NF-kappaB2 processing and p52 nuclear accumulation after androgenic stimulation of LNCaP prostate cancer cells.

Several reports suggest that androgen signalling interferes with canonical RelA-p50 activity in androgen-sensitive cells. Whether this also occurs with non-canonical NF-kappaB subunits has not been studied. Here we report that androgenic stimulation of LNCaP cells with the androgen analogue R1881 appears to positively regulate the non-canonical NF-kappaB pathway as p52 accumulates both in the cytoplasm and nucleus after 48-72 h of stimulation. In contrast to TNF-alpha stimulation, androgen stimulation fails to induce RelB expression and is absent from nucleus of R1881-treated LNCaP cells. Electromobility shift assays reveal a time-dependent change in the nature of NF-kappaB complexes actively bound to DNA after 72 h of androgenic stimulation concomitant with the appearance of p52-containing complexes. Co-immunoprecipitation studies indicate that newly produced p52 can exist as a heterodimer with RelA or p50, but may be mainly present as a homodimer. RNAi experiments targeting IKK-alpha and IKK-beta show that the R1881-induced nuclear accumulation of p52 is IKK-alpha-dependent. These results point to a novel mechanism by which androgens regulate NF-kappaB and provide a rationale for further studies into the biological significance of non-canonical NF-kappaB signalling in prostate cancer.