67-kDa laminin receptor increases cGMP to induce cancer-selective apoptosis
Motofumi Kumazoe, Kaori Sugihara, Shuntaro Tsukamoto, Yuhui Huang, Yukari Tsurudome, Takashi Suzuki, Yumi Suemasu, Naoki Ueda, Shuya Yamashita, Yoonhee Kim, Koji Yamada, Hirofumi Tachibana
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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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 3

Abnormal overexpression of PDE5 attenuates EGCG-induced cell death in MM cells.

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Abnormal overexpression of PDE5 attenuates EGCG-induced cell death in MM...
(A) MM cells were pretreated with the PDE1 inhibitor 8-Met-IBMX (20 μM), with the PDE4 inhibitor rolipram (10 μM), with the PDE5 inhibitors zaprinast (10 μM), sildenafil (10 μM), vardenafil (5 μM), and MQZ (10 μM), or with theophylline (20 μM), then treated or not with 5 μM EGCG for 96 hours. ***P < 0.001. (B) Cells were treated with or without 5 μM vardenafil and/or 5 μM EGCG for 96 hours. Phase-contrast images were taken by optical microscopy. Original magnification, ×20. (C) Expression of 67LR and PDE5 proteins in patient cells and normal PBMCs, assessed by immunoblotting. Lanes were run on the same gel but were noncontiguous (white lines). (D) Correlation between 67LR expression and PDE5 expression. (E) Top: Immunoblot analyses of PDE5 in U266 cells. Bottom: EGCG sensitivity (5 μM for 96 hours) of U266 cells after PDE5 knockdown. (F) Normal PBMCs from 10 healthy donors, primary MM cells from 10 patients, and MM cell lines were treated with or without 5 μM vardenafil and/or 5 μM EGCG for 96 hours. (G) U266 cells were incubated for 96 hours with or without 5 μM vardenafil and/or 5 μM EGCG analogs (see Figure 2F). n = 3 per group. All data are mean ± SEM.