Abstract 2329: Alterations in laminin expression modulate prostate cancer cell behavior through changes in integrin and insulin-like growth factor receptor actions

Introduction: During development of primary prostate carcinomas alterations to the extracellular matrix occur, including a loss of laminin 332 (LM332) and one of its cell surface receptors, β₄ integrin. There are few published studies on what the laminin composition of metastases may be or how alterations in laminin expression affect prostate cancer cell behavior. Expression of the insulin-like growth factor receptor (IGF-IR) also is altered in prostate cancer progression and some studies suggest cross-talk between integrins and IGF-IR.

Purpose: To determine if laminin and integrin expression is altered in prostate cancer metastases and how these alterations affect prostate cancer cell behavior in light of the interactions between integrins and IGF-IR.

Methods: We performed immunofluorescent (IF) staining on tissue samples of primary PCa and metastases. We also used various prostate cancer cell lines, including M12 cells transfected with the LMα4, β2, or α4β2 chains, to perform adhesion, migration, and proliferation assays in the presence of inhibitory integrin and IGF-IR antibodies.

Results: Our IF staining demonstrated that in addition to a loss in LM332 expression, the LMα4 and β2 chains were absent from the prostate basal membrane in primary prostate tumors. Expression of the LMα5 and β1γ1 chains was retained in primary tumors as well as in lymph node metastases. We saw a loss of β₄ integrin in primary tumors as well as in metastatic cancer, but α₆ and β₁ integrins were retained; in lymph node mets, α₂ and α₃ integrins also were expressed.

For M12 laminin cells, enhanced adhesion to both collagen and fibronectin was further increased by treatment with the inhibitory IGF-IR antibody A12. An inhibitory β₁ integrin antibody, but not individual alpha integrin antibodies, blocked this enhancement. Inhibitory β₁ as well as alpha integrin antibodies blocked adhesion of the empty-vector control cells. Similar results were obtained for cell migration studies using a scratch-assay. Staining of cells following exposure to A12 showed there was an increase in LM332 and LMβ1γ1 expression compared to untreated cells, which may account for the increased adhesion and migration following A12 treatment.

We then examined laminin expression of various prostate cancer cell lines: LNCaP, LNCaP C4-2, PC3, and DU145. We found no expression of LM332 in any of these lines. Cytoplasmic expression of the LMβ1γ1 and LMβ2 (LNCaP lines) chains was detected, but deposition of these laminins was not present. These lines demonstrated increased adhesion to laminin-rich ECM compared with adhesion to fibronectin or collagen. And these lines showed enhanced proliferation when grown on laminin-rich ECM from the M12 laminin cells.

Summary: Alterations in laminins affect the adhesion, migration, and proliferation of prostate cancer cells, in part, through integrin and IGF-IR actions.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2329.