Resf1 is a compound G4 quadruplex-associated tumor suppressor for triple negative breast cancer

Patients with ER-negative breast cancer have the worst prognosis of all breast cancer subtypes, often experiencing rapid recurrence or progression to metastatic disease shortly after diagnosis. Given that metastasis is the primary cause of mortality in most solid tumors, understanding metastatic biology is crucial for effective intervention. Using a mouse systems genetics approach, we previously identified 12 genes associated with metastatic susceptibility. Here, we extend those studies to identify Resf1, a poorly characterized gene, as a novel metastasis susceptibility gene in ER- breast cancer. Resf1 is a large, unstructured protein with an evolutionarily conserved intron-exon structure, but with poor amino acid conservation. CRISPR or gene trap mouse models crossed to the Polyoma Middle-T antigen genetically engineered mouse model (MMTV-PyMT) demonstrated that reduction of Resf1 resulted in a significant increase in tumor growth, a shortened overall survival time, and increased incidence and number of lung metastases, consistent with patient data. Furthermore, an analysis of matched tail and primary tissues revealed loss of the wildtype copy in tumor tissue, consistent with Resf1 being a tumor suppressor. Mechanistic analysis revealed a potential role of Resf1 in transcriptional control through association with compound G4 quadruplexes in expressed sequences, particularly those associated with ribosomal biogenesis. These results suggest that loss of Resf1 enhances tumor progression in ER- breast cancer through multiple alterations in both transcriptional and translational control. Metastasis is the major cause of breast cancer deaths. However, unlike the primary tumor, acquired mutations do not appear to play a significant role in the development of metastatic disease. A person's individual ancestry, however, does significantly influence metastatic efficiency. Our laboratory therefore seeks to identify and characterize the differences in inherited genes that increase or decrease metastatic burden. One inherited gene that changes metastatic efficiency is the poorly characterized gene Resf1. This gene encodes a large protein that has very little predicted structure. Reduction or loss of Resf1 accelerates tumor growth and increases the incidence and extent of metastatic tumors in the lung. Analysis here suggests that Resf1 protein is associated with DNA sequences that can form a DNA "knot"-like structure known as a G4 quadruplex. The association of Resf1 with these structures may be influencing the ability of tumor cells to undergo the epithelial-to-mesenchymal transition, which is thought to be critical for metastatic progression. Reduction or loss of Resf1 may therefore be accelerating the terminal steps of breast cancer progression.