01.19 Macrophage Expression of Pro-Metastatic Genes Altered After Surgical Resection In Osteosarcoma Model

M. P. Kallis1,2,3, B. Blank2,4, M. Symons2,5, B. M. Steinberg2,5, S. Z. Soffer1,3  1Donald and Barbara Zucker School Of Medicine at Hofstra/Northwell,Surgery And Pediatrics,Manhasset, NEW YORK, USA 2The Feinstein Institutes for Medical Research at Northwell Health,The Elemezzi Graduate School Of Molecular Medicine,Manhasset, NEW YORK, USA 3Cohen Children’s Medical Center at Northwell Health,Surgery,New Hyde Park, NY, USA 4Donald and Barbara Zucker School of Medicine at Hofstra/Northwell,Hempstead, NEW YORK, USA 5Donald and Barbara Zucker School of Medicine at Hofstra/ Northwell,Molecular Medicine,Manhasset, NEW YORK, USA

Introduction:  Primary tumor excision is the mainstay of treatment for osteosarcoma (OS).  However, surgical stress may promote metastatic growth, an effect known as surgery-accelerated metastasis. We have previously shown that surgical stress alters the proportion of macrophage populations within the lung to favor a pro-tumor macrophage phenotype. The transcriptional changes contributing to this phenotype are unknown. 

Methods:  Mouse OS cells (K7M2) were implanted into the tibia of BALB/c mice. Animals were then randomized into tumor-bearing or tumor-amputation groups (n=3-4 mice/group). The amputation group underwent amputation of the primary tumor-bearing limb at 1 week post tumor implantation. Both groups were sacrificed 4 weeks after tumor inoculation. Macrophages, defined as CD45+/F4/80+ double positive cells, were isolated from whole lung homogenate using fluorescence activated cell sorting (FACS). Mature macrophage RNA was isolated and reverse transcribed using a cDNA conversion kit and a PCR array examining genes related to cancer and immunity crosstalk was performed. Macrophage gene expression of experimental groups was compared to that of age-matched healthy controls.

Results: Implantation of a primary tumor alone resulted in a 5.8 fold increase in chemokine receptor type 4 (CXCR4) (p< 0.05). After surgical resection expression of CXCR4 increased 10.8 fold (p< 0.01). Chemokine receptor type 3 expression (CXCR3) decreased by 63 fold following implantation of a primary tumor (p > 0.01), and after surgical excision expression remained decreased by 11 fold compared to controls (P< 0.05). Signal transducer and activator of transcription 3 (STAT3) increased in expression 4 fold after implantation of tumor alone, and further increased after surgery to 5.25 fold (p< 0.05).

Conclusion: Implantation of a primary tumor increases expression of genes known to assist in migration, invasion, and adhesion in metastasis (CXCR4), as well as genes associated with immunosuppression and decreased tumor surveillance (STAT3). Tumor presence also results in decreased expression of a gene known to activate macrophage tumoricidal activity (CXCR3). Following surgical resection, the expression of these genes remain altered toward a pro-tumor and immunosuppressive phenotype compared to non-operated tumor-bearing mice, demonstrating the persistent tumorigenic environment in the enhanced metastatic niche post-operatively.