We used a NSCLC adenocarcinoma PDX chosen specifically for its high expression of the CPS1 biomarker and demonstrated (1); DEX as a single agent can inhibit PDX growth (2), DEX elicits upregulation of CDKN1C (3), DEX results in apoptotic response with appearance of cleaved PARP and (4) DEX does not interfere with platinum toxicity and in fact may be additive as seen in cell line xenograft experiments. This evidence concerns the gene CPS1 and adenocarcinoma.