Citations

Abstract Leucine-rich repeat kinase 2 (LRRK2) phosphorylates a subset of Rab GTPases that regulate receptor trafficking; activating mutations in LRRK2 are linked to Parkinson’s disease. Rab phosphorylation is a transient event that can be reversed by phosphatases, including PPM1H, that acts on phosphoRab8A and phosphoRab10. Here we report a phosphatome-wide siRNA screen that identified PPM1M as a phosphoRab12-preferring phosphatase that also acts on phosphoRab8A and phosphoRab10. Upon knockout from cells or mice, PPM1M displays selectivity for phosphoRab12. As shown previously for mice harboring LRRK2 pathway mutations, knockout of Ppm1m leads to primary cilia loss in striatal cholinergic interneurons. We have also identified a rare PPM1M mutation in patients with Parkinson’s disease that is catalytically inactive when tested in vitro and in cells. These findings identify PPM1M as a key player in the LRRK2 signaling pathway and provide a new therapeutic target for the possible benefit of patients with Parkinson’s disease. Teaser Parkinson’s linked Rab phosphorylation is reversed by PPM1M; the inactive D440N variant is implicated in rare patient cases.

ImportanceImmune checkpoint inhibitors (ICIs) have been approved for treatment of microsatellite instable (MSI-H) metastatic colorectal cancer (mCRC), but factors associated with receipt and efficacy of ICIs in routine clinical practice remain largely unknown.ObjectiveTo identify factors associated with receipt of ICIs and associated survival outcomes among patients with mCRC in routine clinical practice.Design, Setting, and ParticipantsThis population-based cohort study used deidentified data from a nationwide electronic health record–derived database to include 18 932 patients diagnosed with mCRC between January 2013 and June 2019. Population-based patients were diagnosed with de novo mCRC and had at least 2 documented clinical visits on or after the date of diagnosis. The study analyses were performed between September 2020 and April 2021.ExposurePatients received ICI therapy and/or chemotherapy as part of a systemic treatment for mCRC.Main Outcomes and MeasuresThe outcomes were receipt of ICI therapy, overall survival (OS), and time to treatment discontinuation (TTD).ResultsIn this cohort study of 18 932 patients diagnosed with mCRC (10 537 [55.7%] male; 546 [2.9%] Asian, 2005 [10.6%] Black or African American, 1674 [8.8%] Hispanic, 12 338 [65.2%] White, 4043 [21.4%] unknown race or ethnicity; median [IQR] age at metastatic diagnosis, 64.6 [55.0-73.3] years), patients with MSI-H tumors had a significantly higher probability of receiving ICIs than those with microsatellite stable (MSS) tumors (odds ratio [OR], 22.66 [95% CI, 17.30-29.73]; P < .001), whereas patients initially diagnosed with synchronous mCRC had significantly lower odds of receiving ICIs than patients with metachronous mCRC (OR, 0.57 [95% CI, 0.45-0.73]; P < .001). Patients with MSI-H tumors who received ICIs as first line of therapy had significantly longer OS than those receiving chemotherapy only (HR, 0.37 [95% CI, 0.25-0.56]; P < .001). Among patients with MSS tumors, ICI-based therapy was associated with significantly longer OS for patients with high albumin level (vs low: HR, 0.28 [95% CI, 0.18-0.45]; P < .001) and antibiotic use (vs nonuse: HR, 0.43 [95% CI, 0.27-0.67]; P < .001), but a significantly shorter OS for patients with synchronous mCRC (vs metachronous: HR, 1.90 [95% CI, 1.24-2.89]; P = .003). In addition, 29 out of 235 patients with MSS tumors (12.3%) experienced durable responses on ICI-based therapy. Similar patterns of associations with TTD were observed.Conclusions and RelevanceIn this cohort study of patients with mCRC, clinical characteristics were associated with different survival outcomes in patients treated with ICI-based therapy, with important clinical implications for patients with MSS tumors who are generally unresponsive to immunotherapy.