Gap junction ß­2 expression is negatively associated with the estrogen receptor status in breast cancer tissues and is a regulator of breast tumorigenesis.

Gap junction ß­2 gene (GJB2, also known as connexin 26) is a member of the connexin family which forms gap junction channels. Many connexin genes have been considered to be tumor suppressor genes. However, the overexpression of GJB2 has been found to be associated with a poor prognosis in several human cancers. In our previous microarray study, we revealed the overexpression of GJB2 in breast cancer tissues. Hence, in this study, we investigated the expression of GJB2 in human breast cancer and its role in breast cancer cell proliferation and migration. The RT­qPCR results revealed the upregulation of the GJB2 gene in invasive ductal carcinoma (P<0.001) of the breast. Immunohistochemical analysis revealed an intense cytoplasmic and membrane staining. We observed that the staining for GJB2 was more intense in the majority of the estrogen receptor (ER)­negative breast cancer tissues compared to the normal breast tissues (P<0.0001). By contrast, the majority of the ER­positive breast cancer samples exhibited weak to moderate staining; however, this difference was not statistically significant compared to the normal tisues. The knockdown of GJB2 in human breast cancer cell lines using shRNA led to a significant decrease in the proliferative ability and an increase in the migratory ability of breast cancer cells. In addition, the knockdown of GJB­2 led to a significant reduction in tumor volume and proliferation (as demonstrated by MIB­1 staining) in orthotopic xenografts in immunocompromised mice. On the whole, the findings of this study indicate that GJB2 may be an important regulator of breast tumorigenesis.

Expression of tripartite motif-containing protein 28 in primary breast carcinoma predicts metastasis and is involved in the stemness, chemoresistance, and tumor growth.

The prediction of who develops metastasis has been the most difficult aspect in the management of breast cancer patients. The lymph node metastasis has been the most useful predictor of prognosis and patient management. However, a good proportion of patients with lymph node positivity remain disease free for 5 years or more, while about a third of those who were lymph node negative develop distant metastasis within the same period. This warrants a robust biomarker(s), preferably gene expression based. In order to elucidate gene-based biomarkers for prognosis of breast cancers, gene expression profiling of primary tumors and follow-up for over 5 years has been performed. The analysis revealed a network of genes centered around the tripartite motif-containing protein 28 as an important indicator of disease progression. Short hairpin RNA-mediated knockdown of tripartite motif-containing protein 28 in breast cancer cells revealed a decreased expression of epithelial-to-mesenchymal transition markers and increased expression of epithelial markers, decreased migration and invasion, and increased chemosensitivity to doxorubicin, 5-fluorouracil, and methotrexate. Furthermore, knockdown of tripartite motif-containing protein 28 resulted in the decrease of stemness as revealed by sphere formation assay as well as decreased expression of CD44 and Bmi1. Moreover, tripartite motif-containing protein 28 knockdown significantly reduced the tumor size and lung metastasis in orthotopic tumor xenograft assay in immunocompromised mice. The tumor size was further reduced when these mice were treated with doxorubicin. These data provide evidence for tripartite motif-containing protein 28 as a biomarker and a potential therapeutic target for breast cancer.

Activin-A signaling promotes epithelial-mesenchymal transition, invasion, and metastatic growth of breast cancer.

BACKGROUND: Activins belong to the transforming growth factor-ß (TGF-ß) superfamily of cytokines. Although the role of TGF-ß in cancer progression has been highly advocated, the role of activin signaling in cancer is not well known. However, overexpression of activin-A has been observed in several cancers. AIMS: The gene expression profile indicated higher expression of Activin-A in breast tumors. Hence the aim of this study was to evaluate the status and role of Activin signaling pathway in these tumors. METHODS: Microarray analysis was performed to reveal gene expression changes in breast tumors. The results were validated by quantitative PCR and immunohistochemical analysis in two independent sets of normal and tumor samples. Further, correlation of activin expression with survival and distant metastasis was performed to evaluate its possible role in tumor progression. We used recombinant activin-A, inhibitors, overexpression, and knockdown strategies both in vitro and in vivo, to understand the mechanism underlying the protumorigenic role of this signaling pathway. RESULTS: We report that activin-A signaling is hyperactivated in breast cancers as indicated by higher activin-A, phosphoSMAD2, and phosphoSMAD3 levels in advanced breast cancers. Bone morphogenetic proteins and molecules involved in this signaling pathway were downregulated, suggesting its suppression in breast cancers. Activin-A expression correlates inversely with survival and metastasis in advanced breast cancers. Further, activin-A promotes anchorage-independent growth, epithelial-mesenchymal transition, invasion, angiogenesis, and stemness of breast cancer cells. We show that activin-A-induced phenotype is mediated by SMAD signaling pathway. In addition, activin-A expression affects the tumor-forming ability and metastatic colonization of cancer cells in nude mice. CONCLUSIONS: These results suggest that activin-A has a critical role in breast cancer progression and, hence, targeting this pathway can be a valuable strategy in treating breast cancer patients.

Rrp1B gene polymorphism (1307T>C) in metastatic progression of breast cancer.

Rrp1B (ribosomal RNA processing1 homolog B) is a novel candidate metastasis modifier gene in breast cancer. Functional gene assays demonstrated that a physical and functional interaction existing between Rrp1b and metastasis modifier gene SIPA1 causes reduction in the tumor growth and metastatic potential. Ectopic expression of Rrp1B modulates various metastasis predictive extra cellular matrix (ECM) genes associated with tumor suppression. The aim of this study is to determine the functional significance of single nucleotide polymorphism (SNP) in human Rrp1B gene (1307 T>C; rs9306160) with breast cancer development and progression. The study consists of 493 breast cancer cases recruited from Nizam's Institute of Medical Sciences, Hyderabad, and 558 age-matched healthy female controls from rural and urban areas. Genomic DNA was isolated by non-enzymatic method. Genotyping was done by amplification refractory mutation system (ARMS-PCR) method. Genotypes were reconfirmed by sequencing and results were analyzed statistically. We have performed Insilco analysis to know the RNA secondary structure by using online tool m fold. The TT genotype and T allele frequencies of Rrp1B1307 T>C polymorphism were significantly elevated in breast cancer (χ (2); p = <0.008) cases compared to controls under different genetic models. The presence of T allele had conferred 1.75-fold risk for breast cancer development (OR = 1.75; 95% CI = 1.15-2.67). The frequency of TT genotype of Rrp1b 1307T>C polymorphism was significantly elevated in obese patients (χ (2); p = 0.008) and patients with advanced disease (χ (2); p = 0.01) and with increased tumor size (χ (2); p = 0.01). Moreover, elevated frequency of T allele was also associated with positive lymph node status (χ (2); p = 0.04) and Her2 negative receptor status (χ (2); p = 0.006). Presence of Rrp1b1307TT genotype and T allele confer strong risk for breast cancer development and progression.

HIF-1α (1772C>T) polymorphism as marker for breast cancer development.

Hypoxia-inducible factor 1α (HIF-1α) is an important transcription factor that regulates different cellular responses to hypoxia. HIF-1α is rapidly degraded by von Hippel-Lindau (VHL) protein under normoxic conditions and stabilized under hypoxia. A common variant of HIF-1α (1772C>T) (rs 11549465) polymorphism, corresponding to an amino acid change from proline to serine at 582 position within the oxygen-dependent degradation domain, results in increased stability of the protein and altered transactivation of its target genes. The present study was aimed to find the association between HIF-1α (1772C>T) (rs 11549465) polymorphism and breast cancer development. For this purpose, 348 primary breast cancer patients and 320 healthy and age-matched controls were genotyped through PCR-RFLP method. The genotype frequencies were compared between patients and controls, and their influence on clinical characteristics of breast cancer patients was analyzed. Our study revealed a significant increase of TT genotype in breast cancer patients compared to controls (p = 0.038). Further, TT genotype and T allele were found to be associated with progesterone receptor (PR)-negative status (p < 0.09). None of the clinical variables revealed significant association with HIF-1α (1772C>T) (rs 11549465) polymorphism.

Germline mutations of TP53 gene in breast cancer.

Germline alterations of the TP53 gene encoding the p53 protein have been observed in the majority of families with the Li-Fraumeni syndrome, a rare dominantly inherited disorder with breast cancer. Genomic DNA samples of 182 breast cancer cases and 186 controls were sequenced for TP53 mutations in the exon 5-9 and intervening introns 5, 7-9. Direct sequencing was done using Applied Biosystem 3730 DNA analyzer. In the present study, we observed nine mutations in the sequenced region, of which five were novel. Hardy-Weinberg equilibrium (HWE) was done for all the mutations; C14181T, T14201G, and G13203A have shown deviation from HWE. High linkage disequilibrium (LD) was observed between C14181T (rs129547788) and T14201G (rs12951053) (r (2) = 0.98.3; D' = 1.00), whereas other observed mutations do not show strong LD with any of the other mutations. None of the intronic mutations has shown significant association with the breast cancer, two exonic mutations G13203A (rs28934578) and A14572G are significantly (P = 0.04, P = 0.007) associated with breast cancer. Germline mutations observed in DNA-binding domain of the gene showed significant association with breast cancer. This study reports five novel germline mutations in the TP53 gene out of which one mutation may confer significant risk to the breast cancer. Mutations in DNA-binding domain of TP53 gene may play role in the early onset and prognosis of breast cancer. The population-based studies of germline mutations in DNA-binding domain of TP53 gene helps in identification of individuals and families who are at risk of developing cancers.

Fms like tyrosine kinase (FLT3) and nucleophosmin 1 (NPM1) mutations in de novo normal karyotype acute myeloid leukemia (AML).

Mutations in FLT3 and NPM1 are important prognostic factors in AML, influencing outcome in normal karyotype cases. We here analysed incidences of FLT3/ITD, D 835 and NPM1 mutations in patients with de novo normal karyotype AML using PCR and gene sequencing, along with laboratory parameters and treatment outcomes. There were 128 patients with a median age of 45 years (range, 19-65). FLT3/ITD mutations were detected in 26 (20.3%), FLT3/D835 in 8 (6.2%) and NPM1 in 22 (17.1%). The incidence of FLT3/ITD was higher in those with elevated lactate dehydrogenase (LDH) and peripheral blasts (p=< 0.002, < 0.001) while NPM1 mutations or both NPM1 and FLT3/ITD was more common in elevated total leukocyte counts (TLC), LDH and peripheral blasts (p=<0.0001). Complete response and disease free survival were lower in those with FLT3/ITD mutations (p=0.04, 0.03). The incidence of FLT3 and NPM1 mutations was found to be low in Indian patients with normal karyotype AML.