TTR and cancer: HEK293T cells were co-transfected with the silent luc substrate carrying the CMV-attR-Stop-attL-luc cassette (pAE1855, Fig. 1) and a plasmid expressing int either under the control of the cancer specific hTERT promoter (pNA1263) or under the constitutive CMV promoter (pNA979) that served as a positive control.