Furthermore, the ATM-CHK2 pathway has demonstrated involvement in a Sprague–Dawley lung recession/MCT rat model of PAH, in which ATM and its effector substrates demonstrated significantly increased activity during early disease development, but markedly reduced activity compared to controls in the advanced stages of PAH, suggesting the involvement of excessive DNA damage in the early stages of disease progression [20]. Here, CHEK2 is linked to pulmonary arterial hypertension.