Figure 2.

Parathyroid hormone-related protein mRNA expression is reduced by EGFR inhibitors and increased by the addition of exogenous EGFR ligands. (A) RWGT2 cells were treated with 1 μM PD for 6 h, a neutralising polyclonal antibody to AREG (10 μg ml⁻¹), a ligand blocking EGFR antibody (αEGFR, 10 μg ml⁻¹) or PBS (C) for 24 h. Neutralising antibodies to growth factors are represented by the symbol (α). The mRNA was harvested from four independent cultures and analysed by QRT-PCR. PD, P=0.03; αAREG, P=0.05. (B) HARA cells were treated with 1 μM PD for 6 h or a neutralising polyclonal antibody to AREG (10 μg ml⁻¹) or PBS (C) for 24 h. The mRNA was harvested from four independent cultures and analysed by QRT-PCR. PD, P=0.017; αAREG, P=0.034. (C) RWGT2 cells were incubated with PBS (C), 100 ng ml⁻¹ of EGF or 1 mg ml⁻¹ of AREG for 2, 4 and 6 h. The mRNA was harvested from four independent cultures and analysed by QRT-PCR. Two-hour EGF, P=0.02; 4 h EGF, P=0.002; 4 h AREG, P=0.002; 6 h EGF, P=0.004; 6 h AREG, P=0.001. (D) HARA cells were incubated with PBS (C), 100 ng ml⁻¹ of EGF or 1 mg ml⁻¹ of AREG for 2, 4 and 6 h. The mRNA was harvested from four independent cultures and analysed by QRT-PCR. Four-hour AREG, P=0.02; 6 h EGF, P=0.02; 6 h AREG P=0.013. Values in all panels represent the mean of four samples from individual cultures±s.e.m. These experiments were repeated three times with cells derived from independent passages with similar results, ^*P<0.05 relative to C (control). Two-tailed Student's t-test.