Gene expression signatures: A tool for analysis of breast cancer prognosis and therapy.

Breast Cancer is the most predominant female cancer in developed as well as developing countries. The treatment strategies of breast cancers depends on an array of factors like age at diagnosis, menstrual status, dietary pattern, immunological response, genetic variations of the cancer cells etc. Recent technological advancements in cancer diagnosis lead to the emergence of gene expression pattern for better understanding of the tumor behavior. It has not only bolstered the prognosis, but also the early diagnosis and therapy. The accuracy in disease prognosis can be boosted when gene expression signatures are combined with traditional clinicopathological features. This review explains how the evolution of gene expression signatures for breast cancers, its advantages and future prospects. In addition, an overview of currently available gene expression signature analysis tools and consolidated information on their current status and specific benefits, that can be availed for breast cancer diagnosis are also discussed.

BRCA1 promoter hypermethylation in human placenta: a hidden link with ß-hCG expression.

Gestational trophoblastic diseases (GTD) are group of pregnancy-related tumors characterized by abnormal levels of 'ß-hCG' with higher incidence in South-East Asia, especially India. Our laboratory has reported that wild-type BRCA1 transcriptionally regulates ß-hCG in triple negative breast cancers (TNBCs). These factors culminated into analysis of BRCA1 status in GTD, which would emanate into elucidation of BRCA1- ß-hCG relationship and unraveling etio-pathology of GTD. BRCA1 level in GTD is down-regulated due to the over-expression of DNMT3b and subsequent promoter hypermethylation, when compared to the normal placentae accompanied with its shift in localization. There is an inverse correlation of serum ß-hCG levels with BRCA1 mRNA expression. The effects of methotrexate (MTX), which is the first-line chemotherapeutic used for GTD treatment, when analyzed in comparison with plumbagin (PB) revealed that PB alone is efficient than MTX alone or MTX-PB in combination, in showing selective cytotoxicity against GTD. Interestingly, PB increases BRCA1 levels post-treatment, altering DNMT3b levels and resultant BRCA1 promoter methylation. Also, cohort study analyzed the incidence of GTD at Sree Avittom Thirunal (SAT) Hospital, Thiruvananthapuram, which points out that 11.5% of gestational trophoblastic neoplasia (GTN) cases were referred to Regional Cancer Centre, Thiruvananthapuram, for examination of breast lumps. This has lend clues to supervene the risk of GTD patients towards BRCA1-associated diseases and unveil novel therapeutic for GTD, a plant-derived naphthoquinone, PB, already reported as selectively cytotoxic against BRCA1 defective tumors.

ß-hCG-induced mutant BRCA1 ignites drug resistance in susceptible breast tissue.

ß-hCG expression in breast cancer is highly controversial with reports supporting both protective and tumorigenic effects. It has also been reported that risk of breast cancer at an early age is increased with full-term pregnancies if a woman is a BRCA1 mutation carrier. We have already demonstrated that BRCA1-defective cells express high levels of ß-hCG and that when BRCA1 is restored, ß-hCG level is reduced. Also, BRCA1 can bind to the promoter and reduce the levels of ß-hCG. ß-hCG induces tumorigenicity in BRCA1-defective cells by directly binding to TGFBRII and induces TGFBRII-mediated cell proliferation. In this study, we analyzed the mechanism of action of ß-hCG on BRCA1 expression and its influence on drug sensitivity in breast cancer cells. We demonstrate that ß-hCG induces mutant BRCA1 protein expression in BRCA1 mutant cells; however, in BRCA1 wild-type cells, ß-hCG reduced wild-type BRCA1 protein expression. Transcriptionally, ß-hCG could induce Slug/LSD1-mediated repression of wild-type and mutant BRCA1 messenger RNA levels. However, ß-hCG induces HSP90-mediated stabilization of mutant BRCA1 and hence the overexpression of mutant BRCA1 protein, resulting in partial restoration of homologous recombination repair of damaged DNA. This contributes to drug resistance to HSP90 inhibitor 17AAG in BRCA1-defective cancer cells. A combination of HSP90 inhibitor and TGFBRII inhibitor has shown to sensitize ß-hCG expressing BRCA1-defective breast cancers to cell death. Targeting the ß-hCG-HSP90-TGFBRII axis could prove an effective treatment strategy for BRCA1-mutated breast tumors.

Detection and characterization of an albumin-like protein in Leishmania donovani.

The protozoan parasite, Leishmania donovani, undergoes several molecular adaptations and secretes many effector molecules for host cell manipulation and successful parasitism. The current study identifies an albumin-like secretory protein, expressed in its extracellular promastigote forms. A leishmanial complementary DNA sequence of a partial gene has been cloned, and the encoded peptide (14 kD) is used for the production of polyclonal antibody. This targeted antibody identifies a large native protein (66.421 kD), expressed stage-specifically in promastigotes. Through electron microscopic studies, the native protein is found to be localized in the flagellar pocket and flagella and at the surface of the promastigotes. This native protein is purified with the same customized antibody for future characterization and sequencing. The sequence analysis reveals its homology with the mammalian serum albumin. It is evidenced from in silico studies that this albumin-like protein remains associated with long-chain fatty acids while in vitro studies indicate its close association with membrane cholesterol. Since antibody-mediated blocking compromises the parasite infectivity, these leishmanial albumin-like molecules are hereby proposed to play an instrumental role in the infectivity of L. donovani to peripheral blood monocyte cells. Thus, identification and characterization of an albumin-like protein in L. donovani promastigotes may be interpreted as a molecular adaptation candidate. It may be hypothesized that the parasite mimics the mammalian system for importing fatty acids into the intracellular amastigotes, facilitating its host cell infectivity.

Brcal Defective Breast Cancer Cells Induce in vitro Transformation of Cancer Associated Fibroblasts (CAFs) to Metastasis Associated Fibroblasts (MAF).

It is known that Cancer Associated Fibroblast (CAFs) from the primary tumor site can accompany cancer cells to a secondary site during the process of metastasis. We hypothesize that these CAFs could be transformed to an altered cell type, which can be called as Metastasis Associated Fibroblasts (MAF) in turn can support, and convoy cancer cells for metastasis. There are no published reports that have characterized and distinguished CAFs from MAF. It is well established that some of the cancer cells within the tumor mass accumulate novel mutations prior to metastasis. Hence, we speculated that mutations in the tumor suppressor gene, BRCA1, which is already reported to induce metastasis via abnormal expression of Ezrin, Radixin and Moesin (ERM), could generate MAF. In the present study, we demonstrate for the first time that CAFs isolated from primary breast cancer tissues when co-cultured with BRCA1 mutated HCC1937 cells transform CAFs to MAF in vitro. As expected, MAF augmented proliferation, migration and invasion along with over-expression of epithelial mesenchymal transition (EMT) markers, Ezrin and CCL5, thereby facilitating metastasis. Therefore, we inhibited Ezrin and CCL5 in vitro in MAF and observed that the migration and invasion abilities of these cells were attenuated. This highlights the intriguing possibilities of combination therapy using MAF inhibitors as anti-metastatic agents along with anticancer drugs, to control the metastatic spread from primary tumor site.

Regulation of epithelial to mesenchymal transition by BRCA1 in breast cancer.

Reports till its discovery has proven multiple facets of Breast Cancer type 1 susceptibility gene (BRCA1) from nucleus to cytoplasm; from DNA repair to drug resistance; from Homologous Recombination (HR) to Ubiquitination; from breast to brain; from cancer to HIV and many of the roles are still unexplored. One of the recent attractions of BRCA1 is its role in regulating breast cancer metastasis though the exact mechanism is poorly understood. In this review, we will discuss the molecular interactions between BRCA1 and the key molecules of Epithelial to Mesenchymal Transition (EMT) associated with metastasis, its associated drug resistance and the possible treatment strategy for BRCA1 mutated breast cancer.

Proteomic Profiling of ß-hCG-Induced Spheres in BRCA1 Defective Triple Negative Breast Cancer Cells.

Previously, we identified that ß-hCG is expressed by BRCA1 mutated but not wild type breast cancers in vitro/in vivo and exhibited a novel event in ß-hCG overexpressing BRCA1 mutated HCC1937 cells where the cells were able to form spheres (HCC1937 ß spheres) in adherent cell culture plates even in the absence of any growth factors. These spheres express stem cell and EMT markers. In the present study, we carried out the total proteomic profiling of these HCC1937 ß spheres obtained from BRCA1 defective ß-hCG expressing stable breast cancer cells to analyze the cell signaling pathways that are active in these cells. Functional annotation revealed proteins (164 cellular and 97 secretory) predominantly involved in oxygen binding, nucleosome assembly, cytoskeleton organization, protein folding, etc. Many of the proteins identified from HCC1937 ß spheres in this study are also up regulated in breast cancers, which are directly linked with poor prognosis in human cancer samples as analyzed using TCGA data set. Survival analysis shows that ß-hCG expressing cancer patients are linked with poor survival rate. Interestingly, hemoglobins were identified at both cellular and secretory level in HCC1937 ß spheres and experiments after treating with ROS inducers revealed that ß-hCG induces hemoglobin and protects the cancer cells during oxidative stress. Our proteomic data strongly propose ß-hCG as an oncogenic molecule associated with BRCA1 mutation, and hence, targeting ß-hCG could be a strategy to treat BRCA1 defective breast cancers.

The prodigious network of chromosome 17 miRNAs regulating cancer genes that influence the hallmarks of cancer.

Chromosome 17 (Chr17) harbors crucial genes that encode proteins implicated in a variety of cancers, including some that guard cancer cells from genomic instability and others that interfere with metastasis. Included amongst the genes on chr17 that regulate biological processes fundamental to the genesis of cancer are TP53, BRCA1, CCL5, NF-1, and GRB7. As many as 50% of all human tumors and at least 30% of breast carcinomas contain p53 mutations, while 30%-40% of breast cancers have defective BRCA1. A large number of proteins regulate the expression of these cancer genes on chr17 with miRNAs, the most widely studied class of regulatory RNAs, playing a major role in epigenetically controlling the gene expression programs, thereby managing various cellular functions. This review provides information on the genes transcribed from chr17, and their regulation by miRNAs in the context to tumorigenesis located on chr17, along with an analysis of the receptor status (estrogen, progesterone, and Her2/Neu) from the miRNA prediction data of miRNA genes located on chr17.

Increased sensitivity of BRCA defective triple negative breast tumors to plumbagin through induction of DNA Double Strand Breaks (DSB).

We have earlier shown that Plumbagin (PB) can induce selective cytotoxicity to BRCA1 defective ovarian cancer cells; however, the effect of this molecule in BRCA1 mutated breast cancers has not been analyzed yet. Here, we report that reactive oxygen species (ROS) induced by PB resulted in DNA DSB and activates downstream signaling by ATR/ATM kinases and subsequent apoptosis. PB reduces DNA- dependent protein kinase (DNA-PK) expression and inhibits NHEJ (Non Homologous End Joining) activity in BRCA1 defective breast cancer cells. Also, PB induces apoptosis in two different BRCA1 conditional knock out murine models: MMTV-Cre; BRCA1(Co/Co) and WAP-Cre; BRCA1(Co/Co), at 2 mg/kg body weight, but 32 mg/kg of carboplatin (CN) was needed to induce apoptosis in them. This is the first study where two different tissue specific promoter driven transgenic mice models with BRCA1 exon 11 deletions are used for preclinical drug testing. The apoptosis induced by PB in HR (Homologous Recombination) defective triple negative BRCA1 mutant cell lines and in mouse models occur by inducing ROS mediated DNA DSB. The toxicity profile as compared with CN in transgenic mice provides evidence for PB's safer disposition as a therapeutic lead in breast cancer drug development.