A Secreted Tyrosine Kinase Acts in the Extracellular Environment

Cell. Volume 158, Issue 5, 28 August 2014, Pages 1033–1044.

Although tyrosine phosphorylation of extracellular proteins has been reported to occur extensively in vivo, no secreted protein tyrosine kinase has been identified. As a result, investigation of the potential role of extracellular tyrosine phosphorylation in physiological and pathological tissue regulation has not been possible. Here, we show that VLK, a putative protein kinase previously shown to be essential in embryonic development, is a secreted protein kinase, with preference for tyrosine, that phosphorylates a broad range of secreted and ER-resident substrate proteins. We find that VLK is rapidly and quantitatively secreted from platelets in response to stimuli and can tyrosine phosphorylate coreleased proteins utilizing endogenous as well as exogenous ATP sources. We propose that discovery of VLK activity provides an explanation for the extensive and conserved pattern of extracellular tyrosine phosphophorylation seen in vivo, and extends the importance of regulated tyrosine phosphorylation into the extracellular environment.

Penn team finds ovarian cancer oncogene in 'junk DNA'

(http://www.eurekalert.org/pub_releases/2014-09/uops-ptf090514.php)

PHILADELPHIA - Over the years researchers have made tremendous strides in the understanding and treatment of cancer by searching genomes for links between genetic alterations and disease.

Most of those studies have focused on the portion of the human genome that encodes protein – a fraction that accounts for just 2 percent of human DNA overall. Yet the vast majority of genomic alterations associated with cancer lie outside protein-coding genes, in what traditionally has been derided as "junk DNA." Researchers today know that "junk DNA" is anything but – much of it is transcribed into RNA, for instance -- but finding meaning in those sequences remains a challenge.

Now a team led by Lin Zhang, PhD, research associate professor in the Department of Obstetrics and Gynecology at the Perelman School of Medicine at the University of Pennsylvania, has mined those sequences to identify a non-protein-coding RNA whose expression is linked to ovarian cancer. The study is published online in this week in Cancer Cell.

Supported by the Basser Research Center for BRCA in Penn's Abramson Cancer Center, Zhang and his team built a DNA copy number profile for nearly 14,000 long non-coding RNA, or lncRNAs, across 12 cancer types, including ovarian and breast cancers -- the two major BRCA-related cancers. They found that the number of copies of lncRNA genes on a chromosome consistently change in 12 different cancer types and lncRNA genes are widely expressed in cancer cells.

What these non-protein-coding RNAs do is still relatively unknown. However, given their vast numbers in the human genome, researchers believe that they likely play important roles in normal human development and response to disease.

Using clinical, genetic, and gene expression data as filters to distinguish genes whose copy number alteration causes cancer from those for whom copy number changes are incidental, the team whittled down their list from 14,000 to a more manageable number, each of which they systematically tested using genetic experiments in animals.

Of the 37 lncRNAs the team fully tested, one, which they called focally amplified lncRNA on chromosome 1, or FAL1, had all the makings of an RNA oncogene. FAL1 is one of only a handful of lncRNAs to be linked to cancer to date. This knowledge is being applied for clinical applications. For example, FAL1 expression may be a biomarker of BRCA-related cancer prognosis and the basis of new anti-cancer therapeutics. As proof-of-principle of the potential efficacy, Zhang's team grew human ovarian tumors in immunocompromised mice, then injected short-interfering RNAs to block the tumors' growth using RNA interference against FAL1. The tumors in treated animals shrank over the course of the experiment, while tumors in control animals continued to grow.

Enzyme controlling metastasis of breast cancer identified

(http://www.eurekalert.org/pub_releases/2014-09/uoc--ecm090214.php)

Researchers at the University of California, San Diego School of Medicine have identified an enzyme that controls the spread of breast cancer. The findings, reported in the current issue of PNAS, offer hope for the leading cause of breast cancer mortality worldwide. An estimated 40,000 women in America will die of breast cancer in 2014, according to the American Cancer Society.

"The take-home message of the study is that we have found a way to target breast cancer metastasis through a pathway regulated by an enzyme," said lead author Xuefeng Wu, PhD, a postdoctoral researcher at UC San Diego.

The enzyme, called UBC13, was found to be present in breast cancer cells at two to three times the levels of normal healthy cells. Although the enzyme's role in regulating normal cell growth and healthy immune system function is well-documented, the study is among the first to show a link to the spread of breast cancer.

Specifically, Wu and colleagues with the UC San Diego Moores Cancer Center found that the enzyme regulates cancer cells' ability to transmit signals that stimulate cell growth and survival by regulating the activity of a protein called p38 which when "knocked down" prevents metastasis. Of clinical note, the researchers said a compound that inhibits the activation of p38 is already being tested for treatment of rheumatoid arthritis.

In their experiments, scientists took human breast cancer cell lines and used a lentivirus to silence the expression of both the UBC13 and p38 proteins. These altered cancer cells were then injected into the mammary tissues of mice. Although the primary tumors grew in these mice, their cancers did not spread.

"Primary tumors are not normally lethal," Wu said. "The real danger is cancer cells that have successfully left the primary site, escaped through the blood vessels and invaded new organs. It may be only a few cells that escape, but they are aggressive. Our study shows we may be able to block these cells and save lives."

Researchers have also defined a metastasis gene signature that can be used to evaluate clinical responses to cancer therapies that target the metastasis pathway.

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Co-authors include: Weizhou Zhang, UC San Diego and University of Iowa; Joan Font-Burgada,Trenis Palmer, Alexander S. Hamil, Lesley G. Ellies, Jing Yang, Steven F. Dowdy and Michael Karin, UC San Diego; Subhra K. Biswas, Agency for Science, Technology and Research, Singapore; Michael Poidinger, Agency for Science, Technology and Research, Singapore and National University of Singapore; Nicholas Borcherding and Qing Xie, University of Iowa; Nikki K. Lytle, Raymond G. Fox and Tannishtha Reya, UC San Diego and Sanford Consortium for Regenerative Medicine; Li-Wha Wu, UC San Diego and National Cheng Kung University, Taiwan.

Funding for this study was provided, in part, by Susan G. Komen for the Cure, National Institutes of Health (grants CA163798 and AI043477) and Pedal the Cause San Diego.