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Abstract PI3K–Akt signaling is critical for the development, progression, and metastasis of malignant tumors, but its role in the tumor microenvironment.

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Presentation on theme: "Abstract PI3K–Akt signaling is critical for the development, progression, and metastasis of malignant tumors, but its role in the tumor microenvironment."— Presentation transcript:

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6 Abstract PI3K–Akt signaling is critical for the development, progression, and metastasis of malignant tumors, but its role in the tumor microenvironment has been relatively little studied. Here, we report that the Akt substrate Girdin, an actin-binding protein that regulates cell migration, is expressed and activated by Akt phosphorylation in cancer-associated fibroblasts (CAF) and blood vessels within the tumor microenvironment. Lewis lung tumors grafted into mice defective in Akt-mediated Girdin phosphorylation (SA transgenic mice) exhibited a decrease in both CAF infiltration and tumor growth, compared with wild-type (WT) host control animals. Contrasting with the findings of other studies, we found that Akt-dependent phosphorylation of Girdin was not a rate-limiting step in the growth of endothelial cells. In addition, Lewis lung tumors displayed limited outgrowth when cotransplanted with CAF derived from tumor-bearing SA transgenic mice, compared with CAF derived from tumor-bearing WT mice. Collectively, our results revealed a role for Akt-mediated Girdin phosphorylation in CAF during tumor progression, highlighting the need to inhibit Akt function in both tumor cells and cells that comprise the tumor microenvironment. Cancer Res; 75(5); 813–23. ©2015 AACR.

7 Abstract Proliferating mammalian stem and cancer cells express telomerase [telomerase reverse transcriptase (TERT)] in an effort to extend chromosomal G-overhangs and maintain telomere ends. Telomerase-expressing cells also have higher levels of the single-stranded DNA-binding protein SSB1, which has a critical role in DNA double-strand break (DSB) repair. Here, we report that SSB1 binds specifically to G-strand telomeric DNA in vitro and associates with telomeres in vivo. SSB1 interacts with the TERT catalytic subunit and regulates its interaction with telomeres. Deletion of SSB1 reduces TERT interaction with telomeres and leads to G-overhang loss. Although SSB1 is recruited to DSB sites, we found no corresponding change in TERT levels at these sites, implying that SSB1–TERT interaction relies upon a specific chromatin structure or context. Our findings offer an explanation for how telomerase is recruited to telomeres to facilitate G-strand DNA extension, a critical step in maintaining telomere ends and cell viability in all cancer cells. Cancer Res; 75(5); 858–69. ©2015 AACR.

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12 [Science] 6 MARCH 2015 VOL 347, ISSUE 6226, PAGES 1041-116

13 [Science] 6 MARCH 2015 VOL 347, ISSUE 6226, PAGES 1041-116

14 [Science] 6 MARCH 2015 VOL 347, ISSUE 6226, PAGES 1041-116

15 [Science] 6 MARCH 2015 VOL 347, ISSUE 6226, PAGES 1041-116

16 [Science] 6 MARCH 2015 VOL 347, ISSUE 6226, PAGES 1041-116

17 [Science] 6 MARCH 2015 VOL 347, ISSUE 6226, PAGES 1041-116


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