Transcriptional regulation of parathyroid hormone-related protein promoter P2 by NF-κB in adult T-cell leukemia/lymphoma

Abstract

Parathyroid hormone-related protein (PTHrP) plays a primary role in the development of humoral hypercalcemia of malignancy (HHM) that occurs in the majority of patients with adult T-cell leukemia/lymphoma (ATLL) due to human T-cell lymphotropic virus type-1 (HTLV-1) infection. We previously showed that ATLL cells constitutively express high levels of PTHrP via activation of promoters P2 and P3, resulting in HHM. In this study, we characterized a nuclear factor-jB (NF-jB) binding site in the P2 promoter of human PTHrP. Using electrophoretic mobility shift assays, we detected a specific complex in Taxexpressing human T cells composed of p50/c-Rel, and two distinct complexes in ATLL cells consisting of p50/p50 homodimers and a second unidentified protein(s). Chromatin immunoprecipitation assays confirmed in vivo binding of p50 and c-Rel on the PTHrP P2 promoter. Using transient co-transfection with NF-jB expression plasmids and PTHrP P2 luciferase reporter-plasmid, we showed that NF-jB p50/p50 alone and p50/ c-Rel or p50/Bcl-3 cooperatively upregulated the PTHrP P2 promoter. Furthermore, inhibition of NF-jB activity by Bay 11-7082 reduced PTHrP P2 promoter-initiated transcripts in HTLV-1-infected T cells. In summary, the data demonstrated that transcriptional regulation of PTHrP in ATLL cells can be controlled by NF-jB activation and also suggest a Taxindependent mechanism of activation of PTHrP in ATLL.

A Novel Bioluminescent Mouse Model and Effective Therapy for Adult T-Cell Leukemia/Lymphoma

“…5 Although PTHrP is likely very important in ATLL, the concentrations of PTHrP in the serum do not always correlate with the degree of hypercalcemia in ATLL patients, suggesting that other factors are involved in the development of HHM. In our study, we carried out real-time RT-PCR and ELISA and found high expression of MIP-1a in RV-ATL cells and increased MIP-1a in the plasma of mice bearing RV-ATL-luc cells.…”

“…In addition, NF-nB binding sites were found in the promoters of parathyroid hormone-related protein (PTHrP; refs. 5,6) and macrophage inflammatory protein 1a (MIP-1a; ref. 7).…”

Haematological emergencies managing hypercalcaemia in adults and children with haematological disorders

“…Evidence of trans ‐activation of the promoter of the PTHLH gene was demonstrated in a plasmid‐construct transfection model (Watanabe et al , 1990). More recently it was demonstrated that nuclear factor kappa B (NF‐κB) can upregulate PTHLH transcription in ATLL cells by a tax ‐independent mechanism (Nadella et al , 2007).…”

Methylation of specific CpG sites in the P2 promoter ofparathyroid hormone-related proteindetermines the invasive potential of breast cancer cell lines

“…In adult T cell leukemia/lymphoma (ATLL) it was shown that the PTHrP promoter 2, which is upregulated in ATLL as well, contains a binding site for nuclear factor κB (NFκB), to which the subunits p50 and c-Rel bind in vivo. 35 Transient co-transfection with NFκB expression plasmids and PTHrP P2 luciferase reporterplasmid, showed that different combinations of the subunits cooperatively upregulated the PTHrP P2 promoter, while inhibition of NFκB activity reduced PTHrP P2 promoter-initiated transcription indicating a crucial role for NFκB in the regulation of the P2 in ATLL. It remains to be demonstrated if a similar mechanism can also account for the observed activation of P2 correlating with the invasiveness of our breast cancer cell line model.…”