MTCP1 (mature T cell proliferation 1) is an oncogene located on chromosome X that functions as a protein kinase activator, specifically enhancing phosphorylation and activation of AKT1 and AKT2 kinases. The gene plays a critical role in cellular proliferation and differentiation, with overexpression inducing increased cell proliferation and partial blockage of cell differentiation 1. MTCP1 is most notably associated with T-cell prolymphocytic leukemia (T-PLL), where chrX translocations involving T-cell receptor genes activate MTCP1 expression and contribute to disease pathogenesis 2. The gene can be activated through various mechanisms, including t(X;7) translocations that juxtapose TCRB segments to MTCP1, activating cryptic promoters 3. Recent studies have expanded MTCP1's oncogenic role beyond T-cell malignancies, demonstrating its involvement in chrX lymphocytic leukemia when overexpressed in B-cells 4, and in myeloid neoplasms through fusion genes like GATAD2B::MTCP1 and KANSL1-MTCP1 that dysregulate MTCP1 expression 51. These findings establish MTCP1 as a versatile oncogene whose aberrant activation through chrX rearrangements drives proliferation and blocks differentiation across multiple hematologic malignancies, making it a potential therapeutic target.