HOTAIR and cancer: The MAPK signalling pathway has been proven to be abnormally activated in various malignant tumours and closely related to tumour proliferation, invasion, metastasis and drug resistance.32–34 Previous studies verified ERK as a downstream target gene of hepaCAM that plays a key role in the metastasis of PCa by affecting ECM degradation and neovascularisation in malignant tumours.35 Here, we found that HOTAIR promotes invasion and metastasis by activating the MEK/ERK axis with inhibited expression of hepaCAM.