Project Title: Investigation of RalA and RalB function in Triple Negative Breast Cancer Utilizing GEMMs
Project Mentor: Steven Sizemore – Radiation Oncology
Triple negative breast cancer (TNBC) is a subtype of breast cancer (BC) which displays high metastasis and poor prognosis. TNBC lacks three key receptors targeted for therapy – ER, PR, and HER2 – expressed by the other BC subtypes. Without these targets, treatments for TNBC are limited. RalA and RalB are potentially targetable small G-proteins which share 88% homology. Despite this similarity, RalA and RalB often show disparity of function. Recent studies in our laboratory revealed a pro-tumorigenic and pro-metastatic role for RalA in TNBC while RalB showed the opposite. To better understand the specific functions of the Rals in TNBC we have developed genetically engineered mouse models (GEMMs) to investigate Ral involvement in normal mammary development and during mammary tumorigenesis and metastasis. To generate the experimental cohorts, male mice carrying MMTV-cre, MMTV-PyMT, and homozygous-floxed Ral (Ralafl/fl or Ralbfl/fl) alleles were bred with female Ralfl/fl mice. These cohorts included: 1) MMTV-cre; Ralfl/fl and respective control female mice to study the roles of Rala and Ralb in normal mammary gland development and 2) MMTV-cre; MMTV-PyMT; Ralfl/fl and respective control female mice to investigate the roles of the Rals during spontaneous tumorigenesis and metastasis. In this model, expression of Cre recombinase (knocks out Ral allele) and PyMT oncogene are driven by the mouse mammary tumor virus (MMTV) promoter and thus effects are limited to the mammary gland. These mouse cohorts have recently been established. Mammary glands will be harvested at various time points, stained and scored for ductal length. For the tumor model, mice will be palpated regularly and the impact of Ral knockout on tumor initiation and growth will be studied. Lungs from these mice will be analyzed to determine the roles of Rala or Ralb on metastasis. Immunohistochemical staining will be used to analyze Rala or Ralb deletions and rate of tumor proliferation and apoptosis at time of harvest. The results of these studies will be the first examination of the impact of the Rals in normal mammary gland function and will be the first test of Ral necessity during mammary tumor initiation, growth, and metastasis in a GEMM.
Keywords: TNBC, RalA and RalB, GEMMs