DNA Damage Response to Ionizing Radiation Defective in the Invasive Cancer Phenotype

The purpose of this study was to determine the differences in DNA damage responses (DDRs) between immortalized normal prostate epithelial cells (PrEC) and prostate cancer cells (DU145). To study the DDRs, two protein markers were used. The first, phosphorylated KRAB Associated Protein 1 (pKAP-1) activates target genes involved in the DDR. The second, phosphorylated H2AX (pH2AX) is required for the assembly of damaged chromatin as well as for activation of checkpoints proteins. Ionizing Radiation (IR) was used to induce DNA damage. Flow Cytometry and Western Blot analyses were used to measure the levels of the proteins when exposed to various doses of IR (0, 2, 4, 8 Gy). In both cell lines, there was a clear dose dependent increase in pH2AX and pKAP-1, however error bars showed that with the pH2AX protein, only the later doses showed significant differences. Fluorescence staining was used to examine the localization of the proteins. Both cell lines showed punctate staining of pH2AX in the nuclei at 8Gy and no staining in unirradiated cells. With pKAP-1, the PrEC cells had punctate staining in the nuclei with 8Gy of radiation whereas the DU145 cells had a diffuse pattern in the nuclei

Novel Regulation of Integrin Trafficking by Rab11-FIP5 in Aggressive Prostate Cancer

The laminin-binding integrins, alpha 3 beta 1 and alpha 6 beta 1, are needed for tumor metastasis and their surface expression is regulated by endocytic recycling. beta 1 integrins share the Rab11 recycling machinery, but the trafficking of alpha 3 beta 1 and alpha 6 beta 1 are distinct by an unknown mechanism. Using a mouse PDX tumor model containing human metastatic prostate cancer, Rab11 family interacting protein 5 (Rab11-FIP5) was identified as a lead candidate for a6b1 trafficking. Rab11-FIP5 and its membrane-binding domain were required for alpha 6 beta 1 recycling, without affecting the other laminin-binding integrin (i.e., alpha 6 beta 1) or unrelated membrane receptors like CD44, transferrin receptor, or E-cad-herin. Depletion of Rab11-FIP5 resulted in the intracellular accumulation of alpha 6 beta 1 in the Rab11 recycling compartment, loss of cell migration on laminin, and an unexpected loss of alpha 6 beta 1 recycling in cell-cell locations. Taken together, these data demonstrate that alpha 6 beta 1 is distinct from alpha 3 beta 1 via Rab11-FIP5 recycling and recycles in an unexpected cell-cell location.Pacific Northwest Prostate Cancer SPORE [P50CA97186]; PO1 NIH grant [PO1CA085859]; Richard M. LUCAS Foundation; Tim and Diane Bowden Cancer Biology Fellowship Award; NIH [NIDDKR01-DK064380]; [NIH-NCIRO1CA159406]; [NIH-NCIRO1CA154835]; [P30CA23074]12 month embargo; published online: 14 May 2018This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Characterization of Laminin Binding Integrin Internalization in Prostate Cancer Cells

Laminin binding integrins 6 (CD49f) and 3 (CD49c) are persistently but differentially expressed in prostate cancer (PCa). Integrin internalization is an important determinant of their cell surface expression and function. Using flow cytometry, and first order kinetic modeling, we quantitated the intrinsic internalization rates of integrin subunits in a single cycle of internalization. In PCa cell line DU145, 6 integrin internalized with a rate constant (k(actual)) of 3.25min(-1), threefold faster than 3 integrin (1.0min(-1)), 1.5-fold faster than the vitronectin binding v integrin (CD51) (2.2min(-1)), and significantly slower than the unrelated transferrin receptor (CD71) (15min(-1)). Silencing of 3 integrin protein expression in DU145, PC3, and PC3B1 cells resulted in up to a 1.71-fold increase in k(actual) for 6 integrin. The internalized 6 integrin was targeted to early endosomes but not to lamp1 vesicles. Depletion of 3 integrin expression resulted in redistribution of 64 integrin to an observed cell-cell staining pattern that is consistent with a suprabasal distribution observed in epidermis and early PIN lesions in PCa. Depletion of 3 integrin increased cell migration by 1.8-fold, which was dependent on 61 integrin. Silencing of 6 integrin expression however, had no significant effect on the k(actual) of 3 integrin or its distribution in early endosomes. These results indicate that 3 and 6 integrins have significantly different internalization kinetics and that coordination exists between them for internalization. J. Cell. Biochem. 118: 1038-1049, 2017.NIH [R01 CA 159406, CA 23074, CA 09213]12 month embargo; Accepted manuscript online: 10 August 2016This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]