PINCH1 regulates Akt1 activation and enhances radioresistance by inhibiting PP1α
Iris Eke, Ulrike Koch, Stephanie Hehlgans, Veit Sandfort, Fabio Stanchi, Daniel Zips, Michael Baumann, Anna Shevchenko, Christian Pilarsky, Michael Haase, Gustavo B. Baretton, Véronique Calleja, Banafshé Larijani, Reinhard Fässler, Nils Cordes
Iris Eke, Ulrike Koch, Stephanie Hehlgans, Veit Sandfort, Fabio Stanchi, Daniel Zips, Michael Baumann, Anna Shevchenko, Christian Pilarsky, Michael Haase, Gustavo B. Baretton, Véronique Calleja, Banafshé Larijani, Reinhard Fässler, Nils Cordes
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Research Article Oncology

PINCH1 regulates Akt1 activation and enhances radioresistance by inhibiting PP1α

Abstract

Tumor cell resistance to ionizing radiation and chemotherapy is a major obstacle in cancer therapy. One factor contributing to this is integrin-mediated adhesion to ECM. The adapter protein particularly interesting new cysteine-histidine-rich 1 (PINCH1) is recruited to integrin adhesion sites and promotes cell survival, but the mechanisms underlying this effect are not well understood. Here we have shown that PINCH1 is expressed at elevated levels in human tumors of diverse origins relative to normal tissue. Furthermore, PINCH1 promoted cell survival upon treatment with ionizing radiation in vitro and in vivo by perpetuating Akt1 phosphorylation and activity. Mechanistically, PINCH1 was found to directly bind to protein phosphatase 1α (PP1α) — an Akt1-regulating protein — and inhibit PP1α activity, resulting in increased Akt1 phosphorylation and enhanced radioresistance. Thus, our data suggest that targeting signaling molecules such as PINCH1 that function downstream of focal adhesions (the complexes that mediate tumor cell adhesion to ECM) may overcome radio- and chemoresistance, providing new therapeutic approaches for cancer.

Authors

Iris Eke, Ulrike Koch, Stephanie Hehlgans, Veit Sandfort, Fabio Stanchi, Daniel Zips, Michael Baumann, Anna Shevchenko, Christian Pilarsky, Michael Haase, Gustavo B. Baretton, Véronique Calleja, Banafshé Larijani, Reinhard Fässler, Nils Cordes

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Figure 1

PINCH1 determines cellular sensitivity to ionizing radiation in vitro and in vivo.

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PINCH1 determines cellular sensitivity to ionizing radiation in vitro an...
(A) Western blot analysis of PINCH1, EGFP-PINCH1, and EGFP expression in MEFs. β-Actin served as loading control. (B) Mean ± SD results from 2D or 3D clonogenic survival assays of nonirradiated or irradiated (0–6 Gy X-rays) lrECM cell cultures (n = 3; *P < 0.05, **P < 0.01, t test). (C) Representative images of 2D and 3D lrECM colony formation of nonirradiated or irradiated PINCH1fl/fl and PINCH1–/– MEF cultures at 11 days after plating. Scale bars: 50 μm. (D) Experimental in vivo setup. Subcutaneous allograft PINCH1fl/fl and PINCH1–/– tumors were grown in immunocompromised mice. After tumor formation (diameter approximately 6 mm), tumors were locally irradiated with increasing single doses of 26–62 Gy under homogeneous hypoxia (200 kV X-rays, 0.5 mm copper filter, dose rate approximately 1.3 Gy/min). Tumor volume was measured over a time period of 210 days after irradiation. (E and F) Volume of PINCH1fl/fl and PINCH1–/– allograft tumors in immunocompromised mice plotted against time after irradiation (mean ± SEM; n = 10–18 per group), and tumor recurrence–free survival of PINCH1fl/fl and PINCH1–/– tumor-bearing mice (Kaplan-Meier statistics and log-rank test) after irradiation (see also Supplemental Figure 3).