Increase in transglutaminase 2 expression is associated with NF-κB activation in breast cancer tissues

Activation of NF-κB is reported in breast cancers. NF-κB inhibition in breast cancer cell lines results in an increase in apoptosis. However, the reason for continuous activation of this transcription factor in breast cancer is currently unclear. Interestingly, elevated transglutaminase 2 (TGase 2) expression is additionally observed in breast cancer. Recent studies showed that doxorubicin-resistant cells contain a higher level of TGase 2, compared to doxorubicin-sensitive cells. Moreover, increasing the level of TGase 2 in breast cancer cells by transient transfection leads to decreased expression of the inhibitory subunit of NF-κB (I-κBα), and up regulation of NF-κB activity. Our data show that TGase 2 expression is inversely correlated with the level of I-κBα in breast tumors, implying that the enzyme is responsible for the constitutive activation of NF- κB in breast tumors.