67-kDa laminin receptor increases cGMP to induce cancer-selective apoptosis
Motofumi Kumazoe, … , Koji Yamada, Hirofumi Tachibana
Motofumi Kumazoe, … , Koji Yamada, Hirofumi Tachibana
Published January 25, 2013
Citation Information: J Clin Invest. 2013;123(2):787-799. https://doi.org/10.1172/JCI64768.
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Research Article

67-kDa laminin receptor increases cGMP to induce cancer-selective apoptosis

Abstract

The 67-kDa laminin receptor (67LR) is a laminin-binding protein overexpressed in various types of cancer, including bile duct carcinoma, colorectal carcinoma, cervical cancer, and breast carcinoma. 67LR plays a vital role in growth and metastasis of tumor cells and resistance to chemotherapy. Here, we show that 67LR functions as a cancer-specific death receptor. In this cell death receptor pathway, cGMP initiated cancer-specific cell death by activating the PKCδ/acid sphingomyelinase (PKCδ/ASM) pathway. Furthermore, upregulation of cGMP was a rate-determining process of 67LR-dependent cell death induced by the green tea polyphenol (–)-epigallocatechin-3-O-gallate (EGCG), a natural ligand of 67LR. We found that phosphodiesterase 5 (PDE5), a negative regulator of cGMP, was abnormally expressed in multiple cancers and attenuated 67LR-mediated cell death. Vardenafil, a PDE5 inhibitor that is used to treat erectile dysfunction, significantly potentiated the EGCG-activated 67LR-dependent apoptosis without affecting normal cells and prolonged the survival time in a mouse xenograft model. These results suggest that PDE5 inhibitors could be used to elevate cGMP levels to induce 67LR-mediated, cancer-specific cell death.

Authors

Motofumi Kumazoe, Kaori Sugihara, Shuntaro Tsukamoto, Yuhui Huang, Yukari Tsurudome, Takashi Suzuki, Yumi Suemasu, Naoki Ueda, Shuya Yamashita, Yoonhee Kim, Koji Yamada, Hirofumi Tachibana

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Figure 1

67LR-dependent NO production by activation of Akt and eNOS is a key event in the EGCG-induced cell death pathway.

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67LR-dependent NO production by activation of Akt and eNOS is a key even...
(A) Primary MM cells, MM cell lines (U266 and RPMI8226), and normal PBMCs were cultured for 3 hours in the absence or presence of 5 μM EGCG. NO production was measured using the fluorescent probe DAF-2DA. FU, fluorescence units. (B) Cells were pretreated with control antibody or anti-67LR antibody (20 μg/ml) and treated or not with EGCG for 3 hours. Phosphorylation of eNOS at Ser1177 was measured by Western blotting. Lanes were run on the same gel but were noncontiguous (white lines). (C) U266 cells were pretreated or not with the NOS inhibitor l-NAME (10 mM), then cultured in medium with or without 10 μM EGCG for 96 hours. (D) Left: Immunoblot analyses of eNOS knockdown in U266 cells. Right: Sensitivity of U266 cells to EGCG (10 μM for 96 hours) after eNOS knockdown. (E) Effect of 5 μM EGCG on Akt activity. (F) Cells were pretreated with control antibody or anti-67LR antibody (20 μg/ml) and treated or not with 5 μM EGCG for 1 hour. (G) U266 cells were pretreated or not with 5 μM AKT1/2 kinase inhibitor, then cultured in medium with or without 5 μM EGCG for 3 hours. All data are mean ± SEM.