HCLS1, also known as HS1, is a versatile actin-binding protein in leukocytes. It is involved in dynamic actin remodeling processes, which are crucial for leukocytes to carry out functions like adhesion, migration, phagocytosis, and granule release. HS1 is also important for the activation of GTPases and integrins, and mediates signaling downstream of many receptors including BCR, TCR, and CXCR4 [1].

In myelopoiesis, HCLS1 is highly expressed in human myeloid cells. G-CSF stimulation leads to HCLS1 phosphorylation. HCLS1 binds the transcription factor LEF-1, transporting it into the nucleus upon G-CSF stimulation and inducing LEF-1 autoregulation. HCLS1-deficient mice are neutropenic, demonstrating the importance of HCLS1 in myelopoiesis in vivo [3]. In lung adenocarcinoma, HCLS1 expression is downregulated in samples, and low HCLS1 expression is independently associated with poor overall survival. The HCLS1 high-expression group has higher immune-related gene expression and is positively correlated with the infiltration of multiple immune cell types [2].

In conclusion, HCLS1 plays essential roles in leukocyte function and myelopoiesis. Its deficiency in mouse models leads to neutropenia, highlighting its significance in granulocyte production. In lung adenocarcinoma, HCLS1 shows potential as a prognostic biomarker related to immune cell infiltration in the tumor microenvironment, contributing to our understanding of this disease.