GDF15 and idiopathic pulmonary fibrosis: Consistent with higher levels of P16 expression, levels of gene expression for our top biomarkers including CCL11 (eotaxin), CCL17 (TARC), CCL18 (PARC), CCL22 (MDC), GDF15, and MMP7 were also significantly higher in lung biospecimens from IPF compared to control participants (all p < 0.001) (Fig. 7).