Herz Corinna, Hertrampf Anke, Zimmermann Stefan, Stetter Nadine, Wagner Meike, Kleinhans Claudia, Erlacher Miriam, Schüler Julia, Platz Stefanie, Rohn Sascha, Mersch-Sundermann Volker, Lamy Evelyn
Institute for Environmental Health Sciences and Hospital Infection Control, Freiburg University Medical Center, Freiburg, Germany.
J Cell Mol Med. 2014 Dec;18(12):2393-403. doi: 10.1111/jcmm.12412. Epub 2014 Sep 25.
In contrast to cancer cells, most normal human cells have no or low telomerase levels which makes it an attractive target for anti-cancer drugs. The small molecule sulforaphane from broccoli is known for its cancer therapeutic potential in vitro and in vivo. In animals and humans it was found to be quickly metabolized into 4-methylthiobutyl isothiocyanate (MTBITC, erucin) which we recently identified as strong selective apoptosis inducer in hepatocellular carcinoma (HCC) cells. Here, we investigated the relevance of telomerase abrogation for cytotoxic efficacy of MTBITC against HCC. The drug was effective against telomerase, independent from TP53 and MTBITC also blocked telomerase in chemoresistant subpopulations. By using an orthotopic human liver cancer xenograft model, we give first evidence that MTBITC at 50 mg/KG b.w./d significantly decreased telomerase activity in vivo without affecting enzyme activity of adjacent normal tissue. Upon drug exposure, telomerase decrease was consistent with a dose-dependent switch to anti-survival, cell arrest and apoptosis in our in vitro HCC models. Blocking telomerase by the specific inhibitor TMPyP4 further sensitized cancer cells to MTBITC-mediated cytotoxicity. Overexpression of hTERT, but not enzyme activity deficient DNhTERT, protected against apoptosis; neither DNA damage nor cytostasis induction by MTBITC was prevented by hTERT overexpression. These findings imply that telomerase enzyme activity does not protect against MTBITC-induced DNA damage but impacts signalling processes upstream of apoptosis execution level.
与癌细胞不同，大多数正常人类细胞的端粒酶水平极低或几乎没有，这使其成为抗癌药物的一个有吸引力的靶点。西兰花中的小分子萝卜硫素在体外和体内均具有癌症治疗潜力。在动物和人类中，它被发现能迅速代谢为4-甲基硫代丁基异硫氰酸盐（MTBITC，山嵛菜烯），我们最近将其鉴定为肝细胞癌（HCC）细胞中强大的选择性凋亡诱导剂。在此，我们研究了端粒酶缺失对于MTBITC抗HCC细胞毒性功效的相关性。该药物对端粒酶有效，与TP53无关，并且MTBITC在化疗耐药亚群中也能阻断端粒酶。通过使用原位人肝癌异种移植模型，我们首次证明，MTBITC以50 mg/KG体重/天的剂量显著降低了体内的端粒酶活性，而不影响相邻正常组织的酶活性。在药物处理后，端粒酶的降低与我们体外HCC模型中向抗生存、细胞停滞和凋亡的剂量依赖性转变一致。用特异性抑制剂TMPyP4阻断端粒酶可进一步使癌细胞对MTBITC介导的细胞毒性敏感。hTERT的过表达可保护细胞免受凋亡，但酶活性缺陷的DNhTERT则不能；hTERT过表达并不能阻止MTBITC诱导的DNA损伤或细胞停滞。这些发现表明，端粒酶的酶活性并不能保护细胞免受MTBITC诱导的DNA损伤，但会影响凋亡执行水平上游的信号传导过程。
