IDENTIFYING GERMLINE GENES AS TARGETS FOR THERAPEUTIC INTERVENTION IN CANCER

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DESCRIPTION (provided by applicant): Recent progress in cancer research has highlighted a new category of targets for anti-cancer drugs: gene products expressed in the germline (Janic et al., 2010; Georlette et al., 2007; Wu and Ruvkun, 2010; Liu et al., 2011; Strumane et al., 2006; Caballero et al., 2009). Seminal work in Drosophila has shown that loss of a tumor suppressor gene causes brain malignancies that display a soma-to-germline transformation with 25% of up-regulated genes having a germline-associated function (Janic et al., 2010). Many of these tumor up-regulated genes are of maternal origin. Importantly, blocking the expression of these genes suppressed tumor growth. Germ cells share at least three important characteristics of cancer, the ability to: sustain a proliferative state, resist cell death, and undergo an epithelial-mesenchymal transition characteristic of invasion and metastasis. These findings strongly support the value of screening germ cell components for their ability to promote these behaviors as a step towards identifying potent therapeutic targets for cancer treatments. However, previous work on identifying germline components has relied almost entirely on RNA microarray data while the proteins remain largely unknown and the majority of RNAs uncharacterized, slowing progress in this area (Yatsu et al., 2008; Molyneaux et al., 2004; Ewen and Koopman, 2010). Germ plasm is the subcellular domain unique to germ cell precursors that contains all the determinants required to specify the germ cell lineage in diverse organisms. Our central hypothesis is that germ plasm will provide a rich source of new targets for anti-cancer drugs. Unfortunately, it is technically difficult to isolate germ plasm in sufficient quantities for proten analysis and thus, genetic information in vertebrates has been limited. Xenopus offers a unique opportunity to isolate biochemical quantities of germ plasm, making it possible, with current technology, to create a complete "parts list" of this cellular "machine" that specifies the totipotnt germ cell lineage. Moreover, Xenopus is highly amenable to expression cloning, allowing a high-throughput approach to assess gene function of germ plasm components. To test our central hypothesis, we will complete the following two specific aims: Aim 1. Identify the protein and RNA components of germ plasm and use this information to predict gene networks operating in the germline and up-regulated in cancer cell lines. Aim 2. Test these germ cell components for their ability to promote the biological "hallmarks" of cancer: metastasis, immortality, and proliferation in bioassays. In preliminary studies, we have isolated biochemical amounts of germ plasm and have identified over 400 proteins by Liquid Chromatography-tandem Mass Spectrometry analyses. We are now ready to launch into broader studies functionally screening germ plasm components for their possible relevance to cancer biology.