Background: Progranulin (PGRN), as a multifunctional growth factor, is overexpressed in multiple tumors, but the role of PGRN on tumor immunity is still unclear. Here, we studied the effect of PGRN on breast cancer tumor immunity and its possible molecular mechanism. Methods: The changes of macrophage phenotypes after PGRN treatment were detected by western blot, quantitative polymerase chain reaction (PCR) and flow cytometry. Western blot was used to study the signal molecular mechanism of PGRN regulating this process. The number and localization of immune cells in Wild-type (WT) and PGRN^−/− breast cancer tissues were analyzed by immunohistochemical staining and immunofluorescence techniques. The activation and proliferation of CD8⁺ T cells were measured by flow cytometry. Results: After being treated with PGRN, the expressions of M2 markers and programmed death ligand 1 (PD-L1) on macrophages increased significantly. Signal transducer and activator of transcription 3 (STAT3) signaling pathway inhibitor Stattic significantly inhibited the expression of PD-L1 and M2 related markers induced by PGRN. In WT group, CD8 were co-localized with macrophages and PD-L1, but not tumor cells. The number of immune cells in PGRN^−/− breast cancer tissue increased, and their infiltration into tumor parenchyma was also enhanced. Moreover, in the co-culture system, WT peritoneal macrophages not only reduced the ratio of activated CD8⁺ T cells but also reduced the proportion of proliferating CD8⁺ T cells. The addition of programmed death receptor 1 (PD-1) and PD-L1 neutralizing antibodies effectively reversed this effect and restored the immune function of CD8⁺ T cells. Conclusion: These results demonstrate that PGRN promotes M2 polarization and PD-L1 expression by activating the STAT3 signaling pathway. Furthermore, through PD-1/PD-L1 interaction, PGRN can promote the breast tumor immune escape. Our research may provide new ideas and targets for clinical breast cancer immunotherapy.

As CRISPR technology is promoted to more fine-divided molecular biology applications, its inherent performance finds it increasingly difficult to cope with diverse needs in these different fields, and how to more accurately control the performance has become a key issue to develop CRISPR technology to a new stage. Herein, we propose a CRISPR/Cas12a regulation strategy based on the powerful programmability of nucleic acid nanotechnology. Unlike previous difficult and rigid regulation of core components Cas nuclease and crRNA, only a simple switch of different external RNA accessories is required to change the reaction kinetics or thermodynamics, thereby finely and almost steplessly regulating multi-performance of CRISPR/Cas12a including activity, speed, specificity, compatibility, programmability and sensitivity. In particular, the significantly improved specificity is expected to mark advance the accuracy of molecular detection and the safety of gene editing. In addition, this strategy was applied to regulate the delayed activation of Cas12a, overcoming the compatibility problem of the one-pot assay without any physical separation or external stimulation, and demonstrating great potential for fine-grained control of CRISPR. This simple but powerful CRISPR regulation strategy without any component modification has pioneering flexibility and versatility, and will unlock the potential for deeper applications of CRISPR technology in many finely divided fields.