Panoply™ Human TGM2 Over-expressing Stable Cell Line

Transglutaminase 2 (TG2, also known as TGM2) is a protein expressed in various tissues that performs diverse-and sometimes even contradictory-intracellular and extracellular functions under both physiological and pathophysiological conditions. During tumor progression, TG2 has been implicated in various biological processes, including cell adhesion, DNA repair mechanisms, the induction of apoptosis, and mesenchymal transdifferentiation. In this study, researchers investigated whether TG2 contributes to radioresistance in two human melanoma cell lines (A375 and MeWo). To this end, they modulated intracellular TG2 biosynthesis and activity through transfection-induced overexpression, gene knockout, and the use of a selective TG2 inhibitor. The results showed that the proliferation and clonogenic capacity of TG2-overexpressing cells did not exceed those of wild-type cells, indicating that increased TG2 biosynthesis does not further enhance the radioresistance of melanoma cells. Conversely, knocking out TG2 in A375 cells reduced their post-irradiation proliferation, clonogenic capacity, and spheroid growth, confirming that TG2 indeed contributes to radioresistance in melanoma cells. Given that the biosynthesis of TG1, TG3, and some TG6 was detected in both A375 and MeWo cells, it is hypothesized that these other members of the TG family may exert a compensatory effect.

Seventy-two hours after exposure to 2 Gy or 4 Gy radiation, A375-TG2 cells (TG2-overexpressing A375 cells) exhibited enhanced proliferative capacity compared to A375-WT and control cells, although this difference was not observed at the 24-hour time point. However, calculations indicated that the doubling times for all A375 sublines were comparable (Figure 1A). Results regarding the clonal expansion of A375-TG2 cells under radiation exposure were inconsistent: at a low radiation dose (0.5 Gy), clonal expansion increased relative to A375-WT and control cells; conversely, at higher doses, clonal expansion capacity was reduced (2 Gy) or remained similar (4 Gy) compared to A375-WT cells (Figure 1B). Compared to the non-irradiated control group (0 Gy), intracellular TG2 biosynthesis levels in A375-TG2 cells increased 24 hours after exposure to 0.5 Gy and 2 Gy radiation. This effect was no longer evident at 72 hours post-irradiation and was not observed in A375-WT or control cells at any time point (Figure 1C). Correspondingly, comparisons between A375-TG2 cells and A375-WT or control cells under identical radiation doses revealed elevated TG2 biosynthesis levels at 0.5 Gy and 2 Gy.

Figure 1. Proliferation, clonal expansion and TG2 biosynthesis of melanoma sub-cell lines after irradiation. (Aepler J, et al., 2022)