Showing papers by "Suresh K. Alahari published in 2013"

Prooncogenic Factors miR-23b and miR-27b Are Regulated by Her2/Neu, EGF, and TNF-α in Breast Cancer

Abstract: MicroRNAs (miRs) are a critical class of small (21–25 nucleotides) non-coding endogenous RNAs implicated in gene expression regulation. We identified miR-23b and miR-27b as miRNAs that are highly upregulated in human breast cancer. We found that engineered knockdown of miR-23b and miR-27b substantially repressed breast cancer growth. Nischarin (NISCH) expression was augmented by knockdown of miR-23b as well as miR-27b. Notably, these miRNAs and Nischarin were inversely expressed in human breast cancers, underscoring their biologic relevance. We demonstrated the clinical relevance of the expression of these miRNAs and showed that high expression of miR-23b and miR-27b correlates with poor outcome in breast cancer. Moreover, intraperitoneally delivered anti-miR-27b restored Nischarin expression and decreased tumor burden in a mouse xenograft model of human mammary tumor. Also we report for the first time that HER2/neu (ERBB2), EGF, and TNFA promote miR-23b/27b expression through the AKT/NF-κB signaling cascade. Nischarin was found to regulate miR-27b/23b expression through a feedback loop mechanism by suppressing NF-κB phosphorylation. Since anti-miR-27b compounds that suppress miR-27b inhibit tumor growth, the anti-miR-27b appears to be a good candidate for the development of new anti-tumor therapies.

PDZK1 Is a Novel Factor in Breast Cancer That Is Indirectly Regulated by Estrogen through IGF-1R and Promotes Estrogen-Mediated Growth

Abstract: Although a relationship between PDZK1 expression and estrogen receptor (ER)-α stimulation has been suggested, the nature of such a connection and the function of PDZK1 in breast cancer remain unknown. Human tissue microarrays (cancer tissue: 262 cores; normal tissue: 87 cores) and breast cancer cell lines were used to conduct the study. We show that PDZK1 protein expression is tightly correlated with human breast malignancy, is negatively correlated with age and had no significant correlation with ER-α expression levels. PDZK1 exhibited an exclusive epithelial expression with mostly cytosolic subcellular localization. Additionally, 17β-estradiol induced PDZK1 expression above its basal level more than 24 h after treatment in MCF-7 cells. PDZK1 expression was indirectly regulated by ER-α stimulation, requiring insulinlike growth factor 1 receptor (IGF-1R) expression and function. The molecular link between PDZK1 and IGF-1R was supported by a significant correlation between protein and mRNA levels (r = 0.591, p < 0.001, and r = 0.537, p < 0.001, respectively) of the two factors in two different cohorts of human breast cancer tissues. Interestingly, PDZK1 knockdown in MCF-7 cells blocked ER-dependent growth and reduced c-Myc expression, whereas ectopic expression of PDZK1 enhanced cell proliferation in the presence or absence of 17β-estradiol potentially through an increase in c-Myc expression, suggesting that PDZK1 has oncogenic activity. PDKZ1 also appeared to interact with the Src/ER-α/epidermal growth factor receptor (EGFR) complex, but not with IGF-1R and enhanced EGFR-stimulated MEK/ERK1/2 signaling. Collectively, our results clarify the relationship between ER-α and PDZK1, propose a direct relationship between PDZK1 and IGF-1R, and identify a novel oncogenic activity for PDZK1 in breast cancer.

Rac and Rab GTPases dual effector Nischarin regulates vesicle maturation to facilitate survival of intracellular bacteria.

Abstract: The intracellular pathogenic bacterium Salmonella enterica serovar typhimurium (Salmonella) relies on acidification of the Salmonella-containing vacuole (SCV) for survival inside host cells. The transport and fusion of membrane-bound compartments in a cell is regulated by small GTPases, including Rac and members of the Rab GTPase family, and their effector proteins. However, the role of these components in survival of intracellular pathogens is not completely understood. Here, we identify Nischarin as a novel dual effector that can interact with members of Rac and Rab GTPase (Rab4, Rab14 and Rab9) families at different endosomal compartments. Nischarin interacts with GTP-bound Rab14 and PI(3)P to direct the maturation of early endosomes to Rab9/CD63-containing late endosomes. Nischarin is recruited to the SCV in a Rab14-dependent manner and enhances acidification of the SCV. Depletion of Nischarin or the Nischarin binding partners—Rac1, Rab14 and Rab9 GTPases—reduced the intracellular growth of Salmonella. Thus, interaction of Nischarin with GTPases may regulate maturation and subsequent acidification of vacuoles produced after phagocytosis of pathogens.

MicroRNA in cancer

Abstract: Preface. Chapter 1: MicroRNAs and other non-coding RNAs: Implications for cancer patients. Chapter 2: Function of miRNAs in tumor cell proliferation. Chapter 3: MicroRNAs in cancer Stem cells. Chapter 4: MicroRNAs in the pathogenesis of viral infection and cancer. Chapter 5: Oncogenic microRNAs. Chapter 6: regulation of metastasis by miRNAs. Chapter 7: MicroRNAs in Leukemias. Chapter 8: Small Molecule regulation of microRNA function. Index.

Regulation of Metastasis by miRNAs

Abstract: A breakthrough of the twenty-first century is the discovery in which protein expression is regulated by a new class of endogenous, noncoding, small RNAs (microRNAs). These microRNAs (miRNAs) control gene expression by acting on their target mRNAs, inducing either mRNA degradation or translational repression. MiRNAs are single-stranded and highly conserved between species. MiRNAs have been implicated in the detection and treatment of various pathological states. In the genome, most miRNAs are much smaller than protein coding genes, but they have specific functions in various biological processes. The major process in cancer progression is metastasis. Metastatic processes include invasion, intravasation, and extravasation. In this chapter, we introduce basic information about miRNAs, their functional mechanism, and their biological roles in tumor metastasis.