This 21-amino acid peptide corresponds to residues 253-273 of human cytochrome P450 CYP3A4. Cytochrome P450, a family of over a thousand different members, is involved the metabolism of a wide variety of both endogenous and foreign compounds, in drug and toxin removal. In insects, xenobiotic metabolism is known to involve members of the CYP6 family of cytochrome P450s. Cytochromes P450 are thought to facilitate tumor invasion and metastasis by the generation of reactive oxygen species during various metabolic steps and by the activation of protein kinases, cellular proteoglycan changes, and lysosomal enzymes. High cytochrome P450 CYP3A4/5 expression may predict metastasis and poor prognosis in osteosarcomas. Its use as a biomarker of therapeutic response will have implications for the treatment of these tumors.

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