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Background Small cell lung cancer (SCLC) is an aggressive lung cancer subtype that is associated with high recurrence and poor prognosis. Due to lack of potential drug targets, SCLC patients have few therapeutic options. MicroRNAs (miRNAs) provide an interesting repertoire of therapeutic molecules; however, the identification of miRNAs regulating SCLC growth and metastasis and their precise regulatory mechanisms are not well understood. Methods To identify novel miRNAs regulating SCLC, we performed miRNA-sequencing from donor/patient serum samples and analyzed the bulk RNA-sequencing data from the tumors of SCLC patients. Further, we developed a nanotechnology-based, highly sensitive method to detect microRNA-1 (miR-1, identified miRNA) in patient serum samples and SCLC cell lines. To assess the therapeutic potential of miR-1, we developed various in vitro models, including miR-1 sponge (miR-1Zip) and DOX-On-miR-1 (Tet-ON) inducible stable overexpression systems. Mouse models derived from intracardiac injection of SCLC cells (miR-1Zip and DOX-On-miR-1) were established to delineate the role of miR-1 in SCLC metastasis. In situ hybridization and immunohistochemistry were used to analyze the expression of miR-1 and target proteins (mouse and human tumor specimens), respectively. Dual-luciferase assay was used to validate the target of miR-1, and chromatin immunoprecipitation assay was used to investigate the protein-gene interactions. Results A consistent downregulation of miR-1 was observed in tumor tissues and serum samples of SCLC patients compared to their matched normal controls, and these results were recapitulated in SCLC cell lines. Gain of function studies of miR-1 in SCLC cell lines showed decreased cell growth and oncogenic signaling, whereas loss of function studies of miR-1 rescued this effect. Intracardiac injection of gain of function of miR-1 SCLC cell lines in the mouse models showed a decrease in distant organ metastasis, whereas loss of function of miR-1 potentiated growth and metastasis. Mechanistic studies revealed that CXCR4 is a direct target of miR-1 in SCLC. Using unbiased transcriptomic analysis, we identified CXCR4/FOXM1/RRM2 as a unique axis that regulates SCLC growth and metastasis. Our results further showed that FOXM1 directly binds to the RRM2 promoter and regulates its activity in SCLC. Conclusions Our findings revealed that miR-1 is a critical regulator for decreasing SCLC growth and metastasis. It targets the CXCR4/FOXM1/RRM2 axis and has a high potential for the development of novel SCLC therapies. Graphical Abstract MicroRNA-1 (miR-1) downregulation in the tumor tissues and serum samples of SCLC patients is an important hallmark of tumor growth and metastasis. The introduction of miR-1 in SCLC cell lines decreases cell growth and metastasis. Mechanistically, miR-1 directly targets CXCR4, which further prevents FOXM1 binding to the RRM2 promoter and decreases SCLC growth and metastasis.

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Lung cancer is the leading cause of cancer-related deaths worldwide. Small cell lung cancer (SCLC) is an aggressive subtype of lung cancer. The overall survival rate of SCLC is dismal owing to early metastasis, chemoresistance, higher rate of recurrence, and lack of available treatment options. Although some immunotherapeutic drugs have been approved for SCLC, they are effective only in a small fraction of the patient population. This necessitates the quest to find promising vulnerabilities against SCLC. Bioinformatic analysis on SCLC data set in the backdrop of various immune checkpoint regulators revealed B7-H3 as a promising target. The bioinformatics data was recapitulated in SCLC cell lines and human SCLC tissues. To delineate the effects of B7-H3 targeting, we performed CRISPR-Cas9 mediated B7-H3 knockout in SCLC cell lines. B7-H3 knockout in SCLC cells showed a decrease in colony formation, migration, and wound healing properties. Our results suggest that deletion of B7-H3 decrease the functional activities and activation of oncogenic signaling pathways, such as Erk, Akt, and Stat3. Further, we assessed if B7-H3 regulates SCLC metabolism. Preliminary data showed that B7-H3 knockout in SCLC cells inhibits glucose uptake, extracellular acidification rate (ECAR), and oxygen consumption rate (OCR), suggesting its role in SCLC metabolic reprogramming. Altogether, our data indicate that B7-H3 plays a crucial role in SCLC pathogenesis and could serve as a potential therapeutic target for SCLC. Citation Format: Mahek Fatima, Parvez Khan, Asad Ur Rehman, Md Arafat Khan, Shailendra Kumar Maurya, Aatiya Ahmad, Mohd Ali Zaidi, Shailendra Gautam, Subodh Lele, Surinder Kumar Batra, Mohd Wasim Nasser. B7-H3 mediated metabolic reprogramming promotes small cell lung cancer progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 289.