PLAUR and infection: By contrast, uPAR -/- mouse embryonic fibroblasts (MEFs) grow faster than wt MEFs and infection with a uPAR-containing retrovirus decreases their growth rate; proliferation of wt MEFs appears do not involve FPRs or integrins [93], which instead may contribute to the proliferative advantage observed in the other reports [91,92], suggesting different regulatory mechanisms in MEFs.