Role of denosumab in breast cancer

Design and synthesis of pyrimidinyl acyl thioureas as novel Hsp90 inhibitors in invasive ductal breast cancer and its bone metastasis

Invasive ductal carcinoma is the most common breast malignancies tumors and has tendency to bone metastases. Many oncogenic client proteins involved in formation of metastatic pathways. Stabilization, regulation, and maintenance of these oncogenic client proteins are provided with Heat Shock Protein 90 (Hsp90). Hsp90 perform these processes through its ATP binding and subsequent hydrolysis energy. Therefore, designing Hsp90 inhibitors is a novel cancer treatment method. However, many Hsp90 inhibitors have solubility problems and showed adverse effects in clinical trials. Thus, we designed and synthesized novel pyrimidinyl acyl thiourea derivatives to selectively inhibit Hsp90 alpha in human invasive ductal breast (MCF-7) and human bone osteosarcoma (Saos-2) cell lines. In vitro experiments showed that the compounds inhibited cell proliferation, ATP hydrolysis, and exhibited cytotoxic effect on these cancer cell lines. Further, gene expression was analyzed by microarray studies on MCF-7 cell lines. Several genes that play vital roles in breast cancer pathogenesis displayed altered gene expression in the presence of a selected pyrimidinyl acyl thiourea compound. Molecular docking studies were also performed to determine interaction between Hsp90 ATPase domain and pyrimidinyl acyl thiourea derivatives. The results indicated that the compounds are able to interact with Hsp90 ATP binding pocket and inhibit ATPase function. The designed compounds powerfully inhibit Hsp90 by an average of 1 μM inhibition constant. And further, the compounds perturb Hsp90 N terminal domain proper orientation and ATP may not provide required conformational change for Hsp90 function as evidenced by in silico experiments. Therefore, the designed compounds effectively inhibited both invasive ductal breast carcinoma and bone metastasis. Pyrimidinyl acyl thiourea derivatives may provide a drug template for effective treatment of invasive ductal breast carcinoma and its bone metastasis as well as new therapeutic perspective for drug design.

Denosumab for the treatment of bone metastases in breast cancer: evidence and opinion

INTRODUCTION

Denosumab, a fully human monoclonal antibody, targets the receptor activator of nuclear factor-kappaB (RANK) ligand, a protein essential for osteoclast differentiation, activity and survival. Loss of osteoclasts from the bone surface reduces bone turnover and bone loss in malignant and benign diseases. In breast cancer, bone metastases are frequently observed; cancer treatment-induced bone loss (CTIBL) may result as a consequence of endocrine treatment or chemotherapy. Furthermore, preclinical studies suggest a direct role of the RANK/RANK-ligand pathway in breast tumorigenesis. This paper reviews preclinical and clinical data on denosumab in breast cancer.

MATERIALS AND METHODS

Studies were identified through the Medline database. Key search terms included: AMG-162, bisphosphonates, denosumab, RANK-ligand and zoledronic acid. Information available in abstract form only was retrieved from major oncology meetings, such as the American Society of Clinical Oncology (ASCO) annual meeting, ASCO breast meeting, European Cancer Organization, European Society of Medical Oncology and the San Antonio Breast Cancer Symposium.

RESULTS

Denosumab was consistently well tolerated throughout clinical trials, although the observed incidence of osteonecrosis of the jaw was comparable to that with bisphosphonates. Efficacy as determined by a reduction of skeletal-related events was at least equal to zoledronic acid, and superior in one phase III study conducted in patients with metastatic breast cancer. Clinical trials investigating the role of denosumab for the prevention of CTIBL and breast cancer recurrences are currently ongoing.

CONCLUSION

In conclusion, denosumab appears to be an effective and safe treatment option in patients with bone metastases from breast cancer with the potential of also preventing CTIBL.

Steps in prostate cancer progression that lead to bone metastasis

Prostate cancer is a complex disease in which metastasis to the bone is the main cause of death. Initial stages of metastasis are generally similar to those for most solid tumors; however, the mechanisms that underlie the homing of prostate tumor cells to the bone are not completely understood. Prostate cancer bone metastasis is also a microenvironment-driven disease, involving bidirectional interactions between the tumor and the bone microenvironment. In this review, we discuss the current understanding of the biologic processes and regulatory factors involved in the metastasis of prostate cancer cells, and their specific properties that promote growth in bone. Although many of these processes still need to be fully elucidated, a better understanding of the complex tumor/microenvironment interplay is slowly leading to more effective therapies for patients with prostate cancer bone metastases.

Past, present and future of therapies in pediatric sarcomas

Limited progress has been made over the past 30 years in improving the outcome of patients with high-risk pediatric sarcomas. The 5-year overall survival rate remains at 20% or less with metastatic sarcomas. Therefore, current and future research is focused on the identification and development of molecular or biological agents targeting the pathogenic pathways in sarcomas, either alone or in combination with conventional chemotherapy. To this end, the most promising activity has been seen with IGF-1 receptor antibodies and mTOR inhibitors. Other agents of interest are oncolytic viruses, epigenetic modulators (e.g., histone deacetylase inhibitors), immune modulators (e.g., muramyl tripeptide phosphatidylethanolamine) and other biological agents (e.g., trabectedin). In addition to the development of novel drugs, the other major area of recent focus is developing immune therapies, such as dendritic cell vaccines and adoptive immunotherapy for treating pediatric sarcomas. This article discusses the successes, the failures and the future direction of these therapies.

Osteosarcoma

It has been difficult to identify the molecular features central to the pathogenesis of osteosarcoma owing to a lack of understanding of the cell or origin, the absence of identifiable precursor lesions, and its marked genetic complexity at the time of presentation. Interestingly, several human genetic disorders and familial cancer syndromes, such as Li-Fraumeni syndrome, are linked to an increased risk of osteosarcoma. Association of these same genetic alterations and osteosarcoma risk have been confirmed in murine models. Osteosarcoma is associated with a variety of genetic abnormalities that are among the most commonly observed in human cancer; it remains unclear, however, what events initiate and are necessary to form osteosarcoma. The availability of new resources for studying osteosarcoma and newer research methodologies offer an opportunity and promise to answer these currently unanswered questions. Even in the absence of a more fundamental understanding of osteosarcoma, association studies and preclinical drug testing may yield clinically relevant information.

Two distinct mechanisms underlie progesterone-induced proliferation in the mammary gland

The mouse mammary gland develops postnatally under the control of female reproductive hormones. Estrogens and progesterone trigger morphogenesis by poorly understood mechanisms acting on a subset of mammary epithelial cells (MECs) that express their cognate receptors, estrogen receptor alpha (ERalpha) and progesterone receptor (PR). Here, we show that in the adult female, progesterone drives proliferation of MECs in two waves. The first, small wave, encompasses PR(+) cells and requires cyclin D1, the second, large wave, comprises mostly PR(-) cells and relies on the tumor necrosis factor (TNF) family member, receptor activator of NF-kappaB-ligand (RANKL). RANKL elicits proliferation by a paracrine mechanism. Ablation of RANKL in the mammary epithelium blocks progesterone-induced morphogenesis, and ectopic expression of RANKL in MECs completely rescues the PR(-/-) phenotype. Systemic administration of RANKL triggers proliferation in the absence of PR signaling, and injection of a RANK signaling inhibitor interferes with progesterone-induced proliferation. Thus, progesterone elicits proliferation by a cell-intrinsic and a, more important, paracrine mechanism.