Panoply™ Human PDCD1 Over-expressing Stable Cell Line

Doxorubicin (DOX) is a potent chemotherapeutic drug. However, it causes severe cardiac damage in many patients by inducing apoptosis. DOX-induced cardiotoxicity can be attenuated by activated autophagy in the heart. Previous studies have found that programmed cell death 1 (Pdcd1), an immune checkpoint receptor, inhibits DOX-induced cardiomyocyte apoptosis. Here, researchers investigated whether autophagy is involved in the protective effect of Pdcd1 against DOX-induced cardiomyocyte apoptosis. The study showed that Pdcd1 overexpression activated the autophagic pathway by inhibiting the mammalian target of rapamycin, a major negative regulator of autophagy. In addition, it prevented doxorubicin-induced cardiomyocyte apoptosis. Similar cardioprotective effects were observed when normal H9c2 cells (not overexpressing Pdcd1) were treated with the autophagy inducer rapamycin before doxorubicin treatment. In contrast, in cancer cells, Pdcd1 overexpression increased basal apoptosis and doxorubicin-induced apoptosis. The roles of Pdcd1 in doxorubicin-induced apoptosis in cardiomyocytes and cancer cells were opposite. Pdcd1 signaling prevented doxorubicin-induced cardiomyocyte apoptosis by inducing autophagy; it enhanced doxorubicin-induced cancer cell apoptosis. Therefore, Pdcd1 may be a key molecule for more effective and safer DOX chemotherapy.

To investigate the role of Pdcd1 in doxorubicin (DOX)-induced apoptosis of cancer cells, Pdcd1 overexpression plasmids were transfected into K562 and MCF-7 cells (Figure 1). In the Pdcd1-overexpressing K562 cancer cells, the basal levels of caspase-3/7 activity and apoptosis were significantly increased even in the absence of DOX. In control (mock) cells, DOX-induced caspase-3/7 activity and apoptosis increased in a concentration-dependent manner (Figure 1a, b). In Pdcd1-overexpressing cells, DOX-induced apoptosis was further enhanced (Figure 1b). Alternatively, in addition to K562 cells, Pdcd1-overexpressing MCF-7 cells also exhibited an apoptosis-inducing effect, as determined by the luminescence intensity of Annexin V (Figure 1c) and morphological observation of the nucleus (Figure 1d, e). DOX enhanced apoptosis induction in Pdcd1-overexpressing cells; this enhancement was particularly significant when the degree of apoptosis was assessed by changes in nuclear morphology, i.e., chromatin condensation and division into multiple bodies (Figure 1d). These results suggest that Pdcd1 signaling can both promote apoptosis induction and enhance DOX-induced apoptosis in K562 and MCF-7 cells. Thus, the role of Pdcd1 in regulating apoptosis in cancer cells is opposite to that in H9c2 cardiomyocytes.

Figure 1. Effects of Pdcd1 overexpression on doxorubicin (DOX)-induced apoptosis in human cancer cell lines, K562 (human erythroleukemia cells) and MCF-7 (human breast cancer cells). (Kanno S, Hara A., 2022)