HOPX and cancer: HOXC11, HOXC10 and MNX1 each contain a homeobox domain, and HOTAIR is an antisense RNA whose source locus is found within a cluster of HOXC genes, between HOXC11 and HOXC12. Homeodomain proteins function as transcription factors, regulating gene expression and cell differentiation during development, and have been frequently associated with cancer progression, where they are either up or down regulated, depending on the Hox family member and cancer type.