Mahendra Singh

Publications

• 7.54

  Impact points

  Enhanced genetic instability and dasatinib sensitivity in mammary tumor cells lacking NEDD9.

  Mahendra K Singh, Eugene Izumchenko, Andres J Klein-Szanto, Brian L Egleston, Marina Wolfson, Erica A Golemis

  Cancer research. 10/2010; 70(21):8907-16.

  Elevated expression of the NEDD9/HEF1/Cas-L scaffolding protein promotes tumor cell invasion and metastasis in multiple cancer cell types. Conversely, generation of mammary tumors in the mouse mammary tumor virus (MMTV)-polyoma virus middle T (PyVT) genetic model is delayed by a Nedd9(-/-) genotype.... [more] Elevated expression of the NEDD9/HEF1/Cas-L scaffolding protein promotes tumor cell invasion and metastasis in multiple cancer cell types. Conversely, generation of mammary tumors in the mouse mammary tumor virus (MMTV)-polyoma virus middle T (PyVT) genetic model is delayed by a Nedd9(-/-) genotype. These activities arise from the role of NEDD9 in assembling complexes and supporting activity of cancer signaling proteins, including FAK, Src, Shc, and AKT, and would support evaluation of NEDD9 expression as an unambiguous biomarker for tumor aggressiveness. However, we here show that despite the initial delay in tumor growth, cells derived from MMTV-PyVT;Nedd9(-/-) tumors are characteristically hyperaggressive versus MMTV-PyVT;Nedd9(+/+) cells in anchorage-independent growth, in growth on three-dimensional matrix produced by tumor-associated fibroblasts, and in formation of tumors after mammary orthotopic reinjection and of lung metastases after tail vein injection. This reversal suggests the specific selection of MMTV-PyVT;Nedd9(-/-) cells for growth in an in vivo microenvironment. Indeed, MMTV-PyVT;Nedd9(-/-) cells have increased cell cycle, centrosomal, and mitotic defects, phenotypes compatible with the increased selection of these cells for aggressive growth. Intriguingly, in spite of their aggressive phenotype, MMTV-PyVT;Nedd9(-/-) cells persistently have low levels of Src activation and are hypersensitive to the Src kinase inhibitor dasatinib. These studies identify NEDD9 as a complex modulator of different aspects of mammary tumor growth.

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• 7.54

  Impact points

  NEDD9 Promotes Oncogenic Signaling in Mammary Tumor Development.

  Eugene Izumchenko, Mahendra K Singh, Olga V Plotnikova, Nadezhda Tikhmyanova, Joy L Little, Ilya G Serebriiskii, Sachiko Seo, Mineo Kurokawa, Brian L Egleston, Andres Klein-Szanto, Elena N Pugacheva, Richard R Hardy, Marina Wolfson, Denise C Connolly, Erica A Golemis

  Cancer research. 10/2009;

  In the past 3 years, altered expression of the HEF1/CAS-L/NEDD9 scaffolding protein has emerged as contributing to cancer metastasis in multiple cancer types. However, whereas some studies have identified elevated NEDD9 expression as prometastatic, other work has suggested a negative role in tumor p... [more] In the past 3 years, altered expression of the HEF1/CAS-L/NEDD9 scaffolding protein has emerged as contributing to cancer metastasis in multiple cancer types. However, whereas some studies have identified elevated NEDD9 expression as prometastatic, other work has suggested a negative role in tumor progression. We here show that the Nedd9-null genetic background significantly limits mammary tumor initiation in the MMTV-polyoma virus middle T genetic model. Action of NEDD9 is tumor cell intrinsic, with immune cell infiltration, stroma, and angiogenesis unaffected. The majority of the late-appearing mammary tumors of MMTV-polyoma virus middle T;Nedd9(-/-) mice are characterized by depressed activation of proteins including AKT, Src, FAK, and extracellular signal-regulated kinase, emphasizing an important role of NEDD9 as a scaffolding protein for these prooncogenic proteins. Analysis of cells derived from primary Nedd9(+/+) and Nedd9(-/-) tumors showed persistently reduced FAK activation, attachment, and migration, consistent with a role for NEDD9 activation of FAK in promoting tumor aggressiveness. This study provides the first in vivo evidence of a role for NEDD9 in breast cancer progression and suggests that NEDD9 expression may provide a biomarker for tumor aggressiveness. [Cancer Res 2009;69(18):7198-206].
• 5.98

  Impact points

  A Novel Cas Family Member, HEPL, Regulates FAK and Cell Spreading.

  Mahendra K Singh, Disha Dadke, Emmanuelle Nicolas, Ilya G Serebriiskii, Sinoula Apostolou, Adrian Canutescu, Brian L Egleston, Erica A Golemis

  Molecular biology of the cell. 05/2008; 19(4):1627-36.

  For over a decade, p130Cas/BCAR1, HEF1/NEDD9/Cas-L, and Efs/Sin have defined the Cas (Crk-associated substrate) scaffolding protein family. Cas proteins mediate integrin-dependent signals at focal adhesions, regulating cell invasion and survival; at least one family member, HEF1, regulates mitosis. ... [more] For over a decade, p130Cas/BCAR1, HEF1/NEDD9/Cas-L, and Efs/Sin have defined the Cas (Crk-associated substrate) scaffolding protein family. Cas proteins mediate integrin-dependent signals at focal adhesions, regulating cell invasion and survival; at least one family member, HEF1, regulates mitosis. We here report a previously undescribed novel branch of the Cas protein family, designated HEPL (for HEF1-Efs-p130Cas-like). The HEPL branch is evolutionarily conserved through jawed vertebrates, and HEPL is found in some species lacking other members of the Cas family. The human HEPL mRNA and protein are selectively expressed in specific primary tissues and cancer cell lines, and HEPL maintains Cas family function in localization to focal adhesions, as well as regulation of FAK activity, focal adhesion integrity, and cell spreading. It has recently been demonstrated that upregulation of HEF1 expression marks and induces metastasis, whereas high endogenous levels of p130Cas are associated with poor prognosis in breast cancer, emphasizing the clinical relevance of Cas proteins. Better understanding of the complete protein family should help inform prediction of cancer incidence and prognosis.
• 3.34

  Impact points

  Molecular basis for HEF1/NEDD9/Cas-L action as a multifunctional co-ordinator of invasion, apoptosis and cell cycle.

  Mahendra Singh, Lauren Cowell, Sachiko Seo, Geraldine O'neill, Erica Golemis

  Cell biochemistry and biophysics. 02/2007; 48(1):54-72.

  Upregulation of the scaffolding protein HEF1, also known as NEDD9 and Cas-L, has recently been identified as a pro-metastatic stimulus in a number of different solid tumors, and has also been strongly associated with pathogenesis of BCR-Abl-dependent tumors. As the evidence mounts for HEF1/NEDD9/Cas... [more] Upregulation of the scaffolding protein HEF1, also known as NEDD9 and Cas-L, has recently been identified as a pro-metastatic stimulus in a number of different solid tumors, and has also been strongly associated with pathogenesis of BCR-Abl-dependent tumors. As the evidence mounts for HEF1/NEDD9/Cas-L as a key player in metastatic cancer, it is timely to review the molecular regulation of HEF1/NEDD9/Cas-L. Most of the mortality associated with cancer arises from uncontrolled metastases, thus a better understanding of the properties of proteins specifically associated with promotion of this process may yield insights that improve cancer diagnosis and treatment. In this review, we summarize the extensive literature regarding HEF1/NEDD9/Cas-L expression and function in signaling relevant to cell attachment, migration, invasion, cell cycle, apoptosis, and oncogenic signal transduction. The complex function of HEF1/NEDD9/Cas-L revealed by this analysis leads us to propose a model in which alleviation of cell cycle checkpoints and acquired resistance to apoptosis is permissive for a HEF1/NEDD9/Cas-L-promoted pro-metastatic phenotype.
• 5.98

  Impact points

  Deregulation of HEF1 impairs M-phase progression by disrupting the RhoA activation cycle.

  Disha Dadke, Michael Jarnik, Elena N Pugacheva, Mahendra K Singh, Erica A Golemis

  Molecular biology of the cell. 04/2006; 17(3):1204-17.

  The focal adhesion-associated signaling protein HEF1 undergoes a striking relocalization to the spindle at mitosis, but a function for HEF1 in mitotic signaling has not been demonstrated. We here report that overexpression of HEF1 leads to failure of cells to progress through cytokinesis, whereas de... [more] The focal adhesion-associated signaling protein HEF1 undergoes a striking relocalization to the spindle at mitosis, but a function for HEF1 in mitotic signaling has not been demonstrated. We here report that overexpression of HEF1 leads to failure of cells to progress through cytokinesis, whereas depletion of HEF1 by small interfering RNA (siRNA) leads to defects earlier in M phase before cleavage furrow formation. These defects can be explained mechanistically by our determination that HEF1 regulates the activation cycle of RhoA. Inactivation of RhoA has long been known to be required for cytokinesis, whereas it has recently been determined that activation of RhoA at the entry to M phase is required for cellular rounding. We find that increased HEF1 sustains RhoA activation, whereas depleted HEF1 by siRNA reduces RhoA activation. Furthermore, we demonstrate that chemical inhibition of RhoA is sufficient to reverse HEF1-dependent cellular arrest at cytokinesis. Finally, we demonstrate that HEF1 associates with the RhoA-GTP exchange factor ECT2, an orthologue of the Drosophila cytokinetic regulator Pebble, providing a direct means for HEF1 control of RhoA. We conclude that HEF1 is a novel component of the cell division control machinery and that HEF1 activity impacts division as well as cell attachment signaling events.

• Total PSA and free PSA in patients with severe liver dysfunction

  Rama Mittal, Mahendra Singh, Charles Selvaraju, Gourdas Choudhuri

  Indian Journal of Urology. 01/2003;

  Objectives: To evaluate the effect of liver diseases in patients, on serum free prostate specific antigen (JPSA) levels, total prostate specific antigen (tPSA) levels and fPSA/tPSA ratios. Methods: Serum concentrations of total and free as well as JPSA/tPSA were determined in 20 men with histologi-c... [more] Objectives: To evaluate the effect of liver diseases in patients, on serum free prostate specific antigen (JPSA) levels, total prostate specific antigen (tPSA) levels and fPSA/tPSA ratios. Methods: Serum concentrations of total and free as well as JPSA/tPSA were determined in 20 men with histologi-cally confirmed liver cirrhosis, 15 men with chronic hepa-titis and 20 healthy men. Results: The serum levels of total PSA in liver cirrhosis as well as in chronic hepatitis were significantly lower than those observed in control. Free PSA remained unchanged. Conclusions: Our study suggests that despite severe liver dysfunction the tPSA, fPSA as well as the ratio of fPSA/ tPSA were not elevated as it was hypothesized that liver impairment might affect the PSA levels, as liver is a site for PSA metabolism.