Hence, further investigation of this synergistic mechanism in unresectable HCC patients with more complicated tumor heterogeneity merits more attention. We wish to thank the authors again for their attention to our research. Footnotes Contributors: KL drafted the manuscript; all authors reviewed and proofread it prior to submission. Funding: This work was Procaine HCl supported by: National Natural Science Foundation of China (No. to enhance the antitumor efficacy of PD-1 antibody in HCC” in volume 11, e006329. We are very grateful to the authors for their letter in which they present some suggestions regarding the establishment of a mouse hepatocellular carcinoma (HCC) tumor model.1 We believe that these new insights are Procaine HCl valuable and worthy of careful consideration by many researchers. The letter mainly focuses on two issues: (1) whether the Hepa1-6 tumor model selected for this study was appropriate and (2) whether subcutaneous tumor models used for evaluating anti-PD-1 efficacy were suitable. Here, we respond to the letter authors. Hepa1-6 is one of the classic cell lines for establishing a mouse HCC model and has been widely used for the investigation of the tumor immune microenvironment (TIME) of HCC by numerous laboratories around the world.2C13 Undoubtedly, human HCC features a highly heterogeneous TIME,14 15 and it is impossible to replicate it using any mouse tumor model with complete accuracy.16 The authors mentioned that Won Jin Ho reported that this TIBx tumor model more closely simulated the immunosuppressive TIME of human HCC, and we certainly believe this is an excellent suggestion. However, the application of the TIBx model to immuno-oncology research seems to have been reported relatively infrequently thus far. In addition, we observed that this Hepa1-6 tumor model exhibited severe TIME hypoxia and adequate infiltration of the main immune VAV1 cell subsets, including immunosuppressive M2-like macrophages and regulatory T cells, which met our experimental needs. Therefore, we selected the orthotopic Hepa1-6 model for the TIME survey; of course, it will be necessary to introduce the TIBx model into our subsequent research. For anti-PD-1 sensitization experiments, we are of Procaine HCl the opinion that this subcutaneous tumor model has multiple advantages because it is usually convenient for tumor inoculation, rechallenge, standardization, and dynamic volume measurement. In fact, numerous studies have also adopted a subcutaneous model to assess the therapeutic effect of monoclonal antibodies,17C26 suggesting that it is widely accepted as a Procaine HCl classic tumor model for cancer immunotherapy research. Based on the findings from this mainstream Hepa1-6 HCC tumor model, we propose potential clinical strategies to strengthen anti-PD-1 therapeutic efficacy. Hence, further investigation of Procaine HCl this synergistic mechanism in unresectable HCC patients with more complicated tumor heterogeneity merits more attention. We wish to thank the authors again for their attention to our research. Footnotes Contributors: KL drafted the manuscript; all authors reviewed and proofread it prior to submission. Funding: This work was supported by: National Natural Science Foundation of China (No. 81800559). Competing interests: None declared. Provenance and peer review: Commissioned; externally peer reviewed. Ethics statements Patient consent for publication Not applicable. Ethics approval Not applicable..