Effects of bisphosphonates on human esophageal squamous cell carcinoma cell survival

Advanced esophageal cancer with bone metastases: Prognostic biomarkers and palliative treatment

Esophageal cancer (EC) is a common and devastating tumor of the upper digestive tract. Unfortunately, by the time any symptoms have manifested, the disease has often progressed to an advanced stage and is accompanied by macro- and micrometastases, including in the bones. The treatment of esophageal cancer with bone metastases remains clinically challenging, given the poor prognosis associated with this condition. Effective prognostic biomarkers can help medical staff choose the appropriate operation and treatment plan, that is for most beneficial for making patients. Current treatments for esophageal cancer with bone metastases include pain-relieving drugs, surgical therapy, radiotherapy (RT), chemotherapy (CT, including molecular-targeted drug therapy), endocrine therapy (ET), bisphosphonates (BPs) and interventional therapy. Of these robust measures, radiotherapy has emerged as a particularly promising therapy for bone metastases from esophageal cancer. Substantial progress has been made in radiation therapy techniques since the discovery of X-rays by Roentgen in 1895. In its palliative capacity, the key goals of radiotherapy are to relieve the patients' bone pain and debilitate effects, including relieving spinal cord compression, correcting the spinal deformity and restoring spinal stability. However, it is worth mentioning that RT for esophageal cancer has various side effects. Currently, the available studies focused exclusively on radiotherapy for ECBM are too small to draw any definitive conclusions, and each of these studies has significant limitations. In this review, in addition to the epidemiology described at the beginning, we will explore the current prognostic biomarkers and radiotherapy for esophageal cancer, with a particular focus on those with bone metastases.

Upregulation of mmu_circ_0001066 attenuates the inhibitory effect of bisphosphonates on osteoclastogenesis

OBJECTIVE

Medication-related osteonecrosis of the jaw (MRONJ) is the main adverse side effect of bisphosphonates (BPs), mainly owing to the inhibitory effect of BPs on osteoclastogenesis. CircRNAs were identified to be an important factor in regulating cellular processes. The aim of this study was to explore the effect of mmu_circ_0001066 on BP-inhibited osteoclastogenesis.

MATERIALS AND METHODS

The expression of MRONJ-related miRNA in RANKL-induced RAW264.7 cells treated with BP was analyzed using qRT-PCR analysis. Bioinformatics techniques were applied to screen potential circRNAs. Tartrate-resistant acid phosphatase (TRAP) staining and bone resorption assays were used to examine the effect of mmu_circ_0001066 on osteoclastogenesis. Bioinformatics analysis, luciferase reporter assays, and Western blotting assays were performed to investigate the underlying mechanism.

RESULTS

Four MRONJ-related miRNAs were upregulated in BP-treated RAW264.7 cells, and the expression of mmu_circ_0001066 was negatively correlated with those of MRONJ-related miRNAs. Furthermore, the upregulation of mmu_circ_0001066 partially attenuated the inhibitory effect of BP on osteoclastogenesis in RAW264.7 cells. Mechanistically, upregulated miR-16 suppressed osteoclastogenesis and miR-16 inhibitor increased osteoclastogenesis. Furthermore, we have identified that miR-16 is a downstream effector of mmu_circ_0001066.

CONCLUSION

Our results suggest that mmu_circ_0001066 played an important role in the BP-mediated suppression of osteoclastogenesis, which lays a foundation for identifying mmu_circ_0001066 as a potential biomarker for MRONJ.

Histone deacetylase inhibitors sensitize 5-fluorouracil-resistant MDA-MB-468 breast cancer cells to 5-fluorouracil

Resistance to 5-fluorouracil (5-FU) is a serious problem in cancer therapy and overcoming it is required in order to improve the efficacy of cancer chemotherapy. Histone deacetylase (HDAC) inhibitors are used in cancer treatments and, recently, it has been reported that HDAC inhibitors can overcome resistance to various anti-cancer drugs in vitro. In the present study, a 5-FU-resistant breast cancer cell line was established, and the effects of HDAC inhibitors in these cells were examined. The 5-FU-resistant cell line MDA-MB-468 (MDA468/FU) was established by continuous exposure of the parental cells to 5-FU. This subline was characterized by high resistance to 5-FU, higher mRNA expression levels of thymidylate synthetase and dihydropyrimidine dehydrogenase (DPD), and lower mRNA expression levels of uridine monophosphate synthetase (UMPS) than the parental cells. Gimeracil, a DPD inhibitor, did not affect the sensitivity of MDA468/FU cells to 5-FU. Oteracil, a UMPS inhibitor, decreased the cytotoxicity of 5-FU in MDA468 cells, but not in MDA468/FU cells. The HDAC inhibitors, valproic acid and suberanilohydroxamic acid sensitized the two cell lines to 5-FU in a concentration-dependent manner. In conclusion, the results of the present study revealed that HDAC inhibitors increase the sensitivity to 5-FU in 5-FU-sensitive and -resistant cells.

Augmentation of the cytotoxic effects of nitrogen-containing bisphosphonates in hypoxia

OBJECTIVES

Tumour hypoxia is a major obstacle in cancer therapy that leads to poor prognosis. Therefore, the development of cancer treatments that are effective in hypoxia is necessary. Nitrogen-containing bisphosphonates (N-BPs), which are used to treat bone disease, are cytotoxic to several cancer cells in normoxia. Therefore, we investigated the cytotoxicity of N-BPs in cancer cells in hypoxia.

METHODS

We studied the cytotoxicities of N-BPs, statins and anticancer drugs in human cancer cells under hypoxic conditions (1% O₂ ). The expression levels of enzymes in the mevalonate pathway in hypoxia were measured by real-time reverse transcription polymerase chain reaction and Western blotting.

KEY FINDINGS

In hypoxia, cell growth inhibition by 5-fluorouracil and cisplatin was not changed as compared to that in normoxia; however, cell growth inhibition by N-BPs and via zoledronate-induced apoptosis was higher in hypoxia than that in normoxia. Furthermore, geranylgeraniol completely inhibited the growth inhibitory effects of zoledronate. Additionally, the mRNA and protein levels of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase significantly decreased in hypoxia. Moreover, simvastatin potentiated the growth inhibitory effect of zoledronate.

CONCLUSIONS

The cytotoxicity of N-BPs, but not 5-fluorouracil and cisplatin, is potentiated in hypoxia, through the loss of HMG-CoA reductase function. N-BPs may be effective against cancer in normoxia and hypoxia.