Tumors derived from breast epithelial cells transformed with HRASG12V oncogene cause significant skeletal muscle defects. A, Metastatic breast cancers show significant genomic aberrations in four RAS proto-oncogenes. B, Growth rate of tumors derived from three cell lines—TKTB34-RAS, TKTB6-RAS, and TKTB34-PIK3CA. A total of 1 × 106 cells were injected to the mammary fat pad. C, RAS protein levels in transformed cell lines. D, Impaired rotarod performance were observed in mice bearing tumors from RAS transformed cells. E, Mutant RAS oncogene-derived tumors but not mutant PIK3CA-derived tumors caused reduction in skeletal muscle contraction force. F, Tumors derived from TKTB34-RAS, which expressed higher levels of HRASG12V than TKTB6-RAS, caused severe loss of grip strength. G, Tumors derived from TKTB34-RAS transformed cells caused reduction in EDL muscle weight.
ARTICLE ABSTRACT
Cancer-induced skeletal muscle defects differ in severity between individuals with the same cancer type. Cancer subtype-specific genomic aberrations are suggested to mediate these differences, but experimental validation studies are very limited. We utilized three different breast cancer patient-derived xenograft (PDX) models to correlate cancer subtype with skeletal muscle defects. PDXs were derived from brain metastasis of triple-negative breast cancer (TNBC), estrogen receptor–positive/progesterone receptor–positive (ER+/PR+) primary breast cancer from a BRCA2-mutation carrier, and pleural effusion from an ER+/PR− breast cancer. While impaired skeletal muscle function as measured through rotarod performance and reduced levels of circulating and/or skeletal muscle miR-486 were common across all three PDXs, only TNBC-derived PDX activated phospho-p38 in skeletal muscle. To further extend these results, we generated transformed variants of human primary breast epithelial cells from healthy donors using HRASG12V or PIK3CAH1047R mutant oncogenes. Mutations in RAS oncogene or its modulators are found in approximately 37% of metastatic breast cancers, which is often associated with skeletal muscle defects. Although cells transformed with both oncogenes generated adenocarcinomas in NSG mice, only HRASG12V-derived tumors caused skeletal muscle defects affecting rotarod performance, skeletal muscle contraction force, and miR-486, Pax7, pAKT, and p53 levels in skeletal muscle. Circulating levels of the chemokine CXCL1 were elevated only in animals with tumors containing HRASG12V mutation. Because RAS pathway aberrations are found in 19% of cancers, evaluating skeletal muscle defects in the context of genomic aberrations in cancers, particularly RAS pathway mutations, may accelerate development of therapeutic modalities to overcome cancer-induced systemic effects.
Mutant RAS- and PIK3CA-driven breast cancers distinctly affect the function of skeletal muscle. Therefore, research and therapeutic targeting of cancer-induced systemic effects need to take aberrant cancer genome into consideration.
