CRH and neoplasm: However, administration of Bufonis venenum promoted the β-endorphin and corticotropin-releasing factor (CRF) levels in plasma, and immunostaining of β-endorphin and μ-opioid receptors in the tumor xenograft tissues of paw cancer pain mice; treatment with Bufonis venenum also stimulated the expression of β-endorphin and CRF in cultured primary lymphocytes [9, 10].