Novel bone-targeted parathyroid hormone-related peptide antagonists inhibit breast cancer bone metastases

Context-Dependent Estrogenic Actions of (+)-Pisatin Produced in Elicited Green or Snow Pea (Pisum sativum)

Legumes are a predominant source of isoflavones, termed phytoestrogens, that mimic 17β-estradiol (E2). Phytoalexins are inducible isoflavones produced in plants subjected to environmental stressors (e.g., UV, heat, or fungi). This study investigated estrogenic activity of snow and green peas elicited with Aspergillus sojae. Elicited extracts increased estrogenic activity and proliferation of breast cancer cells (MCF-7 or T47D) in a dose-dependent manner but exhibited antiestrogenic activity when combined with synthetic E2. HPLC analysis of elicited pea extracts identified (+)-pisatin as the primary phytoalexin, which was produced significantly (p < 0.0001) more in snow pea compared to green pea. RNA sequencing results suggested potential functional effects on endothelial cells and tissue vascularization. Indeed, (+)-pisatin enhanced metrics of network assembly and maturation in a microphysiological model of bulk tissue vasculogenesis. Thus, context-dependent functional effects of (+)-pisatin and pharmacologically similar phytoestrogens on the entire tissue microenvironment should be considered in preclinical investigation as potential therapeutic agents.

A parathyroid hormone/salt-inducible kinase signaling axis controls renal vitamin D activation and organismal calcium homeostasis

The renal actions of parathyroid hormone (PTH) promote 1,25-vitamin D generation; however, the signaling mechanisms that control PTH-dependent vitamin D activation remain unknown. Here, we demonstrated that salt-inducible kinases (SIKs) orchestrated renal 1,25-vitamin D production downstream of PTH signaling. PTH inhibited SIK cellular activity by cAMP-dependent PKA phosphorylation. Whole-tissue and single-cell transcriptomics demonstrated that both PTH and pharmacologic SIK inhibitors regulated a vitamin D gene module in the proximal tubule. SIK inhibitors increased 1,25-vitamin D production and renal Cyp27b1 mRNA expression in mice and in human embryonic stem cell-derived kidney organoids. Global- and kidney-specific Sik2/Sik3 mutant mice showed Cyp27b1 upregulation, elevated serum 1,25-vitamin D, and PTH-independent hypercalcemia. The SIK substrate CRTC2 showed PTH and SIK inhibitor-inducible binding to key Cyp27b1 regulatory enhancers in the kidney, which were also required for SIK inhibitors to increase Cyp27b1 in vivo. Finally, in a podocyte injury model of chronic kidney disease-mineral bone disorder (CKD-MBD), SIK inhibitor treatment stimulated renal Cyp27b1 expression and 1,25-vitamin D production. Together, these results demonstrated a PTH/SIK/CRTC signaling axis in the kidney that controls Cyp27b1 expression and 1,25-vitamin D synthesis. These findings indicate that SIK inhibitors might be helpful for stimulation of 1,25-vitamin D production in CKD-MBD.

Treatment of Hypercalcemia of Malignancy

The treatment of hypercalcemia of malignancy (HCM) consists of enhancing renal calcium excretion, mostly through hydration with isotonic fluids and the use of antiresorptive therapies. Intravenous zoledronic acid is currently the first-line treatment. Subcutaneous denosumab is used for bisphosphonate-refractory hypercalcemia and in patients with renal failure. There is no evidence that bisphosphonates prevent the occurrence of HCM. Conversely, denosumab, compared with zoledronic acid, is associated with a lower risk of HCM, both first episode and recurrence, in patients with breast cancer and multiple myeloma.

Hypercalcemia of Malignancy

Hypercalcemia of malignancy (HCM) is considered an oncologic emergency associated with significant symptom burden and increased comorbid conditions and mortality. Underlying pathologic processes most often stimulate osteoclast-mediated bone resorption. Although long-term control of HCM depends on effective management of the underlying cancer, temporizing management strategies for acute and/or symptomatic HCM include hydration and antiresorptive bone-modifying agents. Although most patients respond well to the antiresorptive therapies available, further investigation into other agents for those who are refractory to both bisphosphonates and denosumab is needed.