Hpr6 Mutants and Uses Thereof

Methods and agents that interfere with Hpr6 function in non-sarcoma tumor cells are disclosed. Anti-Hpr6 agents are used to enhance the killing effect of anti-cancer agents in non-sarcoma tumor cells and to teat non-sarcoma tumors

Secreted Tumor-Associated Cytochrome as a Blood-Based Biomarker for Cancer

Disclosed herein are methods for detecting Pgrmc 1 in bodily fluids, e.g., blood, plasma and serum, wherein detection of Pgrmcl is a biomarker for the presence of cancer, e.g., lung cancer or head or neck cancer. Pgrmc 1 levels in bodily fluids may be used to predict patient prognosis, e.g., survival and response to therapy

AG-205 for the Treatment of Breast Cancer

Compositions, methods, and combination therapies for the treatment of cancers, including lymphomas, leukemias, melanomas, lung cancer, and metastatic disease, are provided. Specifically, compositions comprising ligands to Pgrmc1 are disclosed for use in treating and inhibiting tumor growth and progression and inhibition of metastases. The compositions and methods using these ligands can be used alone or in combination with other reagents and cancer treatment modalities

The Rak/Frk Tyrosine Kinase Associates With and Internalizes the Epidermal Growth Factor Receptor

Src is the founding member of a diverse family of intracellular tyrosine kinases, and Src has a key role in promoting cancer growth, in part, through its association with receptor tyrosine kinases. However, some Src-related proteins have widely divergent physiological roles, and these proteins include the Rak/Frk tyrosine kinase (Frk stands for Fyn-related kinase), which inhibits cancer cell growth and suppresses tumorigenesis. Rak/Frk phosphorylates and stabilizes the Pten tumor suppressor, protecting it from degradation, and Rak/Frk associates with the retinoblastoma (Rb) tumor suppressor. However, the role of Rak/Frk in receptor-mediated signaling is largely unknown. Here, we demonstrate that Rak/Frk associates with epidermal growth factor receptor (EGFR), increasing in activity and EGFR binding after EGF stimulation, when it decreases the pool of EGFR present at the plasma membrane. EGFR-Rak binding is direct, requires the SH2 and SH3 domains of Rak/Frk for efficient complex formation and is not dependent on the Grb2 adaptor protein. EGFR mutations are associated with increased EGFR activity and tumorigenicity, and we found that Rak/Frk associates preferentially with an EGFR exon 19 mutant, EGFRΔ747-749/A750P, compared with wild-type EGFR. Furthermore, Rak/Frk inhibited mutant EGFR phosphorylation at an activating site and dramatically decreased the levels of EGFRΔ747-749/A750P from the plasma membrane. Taken together, the results suggest that Rak/Frk inhibits EGFR signaling in cancer cells and has elevated activity against EGFR exon 19 mutants

Dependence of the regulation of telomere length on the type of subtelomeric repeat in the yeast Saccharomyces cerevisiae.

In the yeast Saccharomyces cerevisiae, chromosomes terminate with approximately 400 bp of a simple repeat poly(TG(1-3)). Based on the arrangement of subtelomeric X and Y' repeats, two types of yeast telomeres exist, those with both X and Y' (Y' telomeres) and those with only X (X telomeres). Mutations that result in abnormally short or abnormally long poly(TG(1-3)) tracts have been previously identified. In this study, we investigated telomere length in strains with two classes of mutations, one that resulted in short poly(TG(1-3)) tracts (tel1) and one that resulted in elongated tracts (pif1, rap1-17, rif1, or rif2). In the tel1 pif1 strain, Y' telomeres had about the same length as those in tel1 strains and X telomeres had lengths intermediate between those in tel1 and pif1 strains. Strains with either the tel1 rap1-17 or tel1 rif2 genotypes had short tracts for all chromosome ends examined, demonstrating that the telomere elongation characteristic of rap1-17 and rif2 strains is Tel1p-dependent. In strains of the tel1 rif1 or tel1 rif1 rif2 genotypes, telomeres with Y' repeats had short terminal tracts, whereas most of the X telomeres had long terminal tracts. These results demonstrate that the regulation of telomere length is different for X and Y' telomeres

Regulation of Iron Homeostasis Mediated by the Heme-binding Protein Dap1 (Damage Resistance Protein 1) via the P450 Protein Erg11/Cyp51

Fungal infections arise frequently in immunocompromised patients, and sterol synthesis is a primary pathway targeted by antifungal drugs. In particular, the P450 protein Erg11/Cyp51 catalyzes a critical step in ergosterol synthesis, and the azole class of antifungal drugs inhibits Erg11. Dap1 is a heme-binding protein related to cytochrome b5 that activates Erg11, so that cells lacking Dap1 accumulate the Erg11 substrate and are hypersensitive to Erg11 inhibitors. Heme binding by Dap1 is crucial for its function, and point mutants in its heme-binding domain render Dap1 inactive for sterol biosynthesis and DNA damage resistance. Like Dap1, the human homologue, PGRMC1/Hpr6, also regulates sterol synthesis and DNA damage resistance. In the present study, we demonstrate that the Dap1 heme-1 domain is required for growth under conditions of low iron availability. Loss of Dap1 is suppressed by elevated levels of Erg11 but not by increased heme biosynthesis. Dap1 localizes to punctate cytoplasmic structures that co-fractionate with endosomes, and Dap1 contributes to the integrity of the vacuole. The results suggest that Saccharomyces cerevisiae Dap1 stimulates a P450-catalyzed step in sterol synthesis via a distinct localization from its homologues in Schizosaccharomyces pombe and mammals and that this function regulates iron metabolism

Regulation of genome stability by TEL1 and MEC1, yeast homologs of the mammalian ATM and ATR genes.

In eukaryotes, a family of related protein kinases (the ATM family) is involved in regulating cellular responses to DNA damage and telomere length. In the yeast Saccharomyces cerevisiae, two members of this family, TEL1 and MEC1, have functionally redundant roles in both DNA damage repair and telomere length regulation. Strains with mutations in both genes are very sensitive to DNA damaging agents, have very short telomeres, and undergo cellular senescence. We find that strains with the double mutant genotype also have approximately 80-fold increased rates of mitotic recombination and chromosome loss. In addition, the tel1 mec1 strains have high rates of telomeric fusions, resulting in translocations, dicentrics, and circular chromosomes. Similar chromosome rearrangements have been detected in mammalian cells with mutations in ATM (related to TEL1) and ATR (related to MEC1) and in mammalian cells that approach cell crisis

PGRMC1: a new biomarker for the estrogen receptor in breast cancer

Estrogen receptor (ER) status is a critical biomarker in breast cancer, in large part because the ER is the target of tamoxifen and similar drugs. In the previous issue of Breast Cancer Research, Neubauer and colleagues used a proteomic approach to identify proteins that are differentially regulated by ER in breast tumors. The authors showed that ER-negative tumors have elevated levels of PGRMC1 (progesterone receptor membrane component-1), a hormone receptor component and binding partner for P450 proteins. In contrast, PGRMC1 was phosphorylated in ER-positive tumors. The staining patterns of ER and PGRMC1 were mutually exclusive in breast tumor sections, and PGRMC1 staining was sharply increased in hypoxic areas of the tumor. The results suggest that PGRMC1 is a candidate biomarker for ER status and hypoxia in breast cancer

Dual Inhibition of Focal Adhesion Kinase and Epidermal Growth Factor Receptor Pathways Cooperatively Induces Death Receptor-mediated Apoptosis in Human Breast Cancer Cells

The focal adhesion kinase (FAK) and epidermal growth factor receptor (EGFR) are protein-tyrosine kinases that are overexpressed and activated in human breast cancer. To determine the role of EGFR and FAK survival signaling in breast cancer, EGFR was stably overexpressed in BT474 breast cancer cells, and each signaling pathway was specifically targeted for inhibition. FAK and EGFR constitutively co-immunoprecipitated in EGFR-overexpressing BT474 cells. In low EGFR-expressing BT474-pcDNA3 vector control cells, inhibition of FAK by the FAK C-terminal domain caused detachment and apoptosis via pathways involving activation of caspase-3 and -8, cleavage of poly(ADP-ribose) polymerase, and caspase-3-dependent degradation of AKT. This apoptosis could be rescued by the dominant-negative Fas-associated death domain, indicating involvement of the death receptor pathway. EGFR overexpression did not inhibit detachment induced by the FAK C-terminal domain, but did suppress apoptosis, activating AKT and ERK1/2 survival pathways and inhibiting cleavage of FAK, caspase-3 and -8, and poly(ADP-ribose) polymerase. Furthermore, this protective effect of EGFR signaling was reversed by EGFR kinase inhibition with AG1478. In addition, inhibition of FAK and EGFR in another breast cancer cell line (BT20) endogenously overexpressing these kinases also induced apoptosis via the same mechanism as in the EGFR-overexpressing BT474 cells. The results of this study indicate that dual inhibition of FAK and EGFR signaling pathways can cooperatively enhance apoptosis in breast cancers