Khar A, Pardhasaradhi B V, Varalakshmi C, Ali A M, Kumari A L
Centre for Cellular and Molecular Biology, Hyderabad, India.
Cell Immunol. 1997 Aug 25;180(1):29-35. doi: 10.1006/cimm.1997.1163.
AK-5, which is a spontaneously regressing rat histiocytoma, is killed by necrosis (perforin mediated) and apoptosis. We have studied the induction of apoptosis in AK-5 tumor cells by each of the following: a factor from anti-AK-5 antiserum, dexamethasone, and natural killer cells. Partial inhibition in apoptosis was observed when AK-5 cells were transfected with Crm A gene, a specific inhibitor of ICE protease. Similarly peptide inhibitors Ac-YVAD-cmk and Ac-DEVD-CHO inhibited partially the formation of nuclear bodies and DNA fragmentation induced by each of the above-mentioned apoptotic inducers. Although NK cells were able to kill Crm A and bcl-2 transfected clones by cytotoxic action, they failed to induce DNA fragmentation in these clones, suggesting a dual mode of action by NK cells in the induction of target cell death. We were unable to detect ICE and YAMA/CPP32 transcripts in control AK-5 cells, but upon induction of the apoptotic process, there was significant expression of these transcripts in AK-5 cells. When bcl-2 gene was introduced into AK-5 cells there was complete inhibition of apoptosis, suggesting its affect to be upstream of ICE and YAMA proteases. These results suggest an important role for cysteine proteases in the execution of apoptosis, leading to tumor cell death and the regression of AK-5 tumor in syngeneic hosts.
AK-5是一种可自发消退的大鼠组织细胞瘤，可通过坏死（穿孔素介导）和凋亡被杀死。我们研究了以下各项对AK-5肿瘤细胞凋亡的诱导作用：抗AK-5抗血清中的一种因子、地塞米松和自然杀伤细胞。当用ICE蛋白酶的特异性抑制剂Crm A基因转染AK-5细胞时，观察到凋亡受到部分抑制。同样，肽抑制剂Ac-YVAD-cmk和Ac-DEVD-CHO也部分抑制了上述每种凋亡诱导剂所诱导的核小体形成和DNA片段化。尽管自然杀伤细胞能够通过细胞毒性作用杀死转染了Crm A和bcl-2的克隆，但它们未能在这些克隆中诱导DNA片段化，这表明自然杀伤细胞在诱导靶细胞死亡中具有双重作用模式。我们在对照AK-5细胞中未能检测到ICE和YAMA/CPP32转录本，但在诱导凋亡过程后，AK-5细胞中这些转录本有显著表达。当将bcl-2基因导入AK-5细胞时，凋亡完全受到抑制，这表明其作用在ICE和YAMA蛋白酶的上游。这些结果表明半胱氨酸蛋白酶在凋亡执行过程中起重要作用，导致肿瘤细胞死亡以及同基因宿主中AK-5肿瘤的消退。
