Consistent downregulation of human lactoferrin gene, in the common eliminated region 1 on 3p21.3, following tumor growth in severe combined immunodeficient (SCID) mice.

Lactoferrin (LF) is one of 19 active genes in the common eliminated region 1 at 3p21.3 identified by us. LF was transfected into mouse fibrosarcoma A9. Fourteen severe combined immunodeficient (SCID) derived tumors from two PI based artificial chromosome (PAC)-transfectants containing the entire LF gene and two LF-cDNA transfectants were analyzed by real time polymerase chain reaction at the DNA and RNA level. Following SCID tumor passage, LF expression was decreased or eclipsed, in all tumors although DNA levels did not change considerably. Promoter methylation and/or rearrangement of the insertion site may be responsible for human LF downregulation in mouse fibrosarcoma derived tumors.