Which translocation is associated with Philadelphia chromosome and has a poor prognosis in ALL?

The Philadelphia chromosome is specifically associated with the translocation t(9;22), which results in the BCR-ABL fusion gene. This gene codes for a constitutively active tyrosine kinase that plays a critical role in the pathogenesis of chronic myelogenous leukemia (CML) and, more importantly, is linked to a poor prognosis in acute lymphoblastic leukemia (ALL) as well.

In ALL, the presence of the Philadelphia chromosome is a marker for a more aggressive disease and is associated with high-risk features, leading to a poorer response to standard chemotherapy regimens compared to other genetic subtypes. The activation of the BCR-ABL fusion protein promotes increased proliferation of leukemic cells and inhibits normal apoptosis, contributing significantly to the poor clinical outcomes observed in patients with this genetic aberration.

In contrast, the other translocations mentioned are associated with different hematological disorders or are generally linked to better prognostic outcomes in ALL. For example, t(12;21) is often seen in pediatric ALL and is usually associated with a more favorable prognosis. The t(14;18) translocation is commonly linked to follicular lymphoma, and the t(11;14) translocation is associated with mantle cell lymphoma, neither of