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  1. Article ; Online: Intercellular redistribution of cAMP underlies selective suppression of cancer cell growth by connexin26.

    Anjana Chandrasekhar / Edward A Kalmykov / Srikanth R Polusani / Sandra A Mathis / Shoshanna N Zucker / Bruce J Nicholson

    PLoS ONE, Vol 8, Iss 12, p e

    2013  Volume 82335

    Abstract: Connexins (Cx), which constitute gap junction intercellular channels in vertebrates, have been shown to suppress transformed cell growth and tumorigenesis, but the mechanism(s) still remain largely speculative. Here, we define the molecular basis by ... ...

    Abstract Connexins (Cx), which constitute gap junction intercellular channels in vertebrates, have been shown to suppress transformed cell growth and tumorigenesis, but the mechanism(s) still remain largely speculative. Here, we define the molecular basis by which Cx26, but less frequently Cx43 or Cx32, selectively confer growth suppression on cancer cells. Functional intercellular coupling is shown to be required, producing partial blocks of the cell cycle due to prolonged activation of several mitogenic kinases. PKA is both necessary and sufficient for the Cx26 induced growth inhibition in low serum and the absence of anchorage. Activation of PKA was not associated with elevated cAMP levels, but appeared to result from a redistribution of cAMP throughout the cell population, eliminating the cell cycle oscillations in cAMP required for efficient cell cycle progression. Cx43 and Cx32 fail to mediate this redistribution as, unlike Cx26, these channels are closed during the G2/M phase of the cell cycle when cAMP levels peak. Comparisons of tumor cell lines indicate that this is a general pattern, with growth suppression by connexins occurring whenever cAMP oscillates with the cell cycle, and the gap junction remain open throughout the cell cycle. Thus, gap junctional coupling, in the absence of any external signals, provides a general means to limit the mitotic rate of cell populations.
    Keywords Medicine ; R ; Science ; Q
    Subject code 571
    Language English
    Publishing date 2013-01-01T00:00:00Z
    Publisher Public Library of Science (PLoS)
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  2. Article ; Online: A Purine Nucleotide Biosynthesis Enzyme Guanosine Monophosphate Reductase Is a Suppressor of Melanoma Invasion

    Joseph A. Wawrzyniak / Anna Bianchi-Smiraglia / Wiam Bshara / Sudha Mannava / Jeff Ackroyd / Archis Bagati / Angela R. Omilian / Michael Im / Natalia Fedtsova / Jeffrey C. Miecznikowski / Kalyana C. Moparthy / Shoshanna N. Zucker / Qianqian Zhu / Nadezhda I. Kozlova / Albert E. Berman / Keith S. Hoek / Andrei V. Gudkov / Donna S. Shewach / Carl D. Morrison /
    Mikhail A. Nikiforov

    Cell Reports, Vol 5, Iss 2, Pp 493-

    2013  Volume 507

    Abstract: Melanoma is one of the most aggressive types of human cancers, and the mechanisms underlying melanoma invasive phenotype are not completely understood. Here, we report that expression of guanosine monophosphate reductase (GMPR), an enzyme involved in de ... ...

    Abstract Melanoma is one of the most aggressive types of human cancers, and the mechanisms underlying melanoma invasive phenotype are not completely understood. Here, we report that expression of guanosine monophosphate reductase (GMPR), an enzyme involved in de novo biosynthesis of purine nucleotides, was downregulated in the invasive stages of human melanoma. Loss- and gain-of-function experiments revealed that GMPR downregulates the amounts of several GTP-bound (active) Rho-GTPases and suppresses the ability of melanoma cells to form invadopodia, degrade extracellular matrix, invade in vitro, and grow as tumor xenografts in vivo. Mechanistically, we demonstrated that GMPR partially depletes intracellular GTP pools. Pharmacological inhibition of de novo GTP biosynthesis suppressed whereas addition of exogenous guanosine increased invasion of melanoma cells as well as cells from other cancer types. Our data identify GMPR as a melanoma invasion suppressor and establish a link between guanosine metabolism and Rho-GTPase-dependent melanoma cell invasion.
    Keywords Biology (General) ; QH301-705.5
    Language English
    Publishing date 2013-10-01T00:00:00Z
    Publisher Elsevier
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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