Fig. 2.

PTHrP effects on DNA synthesis and proliferation. A: stable clones of PTHrP-positive and PTHrP-negative H1944 cells were assayed for rate of DNA synthesis by incubation with [³H]thymidine. The PTHrP-positive cells incorporated thymidine into DNA at 43 ± 7% of the rate demonstrated by PTHrP-negative clones. **P < 0.01. N = 5 PTHrP clones and 4 vector-transfected clones. B: cells were incubated with 10 μM bromodeoxyuridine (BrdU) for 2 or 24 h and analyzed for BrdU content by flow cytometry. PTHrP expression reduced the percentage of cells that were BrdU positive by at least one-half at both time points. Data represent results from 3 clones each for the control and experimental groups. *P < 0.05 vs. vector. C: growth was assessed by MTT assay in PTHrP-producing and nonproducing H1944 cells plated in 96-well plates at 4,000 cells/well. The PTHrP-positive cells grew at ∼50% of the rate of the vector-transfected cells. The data represent results from 5 vector clones and 4 PTHrP clones. *P < 0.05 and **P < 0.01 vs. vector.