Functional characterization of FAM120A as a novel effector in the progranulin/EphA2 oncogenic axis in bladder cancer.

Abstract

Background: Bladder cancer (BC) is one of the most deadly diseases in the USA, with 84,530 new cases and 17,870 estimated deaths in 2026. The growth factor progranulin is involved in several human pathologies, including frontotemporal dementia (FTD), immune response, and cancer. We showed that in BC, progranulin and its signaling receptor, EphA2, drive tumor cell motility, invasion, and in vivo tumor formation, making it a critical pathway in tumor establishment. However, the molecular mechanisms of progranulin/EphA2 action are still poorly defined.

Methods: Progranulin-dependent EphA2 interactome was explored by proteomic approaches. FAM120A or EphA2 protein levels in BC tissue microarrays (TMAs) and FAM120A protein expression in BC cell lines were analyzed by immunohistochemistry (IHC) and immunoblots, respectively. Progranulin-dependent activation of AKT and ERK1/2 were examined by western immunoblots. EphA2-FAM120A interaction was detected using Co-immunoprecipitation and proximity ligation assays (PLA). In addition, EphA2 and FAM120A colocalization and F-actin cytoskeleton rearrangements were assessed by immunofluorescence. The biological function of FAM120A was determined using lentiviral shRNA approaches, wound healing, motility and invasion, spheroid, soft agar, clonogenic assays, cell cytotoxicity, and in vivo xenograft models.

Result: We conducted proteomic approaches and identified novel progranulin-dependent EphA2 interactors, including FAM120A, which is a scaffold protein with a putative role in oncogenic pathways. We confirmed that the EphA2 and FAM120A interaction was enhanced upon progranulin stimulation, and FAM120A was upregulated in BC tissues. We further demonstrated that FAM120A was critical for progranulin-evoked AKT and ERK1/2 activation, clonogenic capacity, wound healing, motility, invasion, and 3D spheroid formation of BC cell lines. In addition, FAM120A was essential for anchorage-independent growth and in vivo tumorigenesis in xenograft models. In addition, FAM120A depletion sensitized BC cells to cisplatin treatment. Mechanistically, we showed that FAM120A depletion inhibited progranulin-dependent F-actin cytoskeleton rearrangement through ERK1/2 and RhoA-dependent pathways. Furthermore, we demonstrated that progranulin-induced activation of RhoA was inhibited upon FAM120A depletion.

Conclusion: The discovery of FAM120A as an oncogenic progranulin-dependent EphA2 interactor provides novel insights into the progranulin/EphA2 signaling axis and uncovers putative novel targets for BC therapy. Furthermore, FAM120A expression may work as a biomarker with diagnostic and possibly prognostic value in BC.