Disulfiram sensitizes pituitary adenoma cells to temozolomide by regulating O6-methylguanine-DNA methyltransferase expression

Abstract

O6-methylguanine-DNA methyltransferase (MGMT) activity is responsible for temozolomide (TMZ) resistance in patients harboring aggressive pituitary adenomas. Recently, disulfiram (DSF) has been shown to induce the loss of MGMT protein and increase TMZ efficacy in glioblastoma cells, while CD133+ nestin+ cells isolated from the cell population have been implicated as pituitary adenoma stem-like cells. However, whether DSF is able to potentiate the cytotoxic effects of TMZ on human pituitary adenoma cells has not been investigated to date. In the present study, CD133+ nestin+ phenotype cells were isolated from primary cultured human pituitary adenoma cells using microbeads. It was found that DSF reduced MGMT protein expression and sensitized human pituitary adenoma cells and stem-like cells to TMZ in vitro, while the proteasome inhibitor PS-341 abrogated the inhibitory effect of DSF on MGMT in vitro. The sensitizing effect of DSF was also verified in primary cultured human pituitary adenoma cells in vivo. The results of the present study suggested that DSF can increase the efficacy of the anti-tumor effect of TMZ on human pituitary adenoma cells and CD133+ nestin+ stem like cells via the ubiquitin-proteasomal MGMT protein elimination route. DSF combined with TMZ may be an effective therapeutic strategy against aggressive pituitary adenomas.

Experimental Evidence and Clinical Implications of Pituitary Adenoma Stem Cells

“…The resulting single tumor displayed low proliferation rate (as for Ki67 labeling), histology resembling PA structure, and expressed synatpophysin, but it was not further characterized. Similar results were obtained by the intracranial injection in nude mice of 10,000 CD133 + /nestin + PA cells, which gave rise to tumors, detectable after 6 weeks from the graft (83). In another study, one PASC culture from a null PA, sorted for CD15 expression, was pseudo-orthotopically injected in the brain of three mice (84).…”

“…A similar approach was described by Zhao et al who sorted CD133 + and NESTIN + co-expressing cells from dispersed PA cells. These cells represented up to the 3% of total PA cells and were able to generate spheres for several passages (83). In other reports, stem cell-permissive medium allowed the selection of sphere-forming cells in cultures from all the 12 (71) or 14 (84) tumor analyzed including GH-, ACTH-, FSH/PRLsecreting PAs and NFPAs.…”

“…Accordingly, Xu et al reported that PASCs from a GHoma were insensitive to both carboplatin and etoposide (69) and temozolomide resistance was described in another study (66). Interestingly, in a drug repositioning study, in vitro and in vivo treatment with disulfiram, a clinically approved drug for the treatment of alcoholism, sensitizes CD133 + /nestin + PASCs to temozolomide cytotoxicity, preventing drug-induced DNA damage repair by inhibiting O-6-methylguanine-DNA methyltransferase expression (83). Although CSC resistance to cytotoxic drugs is still a relevant issue in the treatment of all types of tumor, including aggressive PAs, PASCs might retain sensitivity to biological treatments.…”

Estrogen receptor α/prolactin receptor bilateral crosstalk promotes bromocriptine resistance in prolactinomas

“…Human pituitary adenoma tissues were processed directly following surgery, and according to the standard protocols described in our previous study 20 . The Human Tumor Dissociation kit (Miltenyi Biotec.…”

“…no. MB106970-T46) as previously described 20 , 21 . The QuadroMACS™ Separation Unit (Miltenyi Biotec) was used for isolation.…”