Radiosensitizing effect of zoledronic acid in small cell lung cancer

The effects of bisphosphonate and radiation therapy in bone-metastatic lung adenocarcinoma: the impact of KRAS mutation

Background

KRAS mutation is the most common genetic alteration in lung adenocarcinoma (LADC) in Western countries and is associated with worse outcome in bone-metastatic cases. Yet, to date, no effective treatment guidelines were developed for these patients. Accordingly, our aim was to investigate the impact of KRAS mutation on bisphosphonate (BTx) and radiation therapy (RTx) in bone-metastatic LADC patients.

Methods

Clinicopathological variables of 134 consecutive LADC patients with bone metastases at diagnosis and known KRAS status were retrospectively analyzed. The effects of BTx, RTx and KRAS mutation on overall survival (OS) were investigated.

Results

Of the total cohort, 93 patients were identified as KRAS wild-type (WT) (69.4%) and 41 (30.6%) as KRAS mutant patients. The presence of KRAS mutation was associated with significantly reduced median OS (5.1 vs. 10.2 months in KRAS WT patients; P=0.008). Irrespective of KRAS mutational status both BTx (P=0.007) and RTx (P=0.021) conferred a significant benefit for OS. Notably, however, when analyzing the patients with KRAS-mutant and KRAS WT tumors separately, the benefit from BTx and RTx on OS remained statistically significant only in KRAS WT patients (P=0.032 and P=0.031, respectively).

Conclusions

KRAS mutation is a strong negative prognostic factor in bone-metastatic LADC patients. Both BTx and RTx can increase the OS with a pronounced benefit for patients with KRAS WT tumors. Altogether, KRAS mutational status should be considered during therapeutic decision making in bone-metastatic LADC patients.

Zoledronic acid exhibits radio-sensitizing activity in human pancreatic cancer cells via inactivation of STAT3/NF-κB signaling

Background: Although pancreatic cancer is typically radio-sensitive, local treatment failure and metastasis are commonly caused by the development of resistance to radiotherapy. In the current study, the radio-sensitizing actions of zoledronic acid (ZOL) on pancreatic cancer cells were investigated.

Materials and methods: Three human pancreatic cancer cell lines were exposed to ZOL, ionizing radiation (IR), or a combination of both, and the effects of the respective drug regimens on cell proliferation and invasion were examined.

Results: Combined treatment with low doses of ZOL plus IR efficiently increased cell death and attenuated cell invasion compared with the individual use of ZOL or IR. These effects of ZOL were associated with inactivation of signal transducer and activator of transcription 3 (STAT3) and nuclear factor-κB (NF-κB).

Conclusion: Collectively, these data suggest that ZOL in combination with IR is a promising therapeutic strategy for enhancing radio-sensitivity in pancreatic cancer cells via downregulation of the STAT3/NF-κB signaling pathway.

Zoledronic acid is an effective radiosensitizer in the treatment of osteosarcoma

To overcome radioresistance in the treatment of osteosarcoma, a primary malignant tumor of the bone, radiotherapy is generally combined with radiosensitizers. The purpose of this study was to investigate a third-generation bisphosphonate, zoledronic acid (ZOL), as a radiosensitizer for osteosarcoma. We found that exposure of KHOS/NP osteosarcoma cells to 20 μM ZOL decreased the γ-radiation dose needed to kill 90% of cells. This radiosensitizing effect of ZOL was mediated through decreased mitochondrial membrane potential, increased levels of reactive oxygen species, increased DNA damage (as assessed by counting γ-H2AX foci), decreased abundance of proteins involved in DNA repair pathways (ATR, Rad52, and DNA-PKcs), and decreased phosphorylation of PI3K-Akt and MAPK pathway proteins (Raf1, MEK1/2, ERK1/2, and Akt), as compared to γ-irradiation alone. Cells treated with ZOL plus γ-irradiation showed impaired cell migration and invasion and reduced expression of epithelial-mesenchymal transition markers (vimentin, MMP9, and Slug). In Balb/c nude mice, the mean size of orthotopic osteosarcoma tumors 2 weeks post-inoculation was 195 mm³ following γ-irradiation (8 Gy), while it was 150 mm³ after γ-irradiation plus ZOL treatment (0.1 mg/kg twice weekly for 2 weeks). These results provide a rationale for combining ZOL with radiotherapy to treat osteosarcoma.

Zoledronic acid augments the radiosensitivity of cancer cells through perturbing S- and M-phase cyclins and p21CIP1 expression

Radiotherapy and adjuvant chemotherapy have become the standard treatments for multiple types of cancer. Although cancer cells are usually sensitive to radiotherapy, metastasis and local failure still occur mainly due to developed resistance to radiotherapy. Thus, it is critical to improve therapeutics for cancer treatment. The present study demonstrated that third-generation bisphosphonate zoledronic acid (ZOL), even at a low concentration, augments the radiosensitivity of cancer cells exposed to ionizing radiation (IR) by inducing S-phase arrest and subsequently promoting apoptosis. This function of ZOL was associated with elevated levels of cyclin A and cyclin B in the S and M phases, as well as decreased p21^CIP1 expression. In addition, ZOL also inhibited malignant the invasiveness of cancer cells. Notably, these effects could be enhanced concurrently with IR. The present data indicated that combined treatment with ZOL plus IR may be a novel technique to augment the radiosensitivity of cancer cells.

Toxicity of a dental adhesive compared with ionizing radiation and zoledronic acid

Background

To determine the toxicity of aqueous dilutions of a universal self-priming dental adhesive (DA) and comparing these with those elicited by exposure to ionizing radiation (IR), Zoledronic acid (Z) treatment and the synergic effects of the combined treatment with IR+Z.

Material and Methods

The genotoxic effect of DA was determined by the increase in the frequency of micronuclei in cytokinesis-blocked in cultured human lymphocytes before and after exposure to 2Gy of X-rays. The cytotoxic effect was studied by using the MTT cell viability test in normal prostate cell lines (PNT2) after exposure to different X-ray doses (0Gy-20Gy). The cell lines divided into different groups and treated with different test substances: DA in presence of O2, DA in absence of O2, Z-treated and control.

Results

An in vitro dose-dependent and time-dependent cytotoxic effect of DA, Z and IR on PNT2 cells (p>0.001) was demonstrated. DA without-O2, following the recommendations of manufacturers, had a more pronounced effect of increasing cell death than DA with-O2 (p<0.001). In the genotoxicity assay, DA at 25% of its original concentration significantly increased chromosome damage (p<0.001). The samples studied were found to be toxic, and the samples photo-polymerized in absence of O2 showed a bigger cytotoxic effect comparable to the additive toxic effect showed by the combined treatment of IR+Z.

Conclusions

Additional effort should be carried out to develop adhesives, which would reduce the release of hazardous substances; since toxic effects are similar to that reported by other agents whose clinical use is controlled by the health authorities.

Key words: Micronucleus, toxicity, dental adhesive, zolendronic acid, radiation effects.

Zoledronic acid and irradiation in oral squamous cell carcinoma

OBJECTIVE

This in vitro study evaluated cytotoxicity and cell migration effects of zoledronic acid and irradiation upon oral squamous cell carcinoma.

MATERIALS AND METHODS

Zoledronic acid was administrated at doses of 10, 25, 50, and 100 μM to PE/CA-PJ15 oral squamous cell carcinoma cultures, irradiated with different doses (0, 5, 15, and 30 Gy), followed by evaluation of the effects on cell viability. Cell migration capacity was studied after 24- and 72-h incubation.

RESULTS

At 24 h, the 100 μM concentration of zoledronic acid combined with 15 Gy irradiation caused the greatest decrease in cell viability. At 72 h, statistically significant decreases in cell viability were found with all concentrations of zoledronic acid with or without irradiation: 0 Gy (P < 0.001), 5 Gy (P < 0.001), 15 Gy (P < 0.001), and 30 Gy (P < 0.001). 50 μM and 100 μM doses of zoledronic acid combined with 5 Gy irradiation yielded the greatest decrease in cell migration capacity.

CONCLUSIONS

Zoledronic acid increases cytotoxic activity in the PE/CA-PJ15 cell line and reduces cell migration capacity. These findings suggest that combination therapy using biphosphates and radiation may offer a promising therapy.

The enhancement of radiosensitivity in human esophageal squamous cell carcinoma cells by zoledronic acid and its potential mechanism

Esophageal squamous cell carcinoma (ESCC) has a low 5-year patient survival rate. Radiotherapy, as a preoperative or postoperative treatment of surgery, has a crucial role in improving local control and survival of ESCC. Various chemotherapeutic and biologic agents have been used as radio-sensitizers in combination with radiotherapy. Here, we demonstrate that zoledronic acid (ZOL) has a radio-sensitizing effect on ESCC cells. Exposure of ESCC cancer cells to ZOL plus radiation resulted in increased cell death through arresting the cell cycle between S and G2/M phases. ZOL appeared to inhibit proliferation, tube formation and invasion of endothelial cells. These anti-angiogenetic effects were more marked concurrently with irradiation. In addition, synergistic suppressive effects on VEGF expression were observed after combined treatment. Our data suggest that the combination of ZOL and radiation is a promising therapeutic strategy to enhance radiation therapy for ESCC patients.

Zoledronic acid and radiation: toxicity, synergy or radiosensitization?

INTRODUCTION

Zoledronic acid (Z) is a bisphosphonate used in hypercalcaemia-related cancer, in complications for bone metastasis and in postmenopausal osteoporosis and it has been related to osteoradionecrosis, especially when associated with radiation to the head and neck structures.

OBJECTIVES

To determine the radiosensitization capacity of zoledronic acid in the combined treatment with ionizing radiation (IR) by evaluating its genotoxic and cytotoxic capacities in non-tumoral cells.

MATERIALS AND METHODS

The genotoxic effect of Z was studied by means of the micronucleus test in cytokinesis-blocked cells of human lymphocytes irradiated before and after a 2 Gy irradiation, while the cytotoxic effect was studied by a cell viability test in the PNT2 cell line before and after exposure to different X-ray doses (0-20 Gy) in four groups (Z alone, radiation alone, Z + IR and IR + Z).

RESULTS

A dose-dependent and time-dependent cytotoxic effect of Z and IR on PNT2 cells in vitro (p > 0.001) was demonstrated. With the concentrations recommended for humans, the combined treatment had a more pronounced effect than individual treatments (p < 0.001). The effect was synergic (CI < 1), increasing the Z enhancement ratio (2.6) and sensitization factor (56 %); the effect of Z was always greater after IR exposure. In the genotoxic effect, only the administration of Z after irradiation (IR + Z) increased chromosome damage (p < 0.001) and the sensibilization factor (35.7 %).

CONCLUSION

High concentrations of Z are toxic, but the concentrations recommended for clinical practice in humans give it the characteristics of a radiosensitization agent, whose effect is even greater when administered after IR.

Bisphosphonate treatment and radiotherapy in metastatic breast cancer

Patients with advanced breast cancer frequently develop metastasis to bone. Bone metastasis results in intractable pain and high risk of pathologic fractures due to osteolysis. The treatment of breast cancer patients with bone metastases requires a multidisciplinary approach. Radiotherapy is an established treatment for metastatic bone pain. It may be delivered either as a localized low dose treatment for localized bone pain or systemically for more widespread symptoms. Bisphosphonates have been shown to reduce morbidity and bone pain from bone metastases when given to patients with metastatic bone disease. In vivo studies indicate that early bisphosphonates administration in combination with radiotherapy improves remineralization and restabilization of osteolytic bone metastases in animal tumor models. This review focused on a brief discussion about biology of bone metastases, the effects of radiotherapy and bisphosphonate therapy, and possible mechanisms of combination therapy in metastatic breast cancer patients.

Targeting receptor tyrosine kinase signalling in small cell lung cancer (SCLC): what have we learned so far?

Small cell lung cancer (SCLC) is an aggressive form of lung cancer, which represents 13% of all cases and is strongly associated with cigarette smoking. The survival of SCLC patients is dismal and has not greatly improved in the last 20 years, despite advances in chemotherapy regimens and a better understanding of SCLC biology. The development of resistance to chemotherapy and metastasis are commonly recognized as important causes of poor clinical outcome in SCLC. Targeting receptor tyrosine kinase (RTK) signalling represents an attractive approach to develop new drugs for SCLC, in view of the accumulating data demonstrating that polypeptide growth factors play a key role in driving SCLC cell proliferation, chemoresistance and metastasis. The insulin-like growth factor-I receptor (IGF-IR), c-Kit, vascular endothelial growth factor receptor (VEGFR) and epidermal growth factor receptor (EGFR) have been identified as potential drug targets in SCLC. Moreover, downstream signalling mediators of RTKs, such as phosphoinositide 3-kinase (PI3K)/Akt and the mammalian target of rapamycin (mTOR) may also represent attractive candidate molecules for anti-cancer therapies in SCLC. Here we will review the available data concerning results with RTK inhibitors in SCLC and the clinical trials undertaken to investigate the potential of these compounds as anti-tumour agents in SCLC.