Department of General Surgery, En Chu Kong Hospital, New Taipei City 237, Taiwan.
Department of Health Care Management, Yuanpei University of Medical Technology, Hsinchu 300, Taiwan.
Cells. 2020 Apr 20;9(4):1020. doi: 10.3390/cells9041020.
With recorded under-performance of current standard therapeutic strategies as highlighted by high rates of post-treatment (resection or local ablation) recurrence, resistance to chemotherapy, poor overall survival, and an increasing global incidence, hepatocellular carcinoma (HCC) constitutes a medical challenge. Accumulating evidence implicates the presence of HCC stem cells (HCC-SCs) in HCC development, drug-resistance, recurrence, and progression. Therefore, treatment strategies targeting both HCC-SCs and non-CSCs are essential.
Recently, there has been an increasing suggestion of MALAT1 oncogenic activity in HCC; however, its role in HCC stemness remains unexplored. Herein, we investigated the probable role of MALAT1 in the SCs-like phenotype of HCC and explored likely molecular mechanisms by which MALAT1 modulates HCC-SCs-like and metastatic phenotypes.
We showed that relative to normal, cirrhotic, or dysplastic liver conditions, MALAT1 was aberrantly expressed in HCC, similar to its overexpression in Huh7, Mahlavu, and SK-Hep1 HCC cells lines, compared to the normal liver cell line THLE-2. We also demonstrated a positive correlation between MALAT1 expression and poor cell differentiation status in HCC using RNAscope. Interestingly, we demonstrated that shRNA-mediated silencing of MALAT1 concomitantly downregulated the expression levels of β-catenin, Stat3, c-Myc, CK19, vimentin, and Twist1 proteins, inhibited HCC oncogenicity, and significantly suppressed the HCC-SCs-related dye-effluxing potential of HCC cells and reduced their ALDH-1 activity, partially due to inhibited MALAT1-β-catenin interaction. Additionally, using TOP/FOP (TCL/LEF-Firefly luciferase) Flash, RT-PCR, and western blot assays, we showed that silencing MALAT1 downregulates β-catenin expression, dysregulates the canonical Wnt signaling pathway, and consequently attenuates HCC tumorsphere formation efficiency, with concurrent reduction in CD133+ and CD90+ HCC cell population, and inhibits tumor growth in SK-Hep1-bearing mice. Taken together, our data indicate that MALAT1/Wnt is a targetable molecular candidate, and the therapeutic targeting of MALAT1/Wnt may constitute a novel promising anticancer strategy for HCC treatment.
由于当前标准治疗策略的表现不佳，如治疗后（切除或局部消融）复发率高、对化疗耐药、总体生存率低以及全球发病率不断上升，肝细胞癌（HCC）构成了一个医学挑战。越来越多的证据表明 HCC 干细胞（HCC-SCs）在 HCC 的发生、耐药、复发和进展中起作用。因此，针对 HCC-SCs 和非 CSCs 的治疗策略是必不可少的。
最近，越来越多的证据表明 MALAT1 在 HCC 中具有致癌活性；然而，其在 HCC 干性中的作用仍未得到探索。在此，我们研究了 MALAT1 在 HCC 样干细胞表型中的可能作用，并探讨了 MALAT1 调节 HCC-SCs 样和转移表型的可能分子机制。
与正常、肝硬化或异型增生的肝脏相比，MALAT1 在 HCC 中异常表达，与 Huh7、Mahlavu 和 SK-Hep1 HCC 细胞系相比，正常肝细胞系 THLE-2 中 MALAT1 的表达上调。我们还使用 RNAscope 证明了 MALAT1 表达与 HCC 中细胞分化状态不良呈正相关。有趣的是，我们证明了 shRNA 介导的 MALAT1 沉默同时下调了 β-catenin、Stat3、c-Myc、CK19、波形蛋白和 Twist1 蛋白的表达水平，抑制了 HCC 的致癌性，并显著抑制了 HCC 细胞的 HCC-SCs 相关染料外排潜能，降低了它们的 ALDH-1 活性，部分原因是抑制了 MALAT1-β-catenin 相互作用。此外，我们使用 TOP/FOP（TCL/LEF-Firefly 荧光素酶）Flash、RT-PCR 和 Western blot 分析表明，沉默 MALAT1 下调了 β-catenin 的表达，使经典 Wnt 信号通路失调，从而降低 HCC 肿瘤球形成效率，同时减少了 CD133+和 CD90+的 HCC 细胞群体，并抑制了 SK-Hep1 荷瘤小鼠的肿瘤生长。
综上所述，我们的数据表明 MALAT1/Wnt 是一个可靶向的分子候选物，靶向 MALAT1/Wnt 的治疗可能构成 HCC 治疗的一种新的有前途的抗癌策略。
