Background: Achaete-scute family bHLH transcription factor 1 (ASCL1) is a master transcription factor involved in neuroendocrine differentiation. ASCL1 is expressed in approximately 10% of lung adenocarcinomas and exerts tumor-promoting effects. However, microRNA (miRNA) profiles regulated by ASCL1 in lung adenocarcinoma cells remain unexplored. Method: We analyzed public database of gene expression profiling (RNA-sequencing and miRNA expression data). We also studied miRNA profiles in ASCL1-positive lung adenocarcinoma cells and identified a subset of miRNAs downregulated by ASCL1 knockdown. We examined functions of genes suppressed by miRNAs in ASCL1-positive lung adenocarcinoma cell line, VMRC-LCD. Result: We identified miRNA profiles in ASCL1-positive lung adenocarcinomas and found several miRNAs closely associated with ASCL1 expression, including miR-375, miR-95-3p/miR-95-5p, miR-124-3p, and members of the miR-17~92 family. Similar to small cell lung cancer, Yes1 associated transcriptional regulator (YAP1), a representative miR-375 target gene, is suppressed in ASCL1-positive lung adenocarcinomas. ASCL1 knockdown followed by miRNA profiling in a cell culture model further revealed that ASCL1 positively regulates miR-124-3p and members of the miR-17~92 family. Integrative transcriptomic analyses identified the RNA-binding protein zinc finger protein 36 like 1 (ZFP36L1) as a target gene of miR-124-3p, and immunohistochemical studies have demonstrated that ASCL1-positive lung adenocarcinomas are associated with low ZFP36L1 protein levels. Cell culture studies have shown that ectopic ZFP36L1 expression inhibits cell proliferation, survival, and cell cycle progression. Mechanistically, ZFP36L1 negatively regulated tumorigenic genes, including E2F transcription factor 1 (E2F1) and snail family transcriptional repressor 1 (SNAI1), indicating a tumor-suppressing action. Conclusion: Our study revealed that suppression of ZFP36L1 via ASCL1-regulated miR-124-3p could induce tumor-promoting effects, providing evidence that ASCL1-mediated regulation of miRNAs shapes malignant features of ASCL1-positive lung adenocarcinomas. Citation Format: Naoya Miyashita, Takayoshi Enokido, Masafumi Horie, Hiroshi I. Suzuki, Rei Matsuki, Hans Brunnström, Patrick Micke, Takahide Nagase, Akira Saito. Distinct microRNA signature and suppression of ZFP36L1 define ASCL1-positive lung adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr LB259.

Temsirolimus is an inhibitor of mammalian target of rapamycin and interstitial lung disease (ILD) is known to be one of the adverse events associated with temsirolimus, which usually improves rapidly after discontinuation of the drug and rarely worsens thereafter. Herein, we report a case of delayed exacerbation of ILD after discontinuation of temsirolimus for metastatic renal cell carcinoma in an 86-year-old male with chronic ILD. The patient developed gradually worsening dyspnea five weeks after an initiation of temsirolimus and was admitted to our facility. On his admission, although a pulmonary function test revealed a decreased diffusion capacity, there was no obvious progression of ILD on HRCT scan. His dyspnea once improved after discontinuation of temsirolimus, but it recurred and acute exacerbation of ILD was diagnosed 40 days after his last administration of temsirolimus. He received high-dose steroid therapy, however, he deteriorated and died. Histopathological examination of the lungs at autopsy revealed overlapping diffuse alveolar damage with chronic interstitial changes. In the present case, since there were no specific factors that could have caused acute exacerbation of ILD except for temsirolimus, it was considered to contribute to the exacerbation of underlying ILD. In conclusion, physicians should be aware of the possibility of temsirolimus-induced ILD not only while the medication is administered, but also even after it is discontinued. It is important to carefully interview the patient and to recognize the value of physiological tests, such as respiratory function tests and blood gas analysis, as well as imaging findings on HRCT.

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A 37‐year‐old man was admitted to our hospital with chest pain and fever. Computed tomography showed pleural effusion and irregularly marginated, elevated lesions inside diffuse pleural thickening. Detailed medical examination showed swelling of the left testicle. 18F‐fluorodeoxyglucose positron emission tomography showed uptakes at the thickened pleura and left testis. Pelvic magnetic resonance imaging showed a mass in the left testis with a heterogeneous and partially calcified tumour present interiorly. Thoracoscopy was performed under local anaesthesia, enabling the observation of masses at the pleura and biopsy of the mass, which was diagnosed as malignant pleural mesothelioma. The affected testicle was resected and diagnosed as tunica vaginalis testis mesothelioma. Thus, simultaneous tunica vaginalis testis and pleural mesothelioma were diagnosed. It is necessary to closely examine parts of the body other than the chest.