FIGURE 7.

Dual upregulation of hnRNP-E1 and FRs at the posttranscriptional level in HeLa-IU₁–derived tumor xenografts of mice fed either a folate-replete diet (A and C) or a folate-deficient diet (B and D) for 1 mo before and after implantation of 1 million HeLa-IU₁ cells into their flanks. Because of prohibitive costs, this longitudinal experiment was carried out only once; similar results were obtained from 2 randomly selected tumors each from folate-replete mice (n = 6) and folate-deficient mice (n = 5). Immunohistochemistry for hnRNP-E1 with the use of nonimmune serum (A and B) compared with anti–hnRNP-E1 antiserum (C and D). Magnification was 40×. Western blots (50-μg tumor protein probed with either anti-folate receptor antiserum, anti–hnRNP-E1 antiserum, or anti-GAPDH antibodies) to assess the expression of folate receptor and hnRNP-E1 in the tumor (E). Densitometric evaluation of folate receptor and hnRNP-E1 protein signals in relation to GAPDH is shown below the gels. Northern blots (20 μg total tumor RNA) to assess FR α mRNA and hnRNP-E1 mRNA in tumor xenografts (F). Densitometric scanning of the signals from northern blots was adjusted by a loading control (β-actin) and is shown below the gel. The HF diet contained 1200 nmol folate/kg; the LF diet contained 400 nmol folate/kg. FR, folate receptor; hnRNP-E1, heterogeneous nuclear ribonucleoprotein E1.