Zoledronic acid increases the antitumor effect of gefitinib treatment for non-small cell lung cancer with EGFR mutations

Bisphosphonate-Based Conjugates and Derivatives as Potential Therapeutic Agents in Osteoporosis, Bone Cancer and Metastatic Bone Cancer

Metastatic bone cancer occurs in every type of cancer but is prevalent in lung, breast, and prostate cancers. These metastases can cause extensive morbidity, including a range of skeletal-related events, often painful and linked with substantial hospital resource usage. The treatment used is a combination of chemotherapy and surgery. However, anticancer drugs are still limited due to severe side effects, drug resistance, poor blood supply, and non-specific drug uptake, necessitating high toxic doses. Bisphosphonates are the main class of drugs utilized to inhibit metastatic bone cancer. It is also used for the treatment of osteoporosis and other bone diseases. However, bisphosphonate also suffers from serious side effects. Thus, there is a serious need to develop bisphosphonate conjugates with promising therapeutic outcomes for treating metastatic bone cancer and osteoporosis. This review article focuses on the biological outcomes of designed bisphosphonate-based conjugates for the treatment of metastatic bone cancer and osteoporosis.

"The use of bisphosphonates to treat skeletal complications in solid tumours"

The skeleton is the most common site of secondary disease in breast cancer and prostate cancer, with up to 80% of patients with advanced disease developing bone metastases (BM). The proportion is also substantial in advanced lung cancer (20%-40%). Because of the high prevalence of cancers of the breast, prostate and lung, these cancers account for more than 80% of cases of metastatic bone disease occurring in solid tumours. Metastatic bone disease is associated with greatly increased bone resorption by osteoclasts, leading to moderate to severe pain and other skeletal complications, with major impact on quality of life (QoL). Skeletal Related Events (SREs) have been defined as: pathological long bone or vertebral fractures; spinal cord compression; need for radiation for pain relief or to prevent fracture/spinal cord compression, need for surgery to bone and hypercalcaemia. More recently, Symptomatic Skeletal Events (SSEs) have been defined to monitor QoL. Although there are currently no curative treatments for metastatic bone disease, patients with breast or prostate cancer and BM are now surviving for several years and sometimes longer, and prevention of SREs is the key aim to optimization of QoL. Since their discovery 50 years ago and their introduction more than 30 years ago into the field of metastatic bone disease, a range of oral and intravenous bisphosphonate drugs have made a major contribution to prevention of SREs. Large trials have clearly demonstrated the clinical value of different bisphosphonate-based drugs (including the oral drugs ibandronate and clodronate and intravenous agents such as zoledronate and pamidronate), in treatment of hypercalcaemia of malignancy and the reduction of SREs and SSEs in a range of cancers. Despite the success of denosumab in reducing osteolysis, bisphosphonates also remain mainstay drugs for treatment of metastatic bone disease. Recognizing the 50th Anniversary of the discovery of bisphosphonates, this review focuses on their continuing value in BM treatment and their future potential, for example in providing a bone-targeting vehicle for cytotoxic drugs.

Extra-skeletal effects of bisphosphonates

Bisphosphonates (BPs) are pyrophosphate analogues widely used in diseases related to bone loss and increased bone turnover. Their high affinity for bone hydroxyapatite makes them ideal agents for bone diseases, while preventing them from reaching other cells and tissues. Data of the last decade, however, have demonstrated extra-skeletal tissue deposition and a variety of non-skeletal effects have been recently recognized. As such, BPs have been shown to exert anti-tumor, immunomodulatory, anti-inflammatory and anti-diabetic effects. In addition, new delivery systems (liposomes, nanoparticles, hydrogels) are being developed in an effort to expand BPs clinical application to extra-skeletal tissues and enhance their overall therapeutic spectrum and effectiveness. In the present review, we outline current data on extra-skeletal actions of bisphosphonates and attempt to unravel the underlying pathophysiological mechanisms.

Targeting SREBP-2-Regulated Mevalonate Metabolism for Cancer Therapy

Recently, targeting metabolic reprogramming has emerged as a potential therapeutic approach for fighting cancer. Sterol regulatory element binding protein-2 (SREBP-2), a basic helix-loop-helix leucine zipper transcription factor, mainly regulates genes involved in cholesterol biosynthesis and homeostasis. SREBP-2 binds to the sterol regulatory elements (SREs) in the promoters of its target genes and activates the transcription of mevalonate pathway genes, such as HMG-CoA reductase (HMGCR), mevalonate kinase and other key enzymes. In this review, we first summarized the structure of SREBP-2 and its activation and regulation by multiple signaling pathways. We then found that SREBP-2 and its regulated enzymes, including HMGCR, FPPS, SQS, and DHCR4 from the mevalonate pathway, participate in the progression of various cancers, including prostate, breast, lung, and hepatocellular cancer, as potential targets. Importantly, preclinical and clinical research demonstrated that fatostatin, statins, and N-BPs targeting SREBP-2, HMGCR, and FPPS, respectively, alone or in combination with other drugs, have been used for the treatment of different cancers. This review summarizes new insights into the critical role of the SREBP-2-regulated mevalonate pathway for cancer and its potential for targeted cancer therapy.

Carbon-Ion Beam Irradiation Alone or in Combination with Zoledronic acid Effectively Kills Osteosarcoma Cells

Osteosarcoma (OSA) is the most common malignant bone tumor in children and adolescents. The overall five-year survival rate for all bone cancers is below 70%; however, when the cancer has spread beyond the bone, it is about 15–30%. Herein, we evaluated the effects of carbon-ion beam irradiation alone or in combination with zoledronic acid (ZOL) on OSA cells. Carbon-ion beam irradiation in combination with ZOL significantly inhibited OSA cell proliferation by arresting cell cycle progression and initiating KHOS and U2OS cell apoptosis, compared to treatments with carbon-ion beam irradiation, X-ray irradiation, and ZOL alone. Moreover, we observed that this combination greatly inhibited OSA cell motility and invasion, accompanied by the suppression of the Pi3K/Akt and MAPK signaling pathways, which are related to cell proliferation and survival, compared to individual treatments with carbon-ion beam or X-ray irradiation, or ZOL. Furthermore, ZOL treatment upregulated microRNA (miR)-29b expression; the combination with a miR-29b mimic further decreased OSA cell viability via activation of the caspase 3 pathway. Thus, ZOL-mediated enhancement of carbon-ion beam radiosensitivity may occur via miR-29b upregulation; co-treatment with the miR-29b mimic further decreased OSA cell survival. These findings suggest that the carbon-ion beam irradiation in combination with ZOL has high potential to increase OSA cell death.

Inhibitory effects of CP on the growth of human gastric adenocarcinoma BGC-823 tumours in nude mice

Objective

To investigate the potential antitumour effects of [2-(6-amino-purine-9-yl)-1-hydroxy-phosphine acyl ethyl] phosphonic acid (CP) against gastric adenocarcinoma.

Methods

Human BGC-823 xenotransplants were established in nude mice. Animals were randomly divided into control and CP groups, which were administered NaHCO₃ vehicle alone or CP dissolved in NaHCO₃ (200 µg/kg body weight) daily, respectively. Tumour volume was measured weekly for 6 weeks. Resected tumours were assayed for proliferative activity with anti-Ki-67 or anti-proliferating cell nuclear antigen (PCNA) antibodies. Cell apoptosis was examined using terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling (TUNEL) assays and with caspase-3 immunostaining. Proteins were measured by Western blotting.

Results

There was a significant reduction in tumour volume and a reduced percentage of Ki-67-positive or PCNA-positive cells in the CP group compared with the control group. The percentage of TUNEL-positive or caspase 3-positive cells significantly increased following CP treatment compared with the control group. Tumours from the CP group had higher levels of phosphorylated-extracellular signal-regulated kinase (p-ERK) and phosphorylated-AKT (p-AKT) compared with control tumours.

Conclusion

CP treatment inhibited tumour growth and induced tumour cell apoptosis in a nude mouse model of BGC-823 gastric adenocarcinoma. Activation of the AKT and ERK signalling pathways may mediate this antitumour activity.

Anti-angiogenic and anti-tumor effects of metronomic use of novel liposomal zoledronic acid depletes tumor-associated macrophages in triple negative breast cancer

Zoledronic acid (ZOL) has been used as an adjuvant therapy for breast cancer. It is suggested that ZOL might be associated with inhibition of macrophages, which in turn reduces tumor growth, metastasis and tumor angiogenesis. Moreover, metronomic therapy can inhibit tumor angiogenesis and tumor immune cells. Previously we developed ZOL based cationic liposomes that allowed a higher intratumor delivery of drug compared with free ZOL in vivo. Therefore, in this study, Asn-Gly-Arg (NGR) and PEG2000 were used as ligands to modify the surface of liposomes (NGR-PEG-LP-ZOL) in metronomic therapy to clear the tumor-associated macrophages (TAMs) and inhibit the formation of tumor angiogenesis, achieving the purpose of anti-tumor growth.

Our data showed that NGR-PEG-LP-ZOL metronomic therapy has the strongest inhibitory effect on tumor growth. Further, NGR-PEG-LP-ZOL metronomic therapy could significantly impair TAMs by inhibiting the expression of CD206 antibody in tumor tissues, decreasing the expression of cytokine related gene expression of TAMs, as well as reducing the percentage of TAMs in tumor tissues. In addition, NGR-PEG-LP-ZOL metronomic therapy could significantly inhibit the expression of tumor neovascular specific antibody CD31 and reduce the microvessel density. In conclusion, our study demonstrated that NGR-PEG-LP-ZOL metronomic therapy could impair TAMs by inhibiting tumor angiogenesis and enhance the antitumor effect of ZOL.