Purpose Histologic transformation of EGFR mutant lung adenocarcinoma (LADC) into small-cell lung cancer (SCLC) has been described as one of the major resistant mechanisms for epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs). However, the molecular pathogenesis is still unclear. Methods We investigated 21 patients with advanced EGFR-mutant LADCs that were transformed into EGFR TKI-resistant SCLCs. Among them, whole genome sequencing was applied for nine tumors acquired at various time points from four patients to reconstruct their clonal evolutionary history and to detect genetic predictors for small-cell transformation. The findings were validated by immunohistochemistry in 210 lung cancer tissues. Results We identified that EGFR TKI-resistant LADCs and SCLCs share a common clonal origin and undergo branched evolutionary trajectories. The clonal divergence of SCLC ancestors from the LADC cells occurred before the first EGFR TKI treatments, and the complete inactivation of both RB1 and TP53 were observed from the early LADC stages in sequenced tumors. We extended the findings by immunohistochemistry in the early-stage LADC tissues of 75 patients treated with EGFR TKIs; inactivation of both Rb and p53 was strikingly more frequent in the small-cell-transformed group than in the nontransformed group (82% v 3%; odds ratio, 131; 95% CI, 19.9 to 859). Among patients registered in a predefined cohort (n = 65), an EGFR mutant LADC that harbored completely inactivated Rb and p53 had a 43× greater risk of small-cell transformation (relative risk, 42.8; 95% CI, 5.88 to 311). Branch-specific mutational signature analysis revealed that apolipoprotein B mRNA editing enzyme, catalytic polypeptide-like (APOBEC)-induced hypermutation was frequent in the branches toward small-cell transformation. Conclusion EGFR TKI-resistant SCLCs are branched out early from the LADC clones that harbor completely inactivated RB1 and TP53. The evaluation of RB1 and TP53 status in EGFR TKI-treated LADCs is informative in predicting small-cell transformation.

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Highlights d Driver fusion oncogenes in LADCs are generated from complex genomic rearrangements d These rearrangements are frequently copy-number balanced, resembling germline events d Fusions often arise in early decades of life, leaving long latency to diagnosis d SETD2 inactivation is cooperative with fusion oncogenes in TP53-wild-type LADCs

Nonalcoholic fatty liver disease (NAFLD) is increasing in worldwide prevalence, closely tracking the obesity epidemic, but specific pharmaceutical treatments for NAFLD are lacking. Defining the key molecular pathways underlying the pathogenesis of NAFLD is essential for developing new drugs. Here we demonstrate that inhibition of gut-derived serotonin synthesis ameliorates hepatic steatosis through a reduction in liver serotonin receptor 2A (HTR2A) signaling. Local serotonin concentrations in the portal blood, which can directly travel to and affect the liver, are selectively increased by high-fat diet (HFD) feeding in mice. Both gut-specific Tph1 knockout mice and liver-specific Htr2a knockout mice are resistant to HFD-induced hepatic steatosis, without affecting systemic energy homeostasis. Moreover, selective HTR2A antagonist treatment prevents HFD-induced hepatic steatosis. Thus, the gut TPH1-liver HTR2A axis shows promise as a drug target to ameliorate NAFLD with minimal systemic metabolic effects.

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Background and Aims Targeting costimulatory receptors with agonistic antibodies is a promising cancer immunotherapy option. We aimed to investigate costimulatory receptor expression, particularly 4‐1BB (CD137 or tumor necrosis factor receptor superfamily member 9), on tumor‐infiltrating CD8+ T cells (CD8+ tumor‐infiltrating lymphocytes [TILs]) and its association with distinct T‐cell activation features among exhausted CD8+ TILs in hepatocellular carcinoma (HCC). Approach and Results Tumor tissues, adjacent nontumor tissues, and peripheral blood were collected from HCC patients undergoing surgical resection (n = 79). Lymphocytes were isolated and used for multicolor flow cytometry, RNA‐sequencing, and in vitro functional restoration assays. Among the examined costimulatory receptors, 4‐1BB was most prominently expressed on CD8+ TILs. 4‐1BB expression was almost exclusively detected on CD8+ T cells in the tumor—especially on programmed death 1 (PD‐1)high cells and not PD‐1int and PD‐1neg cells. Compared to PD‐1int and 4‐1BBnegPD‐1high CD8+ TILs, 4‐1BBposPD‐1high CD8+ TILs exhibited higher levels of tumor reactivity and T‐cell activation markers and significant enrichment for T‐cell activation gene signatures. Per‐patient analysis revealed positive correlations between percentages of 4‐1BBpos cells among CD8+ TILs and levels of parameters of tumor reactivity and T‐cell activation. Among highly exhausted PD‐1high CD8+ TILs, 4‐1BBpos cells harbored higher proportions of cells with proliferative and reinvigoration potential. Our 4‐1BB–related gene signature predicted survival outcomes of HCC patients in the The Cancer Genome Atlas cohort. 4‐1BB agonistic antibodies enhanced the function of CD8+ TILs and further enhanced the anti‐PD‐1–mediated reinvigoration of CD8+ TILs, especially in cases showing high levels of T‐cell activation. Conclusion 4‐1BB expression on CD8+ TILs represents a distinct activation state among highly exhausted CD8+ T cells in HCC. 4‐1BB costimulation with agonistic antibodies may be a promising strategy for treating HCCs exhibiting prominent T‐cell activation.

Highlights (maximum 85 characters, including spaces) 1. Absence of macrophages results in zigzag shaped pupils. 2. Macrophages do not prune pupillary membrane vessels during postnatal first week. 3. Macrophages engulf pigmented debris in pupillary edges. 4. Irises protrude between blood vessels in the absence of macrophages.

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