OBJECTIVETo study the demethylation effect of arsenic trioxide (As2O3) on ERα-negative human breast cancer MDA-MB-435s cells and its possible mechanisms, and to observe its treatment efficacy in combination with tamoxifen (TAM) after ERα re-expression.

METHODSMTT assay was used to examine the inhibitory effect of As2O3 treatment alone or in combination with TAM on cell proliferation. A nude mouse xenograft model was used to further examine the treatment efficacy in vivo. MSP was used to detect the methylation status of ERα gene after treated with As2O3 in MDA-MB-435s cells and the transplanted tumor tissues. RT-PCR was used to detect the mRNA expression of DNMT1 and Erα. Western bolt was used to detect the DNMT1 and ERα protein expression. The diameter of xenograft tumors was measured weekly, and the tumor growth curve was drawn.

RESULTSThe level of proliferation of the MDA-MB-435s cells was significantly suppressed after treatment with different concentration of As2O3 alone or As2O3 combined with TAM, and the 4 µmol/L As2O3 + TAM treatment for 72 h showed the highest inhibition rate (62.6%). 1, 2, 4 µmol/L As2O3 had demethylation effect on MDA-MB-435s cells, and the DNMT1 mRNA and protein expression was inhibited and accompanied by ERα mRNA and protein re-expression. The unmethylation specific bands of ERα gene were enhanced after treated by As2O3 alone or As2O3 combined with TAM in the xenograft tumors. The expression of DNMT1 mRNA and protein was inhibited, and accompanied by ERα mRNA and protein re-expression. An significant decrease of volume and weight of the xenograft tumors in the As2O3 treated alone or combined with TAM groups was observed compared with those of the normal saline group or TAM alone group (P < 0.05), and the 4 mg/kg As2O3 + TAM group had the highest inhibition rate of tumor weight (79.5%) and volume (76.4%).

CONCLUSIONSERα can be re-expressed in ERα-negative breast cancer MDA-MB-435s cells after treated with As2O3 by inhibiting the DNMT1 activity. MDA-MB-435s cells are re-sensitized to endocrine therapy after ERα re-expression. As2O3 combined with TAM may provide a new therapeutic approach for patients with ERα-negative breast cancer in the clinic.

Animals ; Antineoplastic Agents ; administration & dosage ; pharmacology ; Antineoplastic Agents, Hormonal ; administration & dosage ; Antineoplastic Combined Chemotherapy Protocols ; pharmacology ; Arsenicals ; administration & dosage ; pharmacology ; Breast Neoplasms ; genetics ; metabolism ; pathology ; Cell Line, Tumor ; Cell Proliferation ; drug effects ; DNA (Cytosine-5-)-Methyltransferase 1 ; DNA (Cytosine-5-)-Methyltransferases ; DNA Methylation ; Dose-Response Relationship, Drug ; Estrogen Receptor alpha ; genetics ; metabolism ; Female ; Humans ; Mice ; Mice, Inbred BALB C ; Mice, Nude ; Oxides ; administration & dosage ; pharmacology ; RNA, Messenger ; metabolism ; Tamoxifen ; administration & dosage ; Tumor Burden ; drug effects ; Xenograft Model Antitumor Assays

BACKGROUND/AIMS: BK virus (BKV) has been associated with late-onset hemorrhagic cystitis (HC) in recipients of hematopoietic stem cell transplantation (HSCT). Cidofovir has been used at higher doses (3 to 5 mg/kg/wk) with probenecid prophylaxis; however, cidofovir may result in nephrotoxicity or cytopenia at high doses. METHODS: Allogeneic HSCT recipients with BKV-associated HC are treated with 1 mg/kg intravenous cidofovir weekly at our institution. A microbiological response was defined as at least a one log reduction in urinary BKV viral load, and a clinical response was defined as improvement in symptoms and stability or reduction in cystitis grade. RESULTS: Eight patients received a median of 4 weekly (range, 2 to 11) doses of cidofovir. HC occurred a median 69 days (range, 16 to 311) after allogeneic HSCT. A clinical response was detected in 7/8 patients (86%), and 4/5 (80%) had a measurable microbiological response. One patient died of uncontrolled graft-versus-host disease; therefore, we could not measure the clinical response to HC treatment. One microbiological non-responder had a stable BKV viral load with clinical improvement. Only three patients showed transient grade 2 serum creatinine toxicities, which resolved after completion of concomitant calcineurin inhibitor treatment. CONCLUSIONS: Weekly intravenous low-dose cidofovir without probenecid appears to be a safe and effective treatment option for patients with BKV-associated HC.
Administration, Intravenous ; Adult ; Antiviral Agents/*administration & dosage/adverse effects ; BK Virus/*drug effects/immunology ; Cystitis/diagnosis/*drug therapy/immunology/virology ; Cytosine/administration & dosage/adverse effects/*analogs & derivatives ; Drug Administration Schedule ; Female ; Hematopoietic Stem Cell Transplantation/*adverse effects ; Humans ; Immunocompromised Host ; Male ; Organophosphonates/*administration & dosage/adverse effects ; Polyomavirus Infections/diagnosis/*drug therapy/immunology/virology ; Retrospective Studies ; Time Factors ; Transplantation, Homologous ; Treatment Outcome ; Tumor Virus Infections/diagnosis/*drug therapy/immunology/virology ; Viral Load