Fer, also known as FES-related, is a protein-tyrosine kinase. In plants, Feronia (FER) is a malectin-like receptor kinase that plays a crucial role in plant immune signaling. It acts as a RALF-regulated scaffold, modulating the assembly of receptor kinase complexes related to plant immunity [1,3,7]. In animals, Fer and its variant FerT are non-receptor tyrosine kinases involved in cancer progression, metastasis, and sperm function [2]. Fer is also implicated in hematopoietic cell development, survival, migration, and inflammatory mediator release in the hematopoietic system [4].

In breast cancer, high expression of the non-receptor tyrosine kinase Fer is associated with poor survival. Inhibition of Fer kinase activity in MDA-MB-231 cells reduces migration, invasion, and metastasis in a mouse model. Ski family transcriptional corepressor 1 (SKOR1) was identified as a direct Fer kinase substrate, and its loss phenocopies Fer inhibition, affecting breast cancer growth and metastasis in mice [5]. In Drosophila, overexpression of Fer triggered cell migration and activated JNK signaling, suggesting Fer as a positive regulator of JNK-mediated cell migration [6].

In conclusion, Fer has diverse functions in different organisms. In plants, it is essential for immune signaling and growth-stress response balance. In animals, it is involved in cancer-related processes such as cell migration and metastasis, as well as sperm function and hematopoietic cell regulation. The study of Fer in gene-knockout models, like in breast cancer mouse models, helps to understand its role in disease development, providing potential targets for cancer therapy.