted in 40%. The commonest complications were retinopathy (63%) and peripheral neuropathy (53%). Proteinuria (10%), ischaemic heart disease (13%) and peripheral vascular disease (13%) were less common. Three kinds of response to C-peptide were noted: 1) no response 2) blunted response (below the normal range) and 3) peak response to glucose within the low normal range. Group 3 probably represents Type II insulin treated diabetes. There was poor correlation between fasting blood glucose and basal or peak C-peptide response, or with duration or complications of diabetes. C-peptide response may be used to differentiate Type I from Type II diabetes.