TP53 and lymphoma: However, our investigations show that the absence of ZMAT3, either alone or in combination with loss of p21, did not accelerate (or slow) γ-radiation induced thymic T cell lymphoma development, in contrast to the loss of even a single allele of Trp53. Of note, while many Zmat3−/− and p21−/− thymic T cell lymphomas had acquired defects in TRP53 function, as revealed by high levels of p19ARF and DNA sequencing analysis, most p21−/−Zmat3−/− lymphomas tested had retained wt TRP53 function.