To evaluate the relevance of ADRB3 gene in promotion of tumor growth in immune competent mice, we crossed ADRB3-/- mice with the MMTV-PyMT transgenic mice, a mouse model of breast cancer that mirrors the multistep progression of human breast cancers, and generated female cohorts with the genotypes of PyMT-ADRB3+/+ mice and PyMT-ADRB3-/- mice. The gene discussed is ADRB3; the disease is breast cancer.