Review of Polymorphism of the Calcium-Sensing Receptor Gene and Breast Cancer Risk.

Polymorphism of the calcium-sensing receptor gene (CaSR or CaR) has been associated with an increased risk for breast cancer. This receptor plays an important role in calcium homeostasis, and has also been detected in several tissues that are unrelated to calcium metabolism, such as the skin, brain, and breast. The calcium-sensing receptor on cellular level, it regulates cell differentiation, proliferation, cell death, and gene expression. In breast cancer cells, CaSR seems to stimulate secretion of the parathyroid hormone-related protein (PTHrP), which stimulates cellular proliferation. Likewise, some studies have supported not only an association between calcium receptor gene polymorphism and breast cancer risk, but also a higher aggressiveness and unfavorable outcomes in breast cancer, which led us to make a survey in Pubmed on the subject in the last 10 years. Thus, in the literature there is a paucity of studies on the subject and the aim of this review was to show the role of calcium-sensing receptor and its association with breast cancer risk.

Genetic polymorphism of calcium-sensing receptor in women with breast cancer.

Breast cancer is a disease of unknown etiology, whose major risk factors are genetic alterations. Polymorphism of the calcium-sensing receptor (CaSR) has been a focus of some recent studies, due to a probable association with breast cancer risk and tumor aggressiveness. A relationship between polymorphic rs17251221 variant of the CaSR gene, and allele G (considered a gain-of-function mutation) and breast cancer risk has been stressed, despite the paucity of studies found in the literature. The present study involved 137 women (69 women with breast cancer-case; and 68 controls without breast cancer) who had 3 ml of peripheral blood drawn for DNA study. Genomic DNA was extracted from leukocytes by genotyping technique with real-time polymerase chain reaction. The AG genotype (rs17251221) was present in 13 women (18.84%) from the case group and in 8 (11.76%) women from the control group (p = 0.3434), while the GG genotype (rs17251221) did not occur in any group. In contrast, no statistically significant difference was observed between the AG genotype of variant rs17251221 in premenopausal case and control women (p = 0.71). There was also no statistically significant difference between postmenopausal case and control patients (p = 0.6851). In the current study, CaSR gene polymorphism of SNP variant rs17251221 did not show any statistically significant association with breast cancer, in both premenopausal and postmenopausal women.

A comparative study of Ki-67 antigen expression between luminal A and triple-negative subtypes of breast cancer.

Tumor biomarkers such as hormone receptors, HER-2 and Ki-67 are used routinely in clinical practice for classification of molecular subtypes of breast cancer. Cell proliferation evaluated by Ki-67 antigen expression is important to determine tumor aggressiveness. However, there is a paucity of studies comparing Ki-67 expression in an expressive number of cells among molecular subtypes of breast cancer, particularly among less and more aggressive tumors, such as luminal A and triple-negative, which have led us to the present study. The current study included invasive ductal carcinoma samples of 59 patients, which were divided into two groups: luminal A (n = 29) and triple-negative (n = 30). For immunohistochemical reaction, the samples were incubated with monoclonal anti-Ki-67 antibody (clone MIB1) and cells expressing Ki-67 protein were identified by dark brown staining of the nuclei, counting at least 600 cells per slide. The mean percentages of stained nuclei were analyzed by Student's t test (p < 0.05). The mean percentage of nuclei stained with anti-ki-67 was 10.14 and 77.22 in luminal A and triple-negative breast cancers, respectively (p < 0.0001). Our study showed a high cell proliferation of triple-negative breast cancer in comparison with luminal A, justifying its aggressiveness and poor clinical outcome.

Bcl-2 antigen expression in luminal A and triple-negative breast cancer.

Biomarkers for the prognosis of breast cancer have been routinely used in clinical practice, including the expression of hormone receptors, Ki-67 and HER-2. More recently, Bcl-2 has been recognized as an important prognostic factor in breast cancer, although controversies persist with respect to the significance of its expression. The aim of the present study was to evaluate Bcl-2 antigen expression in luminal A and triple-negative breast cancer. Sixty women with invasive ductal carcinoma were included in the study and divided into two groups: Group A (luminal A) and Group B (triple-negative), with 30 cases in each group. Immunohistochemistry was performed on tissue sections to evaluate Bcl-2 antigen expression. Fisher's exact test was used to compare the proportions of cases with cells expressing Bcl-2 between the two subtype cancer groups, with statistical significance being established at p < 0.05. The number of cases with cells expressing Bcl-2 in Groups A and B was 26 (86.7%) and 12 (40.0%), respectively (p < 0.0003). In the present study, the expression of the anti-apoptotic protein Bcl-2 was greater in luminal A breast cancer tissue samples compared to triple-negative breast cancer.

Comparative study between ultrasound-guided fine needle aspiration cytology of axillary lymph nodes and sentinel lymph node histopathology in early-stage breast cancer.

The replacement of sentinel lymph node biopsy (SNB) by ultrasound-guided fine-needle aspiration (US-guided FNA) cytology of axillary lymph nodes is controversial, despite the simplicity and reduced cost of the latter. In the present study, US-guided FNA was performed in 27 patients with early-stage breast cancer for comparison with SNB. Data were analyzed by calculation of sample proportions. Tumor subtypes included invasive ductal carcinoma (85%), invasive lobular carcinoma (7%), and tubular and metaplastic carcinoma (4%). FNA had a sensitivity of 45%, specificity of 100%, positive predictive value of 100% and a negative predictive value of 73%. Axillary lymph node cytology obtained by US guided-FNA in patients with breast cancer had a specificity similar to that of sentinel lymph node histopathology in the presence of axillary node metastases. However, when lymph node cytology is negative, it does not exclude the existence of metastatic implants, due to its low sensitivity in comparison to sentinel lymph node histopathology.

Insulin-like growth factor 1 gene polymorphism in women with breast cancer.

Breast cancer is a disease of unknown etiology; however, the major risk factors are genetic alterations. Studies have demonstrated an association between insulin-like growth factor 1 (IGF-1) gene polymorphism and cell proliferation and reduced apoptosis, in addition to its role in breast cancer growth and aggressiveness. Two polymorphic variants of the IGF-1 gene are highlighted in association with breast cancer, rs6220 and rs7136446, although controversy exists as to this relationship. The current study included 137 women (68 breast cancer cases and 69 controls without breast cancer) who had 3 ml of peripheral blood drawn for the study of genomic DNA extracted from leukocytes using the genotyping technique by real-time polymerase chain reaction. The CC genotype (rs7136446) was present in 4 women (5.9%) from the case group and in 2 (3.0%) women from the control group (p = 0.67), while the GG genotype (rs6220) occurred in 8 (11.5%) women from the case group and in 5 (7.2%) women from the control group (p = 0.75). No statistically significant difference was observed between the CC genotype of variant rs7136446 in premenopausal case and control women (p = 0.31), thus as there was also no significant difference between case and control postmenopausal women (p = 1.00). Concerning the GG genotype of rs6220, it occurred in 6 (14.2%) premenopausal case and 4 (8%) control women (p = 0.71) and no difference was found in postmenopausal women (p = 1.00). In the current study, IGF-1 gene polymorphism of SNP variants rs6220 and rs7136446 had no statistically significant association with breast cancer, both in premenopausal and postmenopausal women.