Abstract B95: Examining reciprocal temporal interactions between human prostate cancer cells and the bone microenvironment
Authors: Howe Erin N. , Krishnan Venkatesh , Otto Kristen , Szmulewitz Russell Z. , Rinker-Schaeffer Carrie 
Published: August 2014

Introduction: Development of bone metastases continues to be the main source of morbidity and mortality in prostate cancer patients. Determining the mechanism(s) by which how prostate cancer cells utilize the bone microenvironment to survive and ultimately grow is key to developing strategies to prevent metastasis. Such approaches could affect disease morbidity and mortality, as nearly 80% patients have bone metastases at the time of death. The finding that disseminated cancer cells can be detected in 72% of patients prior to prostatectomy led to the realization that prostate cancer cells can disseminate early in the course of disease and persist in the bone for extended periods of time prior to detection (Melchior et al. 1997; William J Ellis et al. 2003; Morgan et al. 2009). However, not all patients with detectable tumor cells in the bone marrow will develop metastases (Morgan et al. 2009). It is now appreciated that this may be, in part due to factors within the metastatic microenvironment that restrict cancer cell growth. We speculate that one mechanism used by cancer cells to evade these growth suppressive effects is to modify the both the microenvironment and themselves such that they can survive and thrive.

Hypothesis: We hypothesize that in order to form bone metastases, CWR22Rv1 and C4-2B human prostate cancer cells induce transcriptional changes in host cells that alter the cellular composition of the bone microenvironment to favor growth. In response, cancer cells up-regulate a 65 gene pro-colonization signature recently identified by our laboratory (Bainer et al. 2012), which enables metastatic outgrowth.

Methods: A critical first step toward testing our hypothesis is to quantitate the size, number and location of metastases formed at specific time intervals after intracardiac injection. To this end, CWR22Rv1 and C4-2B cells were engineered to express the synthetic firefly luciferase luc 2, and injected into the left ventricle of intact male, 8 week old NOD/SCID mice. Immediately post-injection, delivery of the cells into the circulation was assessed using the Xenogen IVIS 200. Tumor growth was assessed weekly from two to six weeks post injection.

Results: After injection, CWR22Rv1 cells lodge in the skeleton where they persist for approximately two weeks. The cells then undergo progressive growth (as indicated by increasing signal intensity), culminating in overt metastases at the experimental endpoint (6 weeks post injection). The 145-fold increase in luciferase signal was accompanied by osteoblastic-lesions in the skeleton, most notably calvarial lesions. Several animals developed additional metastases in the hind limbs.

Conclusions: This baseline data serves as a starting point for additional studies to more precisely define the kinetics of metastatic growth in this model system. Future work will identify molecular changes that occur in the prostate cancer cells and the bone microenvironment both during and prior to metastatic outgrowth.

Funding: DOD Award W81XWH-09-1-0415; DOD W81XWH-09-1-0449, NCI/NIH 2RO1CA089569; Section of Urology Research Funds.

Citation Format: Erin N. Howe, Venkatesh Krishnan, Kristen Otto, Russell Z. Szmulewitz, Carrie Rinker-Schaeffer. Examining reciprocal temporal interactions between human prostate cancer cells and the bone microenvironment. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Invasion and Metastasis; Jan 20-23, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;73(3 Suppl):Abstract nr B95.