Citations

The objective of this study was to identify signaling pathways leading to the development of interstitial fibrosis and tubular atrophy in the stenotic kidney and compensatory hypertrophy/hyperplasia of the contralateral kidney in a murine 2 kidney 1 clip model of hypertensive nephrosclerosis. Mice were studied 2, 5, and 11 weeks after undergoing surgery to establish unilateral renal artery stenosis (RAS). RAS animals, but not sham controls, became hypertensive within 1 week. Compensatory enlargement of the contralateral kidney was associated with a transient increase in proliferation (as assessed by PCNA and Mib‐1), p‐ERK, caspase 3, p27, p53, and TGF‐β expression at early time points, with return to baseline levels by 11 weeks. Tubular atrophy in the stenotic kidney was associated with a persistent increase in p‐ERK, Mib‐1, p53, p21, and p27 expression through 11 weeks. Proliferative activity was observed in tubular epithelial cells and in inflammatory cells. The atrophic kidneys had little apoptotic activity (caspase 3, TUNEL staining). The atrophic kidneys showed progressive increases in TGF‐β and α‐SMA expression and extracellular matrix deposition throughout 11 weeks. Interstitial inflammation was associated with increased MCP‐1 expression. Mechanisms underlying this differential response to unilateral RAS await definition.

Many diseases are caused by altered epithelial Cl − or HCO 3 − transport. Mutations in the SLC26A3 transporter are causative for congenital chloride‐losing diarrhea; however, no other SLC26 transporter plays such a direct genetic role in disorders of epithelial Cl − transport. SLC26A9 is expressed in the lung, stomach, intestine and kidney (lesser extent) but its physiological function in these epithelia is not clear. Thus far, no diseases result from SLC26A9 mutations. However, database analysis reveals three single nucleotide polymorphisms (SNPs). We reasoned that the human SLC26A9‐SNPs would provide insight into what a disease phenotype might be functionally manifest. Here we analyzed the ion transport characteristics of human SLC26A9 and its SNPs: V622L, V744M and H748R. Human SLC26A9 and its three SNPs were expressed in Xenopus laevis oocytes. Effects on ion transport were evaluated using ion selective electrodes and voltage clamping. Measuring Cl − and HCO 3 − flux, our results show that SLC26A9 is a Cl − /HCO 3 − exchanger. One SNP, V622L, is located in the C‐terminus just before the STAS domain of SLC26A9. V622L has ~50% function (current and Cl − transport). These results suggest that the possession of V622L allele in humans would decrease SLC26A9 function and modulate the risk for lung disease (cystic fibrosis), gut disease (gastric ulcer) or hypertension, due to reduced Cl − transport across epithelial cells.

Frataxin is a conserved mitochondrial protein whose deficiency causes mitochondrial iron imbalance, energy deficit, and oxidative stress, leading to the progressive neurologic and cardiac disease Friedreich ataxia. We reported previously that the mature form of human frataxin is degraded to shorter products by an unknown protease, designated frataxin degrading peptidase (FDP). We hypothesized that FDP might represent a new mechanism to modulate mitochondrial iron balance via regulation of frataxin turnover. We have now purified FDP from different tissue sources. Interestingly, the enzyme corresponds to a known mitochondrial homodimeric oxidoreductase involved in energy metabolism and antioxidant defense. The presence of proteolytic activity has been confirmed with a recombinant form of the oxidoreductase produced in E. coli . The 3D structure of the enzyme suggests the presence of a Ser‐His‐Glu catalytic triad at the homodimer interface. Indeed, the proteolytic activity is stimulated by point mutations or other conditions that destabilize the homodimer, and is inactivated by certain serine protease inhibitors. Combining oxidoreductase and proteolytic functions in the same protein may be a mechanism to integrate changes in energy metabolism and redox status with mitochondrial iron balance. [Supported by the Muscular Dystrophy Association and a pre‐doctoral fellowship from the American Heart Association (0415379Z)].

We have previously demonstrated that, in vitro, c‐AMP specific PDE3 inhibitors block mitogenesis of mesangial cells (Am J Physiol Renal Physiol, 2004) and PDE4 inhibitors block cytokine stimulated MCP‐1 expression (Am J Physiol Cell Physiol, 2005). The in vivo relevance of these findings has not been previously established. Mice were treated with the nonselective cAMP PDE inhibitor pentoxifylline (PTX) prior to bilateral clamping of the renal arteries for 30 minutes, followed by reperfusion for 1 and 4 days. PTX blunted the increase in BUN and creatinine after 1 day (−38% and −43%, respectively, p<0.05), and after 4 days (−80% and −44%, respectively, p<0.05). PTX reduced the extent of tubular necrosis (1 day: 39.13% vs. 52.5%; 4 days: 2.5% vs. 23.33%, p<0.05, p=NS. % cortical area in PTX vs. IR). PTX reduced PCNA expression 4 days after IR, as assessed by Western blot (−43%, p<0.05), and reduced caspase 3 activity one day after IR (−43%, p<0.05). PTX markedly reduced expression of MMP10 and Cox‐2 one day after IR (26 and 4 folds, respectively, p<0.05), which are induced in response to acute inflammation. PTX significantly reduced cyclin F, cyclin A2 and Ki67 expression 4 days after IR (124, 7 and 9 folds, respectively, p<0.05), which are induced in response to proliferation. We conclude that PTX ameliorates IR injury through c‐AMP mediated reduction in proliferative and inflammatory responses to acute injury.

The SLC26A9 protein mediates Cl‐ transport as a Cl‐ channel and a Cl‐/HCO3 exchanger in the several epithelial cells, e.g., gut, lung, kidney. Topology analysis from BicA, a member of the SulP/SLC26A family, suggests that Slc26 proteins consists of 12 predicted transmembrane regions. However, the topology model of human SLC26 transporters has not yet been directly investigated. In this study, 12 HA‐inserted SLC26A9 mutants were constructed and expressed in Xenopus oocytes. Chemiluminescence was used to determine which HA‐tags were accessible from the extracellular surface. 157‐160 and 352‐353 sites of human SLC26A9 were identified as extracellular sites. Interestingly, the SLC26A9 HA (159‐160) mutant has ~40% Cl‐ transport activity, but this decreased function could be rescued by coexpression with another low function cSNP (T127N‐SLC26A9). These results revealed that the topology of TM region of SLC26A9 may different from that of BicA and also indicate that human SLC26A9 functions as dimer. Grant Funding Source : Supported by NIH EY 017732 (MFR)

Abstract Immune checkpoint blockade (ICB) has revolutionized cancer therapy. However, the response of patients to ICB is difficult to predict. Here, we examined 81 patients with lung cancer under ICB treatment and found that patients with MET amplification were resistant to ICB and had a poor progression-free survival. Tumors with MET amplifications had significantly decreased STING levels and antitumor T-cell infiltration. Furthermore, we performed deep single-cell RNA sequencing on more than 20,000 single immune cells and identified an immunosuppressive signature with increased subsets of XIST- and CD96-positive exhausted natural killer (NK) cells and decreased CD8+ T-cell and NK-cell populations in patients with MET amplification. Mechanistically, we found that oncogenic MET signaling induces phosphorylation of UPF1 and downregulates tumor cell STING expression via modulation of the 3′-UTR length of STING by UPF1. Decreased efficiency of ICB by MET amplification can be overcome by inhibiting MET. Significance: We suggest that the combination of MET inhibitor together with ICB will overcome ICB resistance induced by MET amplification. Our report reveals much-needed information that will benefit the treatment of patients with primary MET amplification or EGFR–tyrosine kinase inhibitor resistant-related MET amplification. This article is highlighted in the In This Issue feature, p. 2659

ObjectiveTo use probe oscillation shear wave elastography (PROSE) with two vibration sources to generate two shear waves in the imaging plane to quantitatively assess the shear wave speeds (SWSs) of muscles with and without the diagnosis of taut bands (TB) and/or myofascial trigger points (MTrPs).MethodsThirty‐three patients were scanned with the PROSE technique. Shear waves were generated through continuous vibration of the ultrasound probe, while the shear wave motions were detected using the same probe. SWSs for the sides with and without TBs and/or MTrPs were computed and compared. The pressure pain thresholds (PPTs) were measured as an indicator of maximum pain tolerance of patients. The statistical differences between the SWSs with and without TBs and/or MTrPs with different PPT values were analyzed using the nonparametric Wilcoxon rank‐sum test.ResultsThe mean SWSs for the sides with TBs and/or MTrPs are faster than that of the contralateral side without TBs and/or MTrPs. A significant difference was observed between mean SWSs with and without TBs and/or MTrPs without any information of PPT, with rank‐sum test P < .005. Additionally, with the information of PPT, a significant difference was observed between mean SWSs for the sides with and without TBs and/or MTrPs, for PPT values between 0 and 50 N/cm2 (P < .005), but for PPT values between 50 and 90 N/cm2, it was difficult to differentiate mean SWSs with and without TBs and/or MTrPs.ConclusionOur preliminary results show that SWSs measured from patients had a significant difference between the mean SWSs with and without TBs and/or MTrPs.

11536 Background: Ripretinib is a switch-control tyrosine kinase inhibitor that broadly inhibits KIT and PDGFRA kinase signaling. In the INVICTUS study (NCT03353753), patients with advanced GIST (≥4th-line) receiving ripretinib had a median progression-free survival (mPFS) of 6.3 months vs 1.0 month for patients receiving placebo (HR = 0.15, p <0.0001). In an earlier phase 1 dose escalation study, the maximum tolerated dose was not reached with doses up to 200 mg twice daily (BID). Here, we report efficacy, safety, and pharmacokinetic data for IPDE patients initially randomized to ripretinib from the phase 3 INVICTUS study based on data as of 10 Aug 2020. Methods: A total of 129 patients were randomized 2:1 to ripretinib 150 mg once daily (QD; n = 85) or placebo (n = 44). Patients receiving ripretinib 150 mg QD who had progressive disease (PD) as assessed by blinded independent central review (BICR) using mRECIST were given the option for IPDE to 150 mg BID. Tumor response assessments were performed every 28 days for 4 cycles and every 56 days thereafter (including after IPDE). The primary endpoint was PFS. For this exploratory analysis, PFS1 for IPDE patients was defined as the time from randomization to PD; PFS2 for IPDE patients was the time from the first dose of ripretinib 150 mg BID to PD or death. PFS1 and PFS2 were based on BICR. Results: Of 85 patients treated with ripretinib 150 mg QD, 43 patients with BICR PD dose escalated to 150 mg BID. Baseline characteristics of IPDE patients at time of study entry were similar to those observed in the original ripretinib QD arm and similar to the 22 patients with BICR PD who either remained on 150 mg QD or discontinued treatment. IPDE patients had a mPFS1 of 4.6 months (95% CI, 2.7–6.4) and a mPFS2 of 3.7 months (95% CI, 3.1–5.3); mPFS2/mPFS1=80%. The IPDE dosing period was well tolerated without the emergence of new safety concerns. The most common new or worsening (unchanged or improving grades not included) treatment-emergent adverse event (TEAE) for IPDE patients during the BID period was abdominal pain (30.2% all grades and 7% Grade 3–4 vs 41.9% and 4.7% in QD period, respectively). The most common Grade 3–4 TEAE in the BID period was anemia (14% vs 2.3% in QD period). IPDE from QD to BID resulted in an approximately 2-fold increase in the steady state trough concentration. Conclusions: Similar to the phase 1 study wherein IPDE to 150 mg BID following PD provided clinical benefit with a mPFS1 of 5.5 months and mPFS2 of 4.6 months (mPFS2/mPFS1=84%) for patients with ≥4th-line GIST, these analyses from INVICTUS indicate that IPDE to ripretinib 150 mg BID can also provide additional meaningful clinical benefit and a similar tolerability profile to the 150 mg QD regimen for patients with ≥4th-line GIST that progressed following treatment with ripretinib 150 mg QD. Clinical trial information: NCT03353753.

8569 Background: Immune checkpoint inhibitor (atezolizumab or durvalumab) combined with platinum-etoposide is the standard first-line therapy for patients with extensive-stage small cell lung cancer (ES-SCLC). The phase III clinical trials that led to the approval of chemoimmunotherapy in ES-SCLC, excluded patients with an Eastern Cooperative Group (ECOG) Performance Status (PS) of Two or Greater. Therefore, data on efficacy of this combination in this subgroup of ES-SCLC patients whose performance status two or greater is limited. Methods: A retrospective analysis was performed of patients diagnosed with ES-SCLC who received chemoimmunotherapy (atezolizumab or durvalumab) within the Mayo Clinic Health System between January 2016 and January 2021. Cases were identified from clinical databases at Mayo Clinic. Data on demographics, ECOG-PS, date of diagnosis, date of progression, whole brain radiation, CNS involvement, liver involvement, stereotactic body radiation, chest consolidation, platinum sensitivity, lines of therapy and last follow up date were extracted. Overall Survival (OS) and progression free survival (PFS) for ECOG-PS 2-3 were compared to patients with an ECOG-PS 0-1. Results: A total of 84 patients were identified with a median age of 68.2 (48-88) years old. Of these, 54 patients were identified with an ECOG-PS 0-1 and 30 patients with an ECOG-PS 2-3. The median PFS for the ECOG PS 0-1 cohort was 5.2 months (95% CI 4.6-6.1) while the median PFS for the ECOG-PS 2-3 cohort was 6.0 months (95% CI 4.2-7.7; logrank p = 0.93). The median OS for the ECOG-PS 0-1 cohort was 10.8 months (95% CI 8.5-12.9) while the median OS for the ECOG-PS 2-3 cohort was 10.3 months (95% CI 6.0-14.1; logrank p = 0.39). Hazard ratios of ECOG-PS 0-1 versus 2-3 showed no tendency of increased PFS or OS for either group within cox proportional hazards models. Forty-three percent of ECOG-PS 0-1 achieved a partial response (PR) and 57% of patients who had ECOG-PS 2-3 also achieved a PR (Fisher’s exact p = 0.23). A complete response was found in 4% of ECOG-PS 0-1 compared to 3% in the ECOG-PS 2-3 cohort. For patients who responded to initial therapy, 46% of ECOG-PS 2-3 patients had a platinum sensitive relapse while only 33% of ECOG-PS 0-1 were still platinum sensitive at the time of relapse. Five ECOG-PS 2-3 patients were able to receive a second-line therapy. Conclusions: To our knowledge, this is the first study to evaluate chemoimmunotherapy in the subgroup of ES-SCLC patients with an ECOG-PS 2 or greater. This retrospective study demonstrated no significant difference in PFS, OS, and ability to achieve a least a PR in ECOG-PS 2-3 cohort when compared to ECOG-PS 0-1. Therefore, chemoimmunotherapy should not be reserved for only an ECOG-PS of 0-1 but should be considered for all treatment eligible patients.

A de novo missense variant in Rag GTPase protein C (RagCS75Y) was recently identified in a syndromic dilated cardiomyopathy (DCM) patient. However, its pathogenicity and the related therapeutic strategy remain unclear. We generated a zebrafish RragcS56Y (corresponding to human RagCS75Y) knock-in (KI) line via TALEN technology. The KI fish manifested cardiomyopathy-like phenotypes and poor survival. Overexpression of RagCS75Y via adenovirus infection also led to increased cell size and fetal gene reprogramming in neonatal rat ventricle cardiomyocytes (NRVCMs), indicating a conserved mechanism. Further characterization identified aberrant mammalian target of rapamycin complex 1 (mTORC1) and transcription factor EB (TFEB) signaling, as well as metabolic abnormalities including dysregulated autophagy. However, mTOR inhibition failed to ameliorate cardiac phenotypes in the RagCS75Y cardiomyopathy models, concomitant with a failure to promote TFEB nuclear translocation. This observation was at least partially explained by increased and mTOR-independent physical interaction between RagCS75Y and TFEB in the cytosol. Importantly, TFEB overexpression resulted in more nuclear TFEB and rescued cardiomyopathy phenotypes. These findings suggest that S75Y is a pathogenic gain-of-function mutation in RagC that leads to cardiomyopathy. A primary pathological step of RagCS75Y cardiomyopathy is defective mTOR–TFEB signaling, which can be corrected by TFEB overexpression, but not mTOR inhibition.