Stimulating the Gq-coupled P2Y ₂ receptor ( P2ry2 ) lowers blood pressure. Global knockout of P2ry2 increases blood pressure. Vascular and renal mechanisms are believed to participate in P2ry2 effects on blood pressure. To isolate the role of the kidneys in P2ry2 effects on blood pressure and to reveal the molecular and cellular mechanisms of this action, we test here the necessity of the P2ry2 and the sufficiency of Gq-dependent signaling in renal principal cells to the regulation of the epithelial Na ⁺ channel (ENaC), sodium excretion, and blood pressure. Activating P2ry2 in littermate controls but not principal cell–specific P2ry2 -knockout mice decreased the activity of ENaC in renal tubules. Moreover, deletion of P2ry2 in principal cells abolished increases in sodium excretion in response to stimulation of P2ry2 and compromised the normal ability to excrete a sodium load. Consequently, principal cell–specific knockout of P2ry2 prevented decreases in blood pressure in response to P2ry2 stimulation in the deoxycorticosterone acetate–salt (DOCA-salt) model of hypertension. In wild-type littermate controls, such stimulation decreased blood pressure in this model of hypertension by promoting a natriuresis. Pharmacogenetic activation of Gq exclusively in principal cells using targeted expression of Gq–designer receptors exclusively activated by designer drugs and clozapine N -oxide decreased the activity of ENaC in renal tubules, promoting a natriuresis that lowered elevated blood pressure in the DOCA-salt model of hypertension. These findings demonstrate that the kidneys play a major role in decreasing blood pressure in response to P2ry2 activation and that inhibition of ENaC activity in response to P2ry2 -mediated Gq signaling lowered blood pressure by increasing renal sodium excretion.

Cisplatin (CDDP) is an important anticancer drug. A common side effect of CDDP is renal salt and water-wasting syndrome (RSWS). The origin of RSWS is obscure. Emerging evidence, though, suggests that broad inhibition of sodium transport proteins by CDDP may result in decreases in tubular reabsorption, causing increases in sodium and water excretion. In this sense, CDDP would be acting like a diuretic. The effect of CDDP on the epithelial Na⁺ channel (ENaC), which is the final arbiter fine-tuning renal Na⁺ excretion, is unknown. We test here whether CDDP affects ENaC to promote renal salt and water excretion. The effects of CDDP and benzamil (BZM), a blocker of ENaC, on excretion of a sodium load were quantified. Similar to BZM, CDDP facilitated renal Na⁺ excretion. To directly quantify the effects on ENaC, principal cells in split-open tubules were patch clamped. CDDP, at doses comparable to those used for chemotherapy (1.5 µM), significantly decreased ENaC activity in native tubules. To further elaborate on this mechanism, the dose-dependent effects of CDDP on mouse ENaC (mENaC) heterologously expressed in Chinese Hamster Ovary (CHO) cells were tested using patch clamping. As in native tubules, CDDP significantly decreased the activity of mENaC expressed in CHO cells. Dose–response curves and competition with amiloride identified CDDP as a weak inhibitor of ENaC (apparent IC₅₀ = 1 µM) that competes with amiloride for inhibition of the channel, weakening the inhibitory actions of the latter. Such observations are consistent with CDDP being a partial modulator of ENaC, which possibly has a binding site that overlaps with that of amiloride. These findings are consistent with inhibition of ENaC by CDDP contributing to the RSWS caused by this important chemotherapy drug.

Malignant rhabdoid tumors (MRTs) are among the most aggressive and treatment-resistant malignancies affecting infants, originating in the kidney, brain, liver, and soft tissues. The 5-year event-free survival rate for these cancers is a mere 20%. In nearly all cases of MRT, the SMARCB1 gene (occasionally SMARCA4)—a pivotal component of the SWI/SNF chromatin remodeling complex—is homozygously deleted, although the precise etiology of these tumors remains unknown. While young patients with localized MRT generally show improved outcomes, especially those who are older and have early-stage disease, the overall prognosis remains poor despite optimal standard treatments. This highlights the urgent need for more effective treatment strategies. We investigated the antitumor activity of a PARP1 inhibitor (talazoparib, TLZ) combined with a DNA alkylating agent (temozolomide, TMZ) in MRT xenograft models. PARP1 is a widely targeted molecule in cancer treatment and, beyond its role in DNA repair, it participates in transcriptional regulation by recruiting chromatin remodeling complexes to modulate DNA accessibility for RNA polymerases. To widen the therapeutic window of the drug combination, we employed PEGylated TLZ (PEG~TLZ), which has been reported to reduce systemic toxicity through slow drug release. Remarkably, our findings indicate that five out of six MRT xenografts exhibited an objective response to PEG~TLZ+TMZ therapy. Significantly, the loss of SMARCB1 was found to confer a protective effect, correlating with higher expression levels of DNA damage and repair proteins in SMARCB1-deficient MRT cells. Additionally, we identified MGMT as a potential biomarker indicative of in vivo MRT response to PEG~TLZ+TMZ therapy. Moreover, our analysis revealed alterations in signaling pathways associated with the observed antitumor efficacy. This study presents a novel and efficacious therapeutic approach for MRT, along with a promising candidate biomarker for predicting tumor response.

Purpose: Vobramitamab duocarmazine (vobra duo) is a duocarmycin-based, humanized antibody–drug conjugate (ADC) targeting B7-H3, with a drug-to-antibody ratio of ∼2.7. Vobra duo has demonstrated robust antitumor activity in multiple adult cancer models, along with favorable pharmacokinetic and safety profiles in cynomolgus monkeys. Early results from phase I/II clinical trials (NCT03729596) have shown manageable toxicity and promising objective responses in patients with metastatic castration-resistant prostate cancer. Given the high expression of B7-H3 in pediatric solid tumors, this target is emerging as a compelling therapeutic opportunity in pediatric oncology. Experimental Design: Antitumor activity of vobra duo was evaluated in pediatric solid tumor xenograft models, including Ewing sarcoma, rhabdomyosarcoma, neuroblastoma, osteosarcoma, malignant rhabdoid tumor, hepatoblastoma, and Wilms tumor. Tumor-bearing mice received a single intraperitoneal dose of vobra duo (6 mg/kg) or a matched control ADC (SYD988, anti-CD20 ADC with an identical linker and payload). Tumor progression was defined as a fourfold increase in tumor volume. Event-free survival was analyzed using Kaplan–Meier methods, and objective responses were categorized as partial, complete, or maintained complete response. Results: Vobra duo induced objective responses across multiple tumor types, whereas the control ADC showed limited activity. No clear association was observed between B7-H3 protein expression and therapeutic response. Conclusions: These findings demonstrate the broad preclinical efficacy of vobra duo in pediatric solid tumors and support further clinical investigation of B7-H3–targeted therapies in children.

Plots of event-free-survival (EFS) and relative tumor volume (RTV) changes over time for osteosarcoma models. Treatment groups: A = control, B = vobra duo: 6 mg/kg, IP, Day 0 × 1, C=SYD988: 6 mg/kg, IP, Day 0 × 1. Bold lines on RTV plots represent group median tumor volume changes.

CD276 gene expression from pedcBioportal public databases (to support Figure 4B).