Abstract C05: Pulmonary laminin 332 in tumor cell migration and breast cancer survival

Metastasis to the lung often leads to the demise of the patient, thus a greater understanding of the process might lead to strategies for better cancer control. Tumor cell metastatic ability is determined by both intrinsic properties of tumor cells and contributions from the microenvironment. The goal of this study was to determine the role of the extracellular matrix protein laminin 332 (LN332) in breast cancer progression. Because tumor cell motility is a requirement for metastasis, we hypothesize that lung tissue harbors substances that induce tumor cell migration. In order to better characterize the interaction of breast carcinoma cells and lung tissue, MCF-7 breast carcinoma cells were added to slides of frozen sections of lung tissue. MCF-7 cells in contact with the lung tissue exhibited properties associated with tumor cell migration, including pseudopodia and lamellipodia. In contrast, MCF-7 cells on glass without lung tissue had smooth borders. Similarly, MCF-7 cells showed migratory properties when co-cultured with small airway epithelial cells (SAEC). LN332 is a component of the basement membrane of lung epithelium, and is thought to induce the migration of several tumor cell types. Immunoblotting revealed all three chains of LN332 in SAEC conditioned medium. To confirm that LN332 was among the components of the lung cells that induced the migration of the breast carcinoma cells, siRNA knockdown of the α3, β3 and γ2 chains of LN332 was performed on SAEC. The conditioned media from knock down and control SAEC was collected for motility assays. Knockdown of the α3 chain alone was sufficient to decrease the expression of the other two chains, but the greatest knockdown of LN332 protein was achieved with simultaneous use of siRNA against the α3, β3 and γ2 chains combined. Conditioned medium from cells with knockdown of LN332 induced tumor cell migration to a lesser extent than conditioned medium from control cells. Taken together, these in vitro data provide evidence that LN332 in the microenvironment has the potential to promote the invasion of metastatic foci into the pulmonary parenchyma. Next, we sought to determine whether LN332 expressed in breast carcinoma cells was associated with any particular phenotype of the tumors, or were associated with tumor prognosis. Tissue microarrays of breast carcinomas excised in 1994 and 1995 from 312 patients were stained for estrogen receptor, progesterone receptor, HER2 and the LN332 β3 chain by immunohistochemistry. LN332 expression was greatest in triple negative and HER2 expressing breast carcinomas. Follow-up for over 20 years on this cohort revealed that patients with tumors expressing LN332 β3 chain had a worse prognosis than patients without LN332 β3 chain in their tumors. Taken together, these studies provide evidence that LN332 in either tumor cells or the microenvironment may be implicated in breast cancer progression. Citation Format: Philip M. Carpenter, Priyanka Sivadas, Argyrios Ziogas, Hoda Anton-Culver. Pulmonary laminin 332 in tumor cell migration and breast cancer survival. [abstract]. In: Proceedings of the AACR Special Conference: Function of Tumor Microenvironment in Cancer Progression; 2016 Jan 7–10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2016;76(15 Suppl):Abstract nr C05.