Abstract C44: Metastatic potential of prostate tumor cells is affected by hyaluronan metabolism.
Authors: Kovar Joy L. , Olive D. Michael , Simpson Melanie A. 
Published: June 2012

Introduction: Accumulation of hyaluronan (HA) and elevation of the HA hydrolytic enzyme Hyal1 have been shown to promote prostate cancer progression. Immunohistochemical detection of HA and Hyal1 is diagnostic in biopsies and resected tissue, and predicts biochemical recurrence. We previously found that stable co-overexpression of Hyal1 and HAS, the HA biosynthetic enzyme, in 22Rv1 prostate tumor cells accelerates orthotopic tumor growth and spontaneous lymph node (LN) metastasis. Furthermore, the presence of cell-associated HA is required for adhesion of prostate tumor cells to bone marrow derived endothelial cells in vitro, suggesting surface HA could impact metastatic preference and/or efficiency of tumor cells by promoting arrest in specific vasculatures such as that of the bone. Here, we tested this hypothesis using intracardiac (IC) injections to model the hematogenous metastatic spread of tumor cells.

Experimental Procedures: Male nu/nu, nude/SCID and NOD/SCID mice were injected via the left ventricle with 1×105 tumor cells in 0.1 ml HBSS containing IRDye 800CW carboxylate, a non-reactive near infrared (NIR) imaging agent, as an indicator of successful injection. Mice (n=75) were monitored over a 10 week period by non-invasive fluorescent optical imaging of dual probes in the 700 and 800 channels of the Pearl Impulse Small Animal Imager. Probes were designed to identify tumor tissue (IRDye 800CW conjugated to EGF, 2DG, or RGD), lymphatic tissue (IRDye 680RD hyaluronan (HA)) or bone tissue (IRDye 680RD BoneTag). Animals were imaged at the study endpoint and metastases noted. Tissues were excised, imaged ex vivo, and metastasis confirmed by histology.

Results: PC3M-LN4 highly metastatic HA-encapsulated prostate tumor cells produced macrometastases at a higher rate (33%) after 10 wks than 22Rv1 HA-deficient cells (14%) in nu/nu and NOD/SCID mice. Suspect lesions were present in lung, bone, liver, adrenals, kidney, brain, and LN. Hyal1 overexpressing 22Rv1 cells were more frequently metastatic to brain and lungs and more rapidly growing, since that group exhibited a higher mortality rate. However, the frequency of metastasis observed in LN and bone was significantly higher for HAS transfectants, which also showed greater overall tumor burden in LN.

Conclusions: Although Hyal1 expression promotes LN growth via lymphatic invasion from prostate, HAS expression and surface HA retention provide a greater LN colonization advantage for tumor cells already in circulation. Use of IRDye 800CW and IRDye 680RD optical imaging agents in a multiplex fashion provided strong evidence of macro- and micro-metastases along with additional detail relevant to the microenvironment upon intraoperative evaluation. In several instances the dual optical agent evaluation alerted us to the presence of suspect lesions subsequently confirmed by H&E staining.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr C44.