Cancer-associated fibroblasts regulate endothelial adhesion protein LPP to promote ovarian cancer chemoresistance
Cecilia S. Leung, … , Michael J. Birrer, Samuel C. Mok
Cecilia S. Leung, … , Michael J. Birrer, Samuel C. Mok
Published December 18, 2017
Citation Information: J Clin Invest. 2018;128(2):589-606. https://doi.org/10.1172/JCI95200.
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Research Article Cell biology Oncology

Cancer-associated fibroblasts regulate endothelial adhesion protein LPP to promote ovarian cancer chemoresistance

Abstract

The molecular mechanism by which cancer-associated fibroblasts (CAFs) confer chemoresistance in ovarian cancer is poorly understood. The purpose of the present study was to evaluate the roles of CAFs in modulating tumor vasculature, chemoresistance, and disease progression. Here, we found that CAFs upregulated the lipoma-preferred partner (LPP) gene in microvascular endothelial cells (MECs) and that LPP expression levels in intratumoral MECs correlated with survival and chemoresistance in patients with ovarian cancer. Mechanistically, LPP increased focal adhesion and stress fiber formation to promote endothelial cell motility and permeability. siRNA-mediated LPP silencing in ovarian tumor–bearing mice improved paclitaxel delivery to cancer cells by decreasing intratumoral microvessel leakiness. Further studies showed that CAFs regulate endothelial LPP via a calcium-dependent signaling pathway involving microfibrillar-associated protein 5 (MFAP5), focal adhesion kinase (FAK), ERK, and LPP. Thus, our findings suggest that targeting endothelial LPP enhances the efficacy of chemotherapy in ovarian cancer. Our data highlight the importance of CAF–endothelial cell crosstalk signaling in cancer chemoresistance and demonstrate the improved efficacy of using LPP-targeting siRNA in combination with cytotoxic drugs.

Authors

Cecilia S. Leung, Tsz-Lun Yeung, Kay-Pong Yip, Kwong-Kwok Wong, Samuel Y. Ho, Lingegowda S. Mangala, Anil K. Sood, Gabriel Lopez-Berestein, Jianting Sheng, Stephen T.C. Wong, Michael J. Birrer, Samuel C. Mok

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Figure 2

LPP silencing increases paclitaxel uptake and suppresses tumor growth in vivo.

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LPP silencing increases paclitaxel uptake and suppresses tumor growth in...
(A) Hematoxylin- counterstained micrographs showing that endothelial Lpp expression in tumor tissues collected from mice treated with Lpp-targeting siRNAs was markedly lower than that in tumor tissues collected from control mice treated with scrambled siRNA (arrowheads indicate tumor microvessels). Scale bars: 50 μm. (B) Mice treated with Lpp-targeting siRNA 1or siRNA 2 had significantly smaller tumor burdens than did scrambled siRNA–treated mice (P = 0.0048 and P = 0.0008, respectively). In addition, paclitaxel-treated mice injected with Lpp-targeting siRNA 1 or Lpp-targeting siRNA 2 had significantly lower tumor weights than did scrambled siRNA–injected mice (n = 10/group; mean ± SD; P = 0.0055 and P = 0.0005, respectively, by Mann-Whitney U test). (C) Mice treated with Lpp-targeting siRNA 1 or siRNA 2 had significantly lower microvessel densities than did control group mice (n = 10/group; mean ± SD; P = 0.019 and P = 0.003, respectively, by Mann-Whitney U test). Microvessel densities were determined by immunolocalization of CD31-positive microvessels in harvested tumor nodules. (D) Fluorescence micrographs showing that the FITC-dextran signals in ovarian tumor tissues harvested from mice treated with Lpp-targeting siRNA 1 and from mice treated with Lpp-targeting siRNA 2 were significantly lower than those in ovarian tumor tissues from control mice, indicating reduced vessel leakiness in tumors from mice treated with Lpp-targeting siRNAs. Mice were injected with FITC-dextran via the tail vein 1 hour before sacrifice. Tumor vessel leakiness was evaluated by fluorescence microscopic quantification of tumor tissue FITC-dextran signals. Green: FITC-dextran; red: CD31. (E) Fluorescence-labeled paclitaxel signals in ovarian tumor tissues harvested from mice treated with Lpp-targeting siRNA 1 and from mice treated with Lpp-targeting siRNA 2 were significantly higher than those in control tumor tissues, suggesting increased drug delivery to the tumors via circulation in mice treated with Lpp-targeting siRNAs. Mice were injected with Oregon Green 488 fluorescence–labeled paclitaxel via the tail vein 1 hour before sacrifice. Drug delivery was evaluated by quantifying the green fluorescence signals in the tumor tissue. Green: Oregon Green 488–paclitaxel; red: CD3. (D and E) Scale bars: 100 μm (top), 50 μm (bottom).