Frost P, Ng C P, Belldegrun A, Bonavida B
Department of Microbiology and Immunology, UCLA School of Medicine, USA.
Cell Immunol. 1997 Aug 25;180(1):70-83. doi: 10.1006/cimm.1997.1169.
Several reports suggest that immunotherapy mediated by cytotoxic lymphocytes is beneficial in the destruction of drug-resistant tumor cells. Cytotoxic T lymphocytes kill target cells by two main mechanisms, namely by the perforin pathway and by the Fas-ligand (Fas-L) pathway. The role of the Fas-L pathway in tumor cell killing is not clear because many Fas(+)-expressing tumor cells are resistant to the Fas-L agonist cytotoxic anti-Fas antibody. The human prostate tumor cell lines (PC-3, DU145, and LnCAP) express Fas on the cell surface but are resistant to killing by anti-Fas antibody. This study examined the sensitivity of prostate tumor cells to Fas-L-mediated cytotoxicity and sensitization of the tumor cells by drugs to Fas-L-mediated killing. All three prostate tumor cell lines are resistant to Fas-L killing as determined by the use of the murine CTL hybridoma PMMI that kills only through the Fas-L pathway. However, the addition of subtoxic concentrations of CDDP or VP-16 significantly sensitized the PC-3 and DU145, but not LnCAP, tumor cells to Fas-L killing and apoptosis by PMMI. The sensitization of tumor cells by drugs was inhibited by neutralizing anti-Fas antibody. These findings demonstrate that immunoresistant Fas(+)-expressing DU145 and PC-3 prostate tumor cells can be sensitized by drugs to Fas-L killing. We then examined the role of Fas-L killing by TIL and LAK cells. All three prostate tumor cell lines were sensitive to killing by TIL and LAK and cell killing was primarily mediated through the Ca(2+)-dependent perforin pathway because it was blocked by the addition of EGTA/MgCl2. Sensitization by CDDP or VP-16 did not significantly augment killing of untreated tumor cells by TIL or LAK cells. However, in the presence of EGTA/MgCl2, the addition of CDDP or VP-16 significantly augmented killing of PC-3 and DU145, but not LnCAP, by TIL and LAK, and killing was blocked by neutralizing anti-Fas antibody. These findings demonstrate that both TIL and LAK exhibit a Fas-L-mediated killing pathway that is revealed once the perforin pathway is blocked by the Ca2+ chelator EGTA/MgCl2. Altogether, these findings show that drug-resistant, Fas(+)-expressing PC-3 and DU145 prostate tumor cells can be sensitized by CDDP and VP-16 to killing by Fas-L-bearing CTL, TIL, and LAK cells. Sensitization of tumor cells by drugs may augment the efficacy of immunotherapy in the eradication of tumor cells that are resistant to Fas-L-mediated killing.
几份报告表明，由细胞毒性淋巴细胞介导的免疫疗法有助于破坏耐药肿瘤细胞。细胞毒性T淋巴细胞通过两种主要机制杀死靶细胞，即通过穿孔素途径和Fas配体（Fas-L）途径。Fas-L途径在肿瘤细胞杀伤中的作用尚不清楚，因为许多表达Fas的肿瘤细胞对Fas-L激动剂细胞毒性抗Fas抗体具有抗性。人前列腺肿瘤细胞系（PC-3、DU145和LnCAP）在细胞表面表达Fas，但对抗Fas抗体的杀伤具有抗性。本研究检测了前列腺肿瘤细胞对Fas-L介导的细胞毒性的敏感性以及药物对肿瘤细胞Fas-L介导杀伤的致敏作用。通过使用仅通过Fas-L途径杀伤的小鼠CTL杂交瘤PMMI测定，所有三种前列腺肿瘤细胞系均对Fas-L杀伤具有抗性。然而，添加亚毒性浓度的顺铂（CDDP）或依托泊苷（VP-16）可显著使PC-3和DU145肿瘤细胞对PMMI介导的Fas-L杀伤和凋亡敏感，但对LnCAP肿瘤细胞无效。中和抗Fas抗体可抑制药物对肿瘤细胞的致敏作用。这些发现表明，表达Fas的免疫抗性DU145和PC-3前列腺肿瘤细胞可被药物致敏，从而对Fas-L杀伤敏感。然后，我们检测了肿瘤浸润淋巴细胞（TIL）和淋巴因子激活的杀伤细胞（LAK）的Fas-L杀伤作用。所有三种前列腺肿瘤细胞系对TIL和LAK的杀伤均敏感，细胞杀伤主要通过Ca（2+）依赖性穿孔素途径介导，因为添加乙二醇双四乙酸（EGTA）/氯化镁（MgCl2）可阻断该途径。CDDP或VP-16致敏并未显著增强TIL或LAK细胞对未处理肿瘤细胞的杀伤。然而，在存在EGTA/MgCl2的情况下，添加CDDP或VP-16可显著增强TIL和LAK对PC-3和DU145肿瘤细胞的杀伤，但对LnCAP肿瘤细胞无效，且中和抗Fas抗体可阻断杀伤作用。这些发现表明，一旦穿孔素途径被Ca2+螯合剂EGTA阻断，TIL和LAK均表现出Fas-L介导的杀伤途径。总之，这些发现表明，耐药的、表达Fas的PC-3和DU145前列腺肿瘤细胞可被CDDP和VP-16致敏，从而对携带Fas-L的CTL、TIL和LAK细胞的杀伤敏感。药物对肿瘤细胞的致敏作用可能会增强免疫疗法在根除对Fas-L介导杀伤具有抗性的肿瘤细胞方面的疗效。
