HYAL1 and breast carcinoma: On the other hand, similarly to HAS, hyaluronidase exhibited a completely opposite effect in some cases; a human breast cancer transplanted into immunodeficient (SCID) mice markedly regressed after intravenous administration of testicular hyaluronidase [94], and HYAL-1 overexpression in a colorectal cancer model inhibited tumor formation [95].