TBC1D8 is a TBC domain-containing protein that functions as a GTPase-activating protein for Rab family proteins 1. The protein contains a catalytic TBC domain with dual finger residues (Arg538 and Gln573) that mediates its enzymatic activity 1. A human-specific 446-bp insertion in the TBC1D8B ortholog enhances gene expression and promotes cell proliferation and migration 1. TBC1D8 has multifaceted disease relevance. In colorectal cancer, elevated TBC1D8 expression independently predicts poor prognosis and correlates with hypoxia and M2 macrophage infiltration 2. In pancreatic cancer, TBC1D8 expression in peripheral blood mononuclear cells contributes to a diagnostic gene signature distinguishing patients from healthy controls 34. Additionally, TBC1D8 genetic variants associate with progressive supranuclear palsy tau neuropathology 5, hearing loss susceptibility 6, male infertility due to non-obstructive azoospermia involving defective spermatid formation 7, and atherosclerosis risk through gene-smoking interactions 8. Clinically, TBC1D8 represents a potential biomarker for cancer diagnosis and prognosis, with expression profiling offering diagnostic utility beyond conventional markers like CA19-9 4.