Protein Stability Regulation in Osteosarcoma: The Ubiquitin-like Modifications and Glycosylation as Mediators of Tumor Growth and as Targets for Therapy.

The identification of new therapeutic targets and the development of innovative therapeutic approaches are the most important challenges for osteosarcoma treatment. In fact, despite being relatively rare, recurrence and metastatic potential, particularly to the lungs, make osteosarcoma a deadly form of cancer. In fact, although current treatments, including surgery and chemotherapy, have improved survival rates, the disease's recurrence and metastasis are still unresolved complications. Insights for analyzing the still unclear molecular mechanisms of osteosarcoma development, and for finding new therapeutic targets, may arise from the study of post-translational protein modifications. Indeed, they can influence and alter protein structure, stability and function, and cellular interactions. Among all the post-translational modifications, ubiquitin-like modifications (ubiquitination, deubiquitination, SUMOylation, and NEDDylation), as well as glycosylation, are the most important for regulating protein stability, which is frequently altered in cancers including osteosarcoma. This review summarizes the relevance of ubiquitin-like modifications and glycosylation in osteosarcoma progression, providing an overview of protein stability regulation, as well as highlighting the molecular mediators of these processes in the context of osteosarcoma and their possible targeting for much-needed novel therapy.

Anti-proliferative, pro-apototic and anti-migratory properties of HDAC inhibitor PXD-101 on osteosarcoma cell lines.

The therapeutic strategies for osteosarcoma involve both surgical approach and chemotherapy, but the identification of new therapeutic targets is particularly necessary in patients with local chemo-resistance, recurrence and lung metastases. The role of epigenetic regulation in osteosarcoma is largely unknown. Thus, in this study we disclosed the effects of histone deacetylase inhibitor drug PXD-101 on human osteosarcoma (OS) cell lines with different aggressiveness, including Saos-2, HOS and 143B cell lines. XTT assays revealed that treatment of Saos-2, HOS and 143B cells with PXD-101 decreased cell viability in a concentration-dependent manner. Fluorescence-activated cell sorting (FACS) analysis showed that PXD-101 inhibited proliferation and induced cell apoptosis. Wound healing assay indicated that PXD-101 inhibited migration of osteosarcoma cells. Real-Time RT-qPCR and protein analysis highlighted reduced expression of Runx2, Osterix and Mad2, probably due to Cyclin B1 inhibition by PXD-101 treatment. To our knowledge, this is the first study that characterized the anti-tumoral effect of PXD-101 in OS cells, suggesting a potential new therapeutic approach in osteosarcoma patients.

Impairment in muscle strength and its determinants in primary hyperparathyroidism: A study in postmenopausal women.

Neuromuscular impairment is described among the non-classical complications of primary hyperparathyroidism (PHPT). However, the extent of this complications and related mechanisms have not been fully addressed. The study aimed at assessing muscle strength and its main determinants in postmenopausal women with PHPT. We studied 48 postmenopausal women with PHPT (mean age 60.8 ± 5.6 SD years; BMI 25.6 ± 5.5 kg/m2) and 38 healthy postmenopausal women (mean age 58.6 ± 5.9; BMI 25.2 ± 3.5). In all subjects, the maximum voluntary contraction (MVC, Newton, N) was measured by Hand held Dynamometer (Kayser Italia srl, Livorno, Italy) and the lumbar spine, total hip, femoral neck, and non dominant distal one-third radius areal BMD (aBMD) by dual X-ray absorptiometry (DXA) (Hologic, Waltham, MA). Serum ionized calcium (Ca++), parathyroid hormone (PTH), phosphorus (P), and 25-hydroxyvitaminD [25(OH)D] levels were measured in both groups. A subgroup of 30 PHPT women agreed to participate to the follow-up sub-study and were re-assessed 24 months after parathyroidectomy (n = 15) or after baseline evaluation (n = 15). Patients with PHPT had significant lower MVC values compared to healthy women (p < 0.001). As expected, serum Ca++ and PTH levels were higher and P lower in PHPT compared to controls. We observed a significant association between MVC and total hip and one-third radius aBMD (R = 0.320 and 0.370, p < 0.05) and negative association with Ca++ (R = -0.340, p < 0.05) in the PHPT group; MVC was positively associated with one-third radius aBMD (R = 0.360, p < 0.05) and negatively with age, BMI and myostatin (R = -0.390, -0.340 and -0.450, p < 0.05) in the group of healthy women. The linear model using BMI, Ca++, P, 25(OH)D, PTH, myostatin, and aBMD as covariates showed that one-third radius aBMD was positively associated with MVC in PHPT patients (p < 0.02) and in healthy subjects (p < 0.001). Additionally, serum PTH and myostatin were negatively associated with MVC in healthy subjects (p < 0.03 and p < 0.01). The linear model showed that surgery was associated with an increase in MVC (p < 0.05) in PHPT patients after 24 months, all other variables being equal and by controlling for baseline values of MVC. Handgrip strength is significantly impaired in postmenopausal women with PHPT. Some common mechanisms influencing muscle function exist in PHPT and in healthy subjects; they are associated with the reduced aBMD at cortical sites. Hypercalcemia seems to be one of the main determinants of impairment in muscle strength in PHPT, while no role is played by myostatin.