Plasticity as an Underlying Mechanism of Tumor Heterogeneity in Breast Cancer

Breast cancer shows plasticity in terms of classification. Upon drug treatment and metastasis some tumors switch to another subtype leading to loss of response to therapy. In this study, we ask the question which molecular subclasses of breast cancer are more switchable upon drug therapy and metastasis. We used in silico data to classify breast cancer tumors in PAM50 molecular classes before treatment and after treatment using gene expression data. Similar analysis was performed for primary tumors and their metastatic growth. Our analysis showed that in both scenarios some breast tumors shift from one class to another. This suggests that patients who underwent chemotherapy but resulted in relapse or/and metastasis should be retyped for molecular subclass so that treatment protocol should be adopted according to those subtypes. Additionally, 20 genes were identified as biomarkers for metastasis in breast cancer.

Subtypes of Breast Cancer in Northern India- An Immunohistomolecular Subtypes of Invasive Breast Cancer

Introduction: Breast cancer is a heterogeneous disease that may differ in therapeutic response and prognosis despite similarities in histopathologic types, grade and stage. Molecular studies have identified distinct subtypes of breast carcinoma each having unique recognisable phenotypes and clinical outcomes. Aim: To study the histomorphological features and Immunohistochemical (IHC) profile of breast cancer, to study the distribution of molecular subclass, and to study the morphological features of different molecular subclasses and to determine the association between the pathological features associated with adverse prognosis with the molecular subclass. Materials and Methods: Present study was a prospective cross-sectional observational study based on mastectomy specimens of 122 cases of consecutive cases of invasive breast cancer submitted from June 2012 to February 2014 in Department of Pathology, Institute of Medical Sciences, Banaras Hindu University, Varanasi, Uttar Pradesh, India. On IHC staining with Estrogen Receptors (ER), Progesterone Receptors (PR), Human Epidermal growth factor Receptor 2 (HER2), Cytokeratin (CK5/6) and Epidermal Growth Factor Receptor (EGFR) these cases were classified into Luminal A, Luminal B, HER2 overexpression, basal like and normal breast like molecular subclass. All statistical analysis were performed using Statistical Package for the Social Sciences (SPSS) version 16 (SPSS, Inc., Chicago, IL, USA). Results: The proportion of each subytpes detected in present study were: Luminal A-28.69% (35), Luminal B-17.21% (21), HER2 over expressing-25.41% (31), Basal Like Breast Carcinoma (BLBC)-26.23% (32) and the rest unclassified category (normal breast like)-2.46% (3). The following variables were significantly associated with molecular breast cancer subtypes. The tumours of BLBC and HER2 overexpressing were larger, poorly differentiated, higher mitotic index, more number of positive lymph nodes and with more geographic and central necrosis than Luminal A group. These features were statistically significant (p<0.05). Conclusion: Identification of molecular subtype of breast cancer is extremely important for predicting prognosis and therapeutic response of the breast cancers and thus has role in management of patients of breast cancers. BLBC is a molecular subtype of breast cancer known for its aggressive behaviour and poor prognosis is identified by expression of basal CKs.

Hypermethylator Phenotype and Ectopic GIP Receptor in GNAS Mutation-Negative Somatotropinomas

Context Besides GNAS gene mutations, the molecular pathogenesis of somatotroph adenomas responsible for gigantism and acromegaly remains elusive. Objective To investigate alternative driver events in somatotroph tumorigenesis, focusing on a subgroup of acromegalic patients with a paradoxical increase in growth hormone (GH) secretion after oral glucose, resulting from ectopic glucose-dependent insulinotropic polypeptide receptor (GIPR) expression in their somatotropinomas. Design, Setting, and Patients We performed combined molecular analyses, including array-comparative genomic hybridization, RNA/DNA fluorescence in situ hybridization, and RRBS DNA methylation analysis on 41 somatotropinoma samples from 38 patients with acromegaly and three sporadic giants. Ten patients displayed paradoxical GH responses to oral glucose. Results GIPR expression was detected in 13 samples (32%), including all 10 samples from patients with paradoxical GH responses. All GIPR-expressing somatotropinomas were negative for GNAS mutations. GIPR expression occurred through transcriptional activation of a single allele of the GIPR gene in all GIPR-expressing samples, except in two tetraploid samples, where expression occurred from two alleles per nucleus. In addition to extensive 19q duplications, we detected in four samples GIPR locus microamplifications in a certain proportion of nuclei. We identified an overall hypermethylator phenotype in GIPR-expressing samples compared with GNAS-mutated adenomas. In particular, we observed hypermethylation in the GIPR gene body, likely driving its ectopic expression. Conclusions We describe a distinct molecular subclass of somatotropinomas, clinically revealed by a paradoxical increase of GH to oral glucose related to pituitary GIPR expression. This ectopic GIPR expression occurred through hypomorphic transcriptional activation and is likely driven by GIPR gene microamplifications and DNA methylation abnormalities.