Purpose: Multiple aspects of the tumor microenvironment (TME) impact breast cancer, yet the genetic modifiers of the TME are largely unknown, including those that modify tumor vascular formation and function. Methods: To discover host TME modifiers, we developed a system called the Consomic/Congenic Xenograft Model (CXM). In CXM, human breast cancer cells are orthotopically implanted into genetically engineered consomic xenograft host strains that are derived from two parental strains with different susceptibilities to breast cancer. Because the genetic backgrounds of the xenograft host strains differ, whereas the inoculated tumor cells are the same, any phenotypic variation is due to TME-specific modifier(s) on the substituted chromosome (consomic) or subchromosomal region (congenic). Here, we assessed TME modifiers of growth, angiogenesis, and vascular function of tumors implanted in the SSIL2Rγ and SS.BN3IL2Rγ CXM strains. Results: Breast cancer xenografts implanted in SS.BN3IL2Rγ (consomic) had significant tumor growth inhibition compared with SSIL2Rγ (parental control), despite a paradoxical increase in the density of blood vessels in the SS.BN3IL2Rγ tumors. We hypothesized that decreased growth of SS.BN3IL2Rγ tumors might be due to nonproductive angiogenesis. To test this possibility, SSIL2Rγ and SS.BN3IL2Rγ tumor vascular function was examined by dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI), micro-computed tomography (micro-CT), and ex vivo analysis of primary blood endothelial cells, all of which revealed altered vascular function in SS.BN3IL2Rγ tumors compared with SSIL2Rγ. Gene expression analysis also showed a dysregulated vascular signaling network in SS.BN3IL2Rγ tumors, among which DLL4 was differentially expressed and co-localized to a host TME modifier locus (Chr3: 95–131 Mb) that was identified by congenic mapping. Conclusions: Collectively, these data suggest that host genetic modifier(s) on RNO3 induce nonproductive angiogenesis that inhibits tumor growth through the DLL4 pathway.
Bibliographical noteFunding Information:
We thank M. Tschannen, R. Schilling, E. Schneider, A. Zappa, and Y. Liu for excellent technical support and the Center for Imaging Research in the Medical College of Wisconsin Department of Radiology, and the Biomedical Imaging Shared Resource supported by the MCW Cancer Center. This work was supported by a seed grant from the Wisconsin Breast Cancer Showhouse and the MCW Cancer Center, the Mary Kay Foundation (Grant No. 024.16), and the NCI (R01CA193343) to M.J.F. Support was also received from the National Center for Research Resources, the National Center for Advancing Translational Sciences, and the Office of the Director of the NIH via the Clinical & Translational Science Institute (#8KL2TR000056), the Wisconsin Breast Cancer Showhouse and the MCW Cancer Center, the Rosenberg Translational Research Award, and an institutional research Grant (#86-004-26) from the American Cancer Society to C.B. The authors have no conflict of interests to declare.
- Breast cancer
- RNA sequencing
- Tumor microenvironment