ALK⁺ALCL cells secrete MMP-9, which enhances IL-8 mRNA expression by keratinocytes through PAR-2 and NF-κB activation. (A) IL-8 mRNA levels were evaluated by qRT-PCR on PAR-2– or control siRNA–transfected HaCaT cells cultured in DMEM supplemented with (+) or without (−) rhMMP-9. (B) HaCaT cells exposed to culture supernatant from Karpas-299 (Karpas) and SU-DHL-1 cells supplemented with 10μM (+) or without (−) MMP inhibitor (GM6001) for 24 hours were collected and IL-8 mRNA measured by qRT-PCR. Results are expressed as the mean ± SD of 3 independent experiments done in triplicate. ***P < .001 by Student t test. (C) Western blotting was performed with anti–NF-κB p65 and anti–phospho-Ser⁵³⁶ NF-κB p65 Abs to determine NF-κB activation in keratinocytes (HaCaT cell line) under the influence of culture supernatant from Karpas-299 cells supplemented with (+) or without (−) GM6001. β-actin was used as a loading control.