MARCHF9, also known as membrane-associated ring-CH-type finger 9, is a RING-type E3 ubiquitin transferase. It plays crucial roles in multiple biological processes. It is involved in the regulation of autophagy through the MARCHF9-ATG9A axis, which is related to Golgi integrity and dynamics [1]. Also, it participates in the regulation of immune-related responses, such as influencing the intracellular transport of major histocompatibility complex class I (MHC I) from the trans-Golgi network (TGN) by ubiquitination [4], and ubiquitination of HLA-DO along with other MARCH family E3 ligases [5].

In colorectal cancer, high MARCHF9 expression is associated with advanced clinical stages, distant metastases, and poor survival outcomes. Knockdown of MARCHF9 in COAD cell lines inhibits cell proliferation and invasion, revealing its oncogenic role in this cancer type [2]. In lung adenocarcinoma, MARCHF9 is down-regulated in tumor tissues compared to normal lung tissues. Overexpression of MARCHF9 in relevant cell lines attenuates tumor migration and invasion, suggesting it may suppress tumor progression by down-regulating ICAM-1 signaling [3].

In conclusion, MARCHF9 is an important E3 ubiquitin transferase involved in autophagy-related Golgi regulation and immune-related processes. Its role in promoting colorectal cancer progression and suppressing lung adenocarcinoma progression as revealed by functional studies indicates its significance in cancer research. These findings from in vitro and in vivo-like cell-based models contribute to understanding the mechanisms of cancer development and potentially offer new therapeutic targets.