Radixin modulates the plasma membrane localization of CD47 in human uterine cervical adenocarcinoma cells

Ezrin works as a scaffold protein for a macrophage checkpoint molecule CD47, leading to a poor prognosis for patients with uterine cervical squamous cell carcinoma

OBJECTIVES

Despite recent advances in the immunotherapeutic intervention as the second-line treatment of cervical cancer, including Pembrolizumab and Nivolumab, the advanced stages of the disease are still associated with poor prognosis. CD47 is a macrophage checkpoint molecule overexpressed superficially in nearly all cancer types that binds to its receptor on macrophage surface, leading to a disruption of their phagocytic capacities against cancer cells. Ezrin-Radixin-Moesin (ERM) family member of proteins work as scaffold proteins by crosslinking specific transmembrane proteins to actin filaments, contributing to their plasma membrane localization. This study aimed to investigate the relationship between ERM family and CD47 in the uterine cervical squamous cell carcinoma (UCSCC).

MATERIALS AND METHODS

The mRNA expression, intracellular localization, and molecular interaction of CD47 and ERM in BOKU cells derived from human UCSCC were determined using RT-PCR, immunofluorescence, and co-immunoprecipitation, respectively. CD47 plasma membrane expression was measured by flow cytometry three days after transfection with small interfering RNAs against each ERM. CD47 and ERM expression in tumor tissues from patients with uterine cervical cancer was analyzed using a clinical RNA sequencing database.

RESULTS

Confocal laser scanning microscopy analysis showed the co-localization of CD47 with all three ERM in the plasma membrane of BOKU cells. RNA interference-mediated knockdown of ezrin but not others reduced the plasma membrane expression of CD47. Furthermore, immunoprecipitation assay demonstrated the molecular interaction of CD47 with ezrin. Notably, bioinformatic analysis indicated that CD47 and ezrin expressions were markedly increased and positively correlated in the clinical uterine cervical tumor tissues and that higher expressions of ezrin correlates with a poor prognosis for the uterine cervical cancers.

CONCLUSION

This study illustrates that in uterine cervical cancers, ezrin may be a dominant scaffold protein responsible for CD47 expression and, therefore, is a potential target for developing a novel macrophage checkpoint blockade therapy.

Radixin: Roles in the Nervous System and Beyond

BACKGROUND

Radixin is an ERM family protein that includes radixin, moesin, and ezrin. The importance of ERM family proteins has been attracting more attention, and studies on the roles of ERM in biological function and the pathogenesis of some diseases are accumulating. In particular, we have found that radixin is the most dramatically changed ERM protein in elevated glucose-treated Schwann cells.

METHOD

We systemically review the literature on ERM, radixin in focus, and update the roles of radixin in regulating cell morphology, interaction, and cell signaling pathways. The potential of radixin as a therapeutic target in neurodegenerative diseases and cancer was also discussed.

RESULTS

Radixin research has focused on its cell functions, activation, and pathogenic roles in some diseases. Radixin and other ERM proteins maintain cell shape, growth, and motility. In the nervous system, radixin has been shown to prevent neurodegeneration and axonal growth. The activation of radixin is through phosphorylation of its conserved threonine residues. Radixin functions in cell signaling pathways by binding to membrane proteins and relaying the cell signals into the cells. Deficiency of radixin has been involved in the pathogenic process of diseases in the central nervous system and diabetic peripheral nerve injury. Moreover, radixin also plays a role in cell growth and drug resistance in multiple cancers. The trials of therapeutic potential through radixin modulation have been accumulating. However, the exact mechanisms underlying the roles of radixin are far from clarification.

CONCLUSIONS

Radixin plays various roles in cells and is involved in developing neurodegenerative diseases and many types of cancers. Therefore, radixin may be considered a potential target for developing therapeutic strategies for its related diseases. Further elucidation of the function and the cell signaling pathways that are linked to radixin may open the avenue to finding novel therapeutic strategies for diseases in the nervous system and other body systems.

Moesin affects the plasma membrane expression and the immune checkpoint function of CD47 in human ovarian clear cell carcinoma

Among major histological subtypes of epithelial ovarian cancer, a higher incidence of ovarian clear cell carcinoma (OCCC) is observed in East Asian populations, particularly in Japan. Despite recent progress in the immune checkpoint inhibitors for a wide variety of cancer cell types, patients with OCCC exhibit considerably low response rates to these drugs. Hence, urgent efforts are needed to develop a novel immunotherapeutic approach for OCCC. CD47, a transmembrane protein, is overexpressed in almost all cancer cells and disrupts macrophage phagocytic activity in cancer cells. Ezrin-Radixin-Moesin (ERM) family member of proteins serve as scaffold proteins by crosslinking certain transmembrane proteins with the actin cytoskeleton, contributing to their plasma membrane localization. Here, we examined the role of ERM family in the plasma membrane localization and functionality of CD47 in OCCC cell lines derived from Japanese women. Confocal laser scanning microscopy analysis showed colocalization of CD47 with all three ERM in the plasma membrane of OCCC cells. RNA interference-mediated gene silencing of moesin, but not others, decreased the plasma membrane expression and immune checkpoint function of CD47, as determined by flow cytometry and in vitro phagocytosis assay using human macrophage-like cells, respectively. Interestingly, clinical database analysis indicated that moesin expression in OCCC was higher than that in other histological subtypes of ovarian cancers, and the expression of CD47 and moesin increased with the cancer stage. In conclusion, moesin is overexpressed in OCCC and may be the predominant scaffold protein responsible for CD47 plasma membrane localization and function in OCCC.