DRD4 and cancer: For instance, both breast and CRC patients with elevated DRD4 expression exhibit poor prognosis.[24, 31, 32] In nervous system tumors and breast cancer, DRD4 functions as an oncogene that promotes tumor cell proliferation and metastasis.[21, 24, 33] However, the elevated expression of DRD4 exhibits tumor‐suppressive functions in certain cancers.