Stem-like tumor-initiating cells (TICs) are implicated in cancer progression and recurrence, and can be identified by sphere-formation and tumorigenicity assays. Oncolytic viruses infect, replicate in, and kill a variety of cancer cells. In this study, we seek proof of principle that TICs are susceptible to viral infection. HCT8 human colon cancer cells were subjected to serum-free culture to generate TIC tumorspheres. Parent cells and TICs were infected with HSV-1 subtype NV1066. Cytotoxicity, viral replication, and Akt1 expression were assessed. TIC tumorigenicity was confirmed and NV1066 efficacy was assessed in vivo. NV1066 infection was highly cytotoxic to both parent HCT8 cells and TICs. In both populations, cell-kill of >80% was achieved within 3 days of infection at a multiplicity of infection (MOI) of 1.0. However, the parent cells required 2-log greater viral replication to achieve the same cytotoxicity. TICs overexpressed Akt1 in vitro and formed flank tumors from as little as 100 cells, growing earlier, faster, larger, and with greater histologic atypia than tumors from parent cells. Treatment of TIC-induced tumors with NV1066 yielded tumor regression and slowed tumor growth. We conclude that colon TICs are selected for by serum-free culture, overexpress Akt1, and are susceptible to oncolytic viral infection.

中文翻译：

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溶瘤性单纯疱疹病毒杀死干细胞样肿瘤引发的结肠癌细胞。

茎样肿瘤起始细胞（TICs）与癌症的进展和复发有关，可以通过球形成和致瘤性分析来鉴定。溶瘤病毒感染，复制并杀死各种癌细胞。在这项研究中，我们寻求TIC易受病毒感染的原理性证明。对HCT8人结肠癌细胞进行无血清培养，以产生TIC肿瘤球。HSV-1亚型NV1066感染了母细胞和TIC。评估细胞毒性，病毒复制和Akt1表达。确认了TIC的致瘤性，并在体内评估了NV1066的功效。NV1066感染对亲本HCT8细胞和TIC均具有高度的细胞毒性。在两个种群中，感染复数（MOI）为1.0时，感染后3天内均达到了> 80％的细胞杀死率。然而，亲本细胞需要2 log更大的病毒复制才能达到相同的细胞毒性。TICs在体外过表达Akt1，由少至100个细胞形成侧翼肿瘤，比亲代细胞的肿瘤更早，更快，更大且组织学上的异型性更高。用NV1066治疗TIC诱导的肿瘤可导致肿瘤消退并减慢肿瘤的生长。我们得出的结论是，结肠TICs是通过无血清培养选择的，过表达Akt1，并且易受溶瘤病毒感染。