STX12 and neoplasm: Furthermore, expression of PRDX6, PLCβ4 and STX12 was upregulated in erlotinib-treated PC9+GFP tumours and was downregulated in erlotinib-treated PC9+pre-miR-371 tumours, suggesting that downregulation of these genes contributes to tumour regression and prevention of tumour regrowth during drug treatment (Fig. 4e).