The property of drug-resistance may attenuate clinical therapy in cancer cells, such as chemoresistance to gefitinib in colon cancer cells. In previous studies, overexpression of PD-L1 causes proliferation and metastasis in cancer cells; therefore, the PD-L1 pathway allows tumor cells to exert an adaptive resistance mechanism in vivo. Nano-diamino-tetrac (NDAT) has been shown to enhance the anti-proliferative effect induced by first-line chemotherapy in various types of cancer, including colorectal cancer (CRC). In this work, we attempted to explore whether NDAT could enhance the anti-proliferative effect of gefitinib in CRC and clarified the mechanism of their interaction. The MTT assay was utilized to detect a reduction in cell proliferation in four primary culture tumor cells treated with gefitinib or NDAT. The gene expression of PD-L1 and other tumor growth-related molecules were quantified by quantitative polymerase chain reaction (qPCR). Furthermore, the identification of PI3K and PD-L1 in treated CRC cells were detected by western blotting analysis. PD-L1 presentation in HCT116 xenograft tumors was characterized by specialized immunohistochemistry (IHC) and the hematoxylin and eosin stain (H&E stain). The correlations between the change in PD-L1 expression and tumorigenic characteristics were also analyzed. (3) The PD-L1 was highly expressed in Colo_160224 rather than in the other three primary CRC cells and HCT-116 cells. Moreover, the PD-L1 expression was decreased by gefitinib (1 µM and 10 µM) in two cells (Colo_150624 and 160426), but 10 µM gefitinib stimulated PD-L1 expression in gefitinib-resistant primary CRC Colo_160224 cells. Inactivated PI3K reduced PD-L1 expression and proliferation in CRC Colo_160224 cells. Gefitinib didn’t inhibit PD-L1 expression and PI3K activation in gefitinib-resistant Colo_160224 cells. However, NDAT inhibited PI3K activation as well as PD-L1 accumulation in gefitinib-resistant Colo_160224 cells. The combined treatment of NDAT and gefitinib inhibited pPI3K and PD-L1 expression and cell proliferation. Additionally, NDAT reduced PD-L1 accumulation and tumor growth in the HCT116 (K-RAS mutant) xenograft experiment. (4) Gefitinib might suppress PD-L1 expression but did not inhibit proliferation through PI3K in gefitinib-resistant primary CRC cells. However, NDAT not only down-regulated PD-L1 expression via blocking PI3K activation but also inhibited cell proliferation in gefitinib-resistant CRCs.

中文翻译：

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NDAT靶向PI3K介导的PD-L1上调，以减少耐吉非替尼的结直肠癌的增殖。

耐药性可能会削弱癌细胞的临床治疗，例如结肠癌细胞对吉非替尼的化学耐药性。在先前的研究中，PD-L1的过度表达会导致癌细胞的增殖和转移。因此，PD-L1途径允许肿瘤细胞在体内发挥适应性耐药机制。纳米二氨基丁四酸（NDAT）已显示出可增强一线化疗在各种类型的癌症（包括结直肠癌（CRC））中诱导的抗增殖作用。在这项工作中，我们试图探讨NDAT是否可以增强吉非替尼在CRC中的抗增殖作用，并阐明其相互作用的机制。使用MTT测定法检测用吉非替尼或NDAT处理的四种原代培养肿瘤细胞中细胞增殖的减少。的基因表达通过定量聚合酶链反应（qPCR）对PD-L1和其他与肿瘤生长相关的分子进行定量。此外，通过蛋白质印迹分析检测了处理过的CRC细胞中PI3K和PD-L1的鉴定。HCT116异种移植肿瘤中的PD-L1表现通过专门的免疫组织化学（IHC）以及苏木精和曙红染色（H＆E染色）进行了表征。还分析了PD-L1表达的变化与致瘤特性之间的相关性。（3）的PD-L1在Colo_160224高度表达，而不是在其他三个主CRC细胞和HCT-116细胞。此外，吉非替尼（1 µM和10 µM）在两个细胞（Colo_150624和160426）中降低了PD-L1的表达，但吉非替尼刺激了10 µMPD-L1在耐吉非替尼的原代CRC Colo_160224细胞中的表达。灭活的PI3K降低了CRC Colo_160224细胞中PD-L1的表达和增殖。吉非替尼不抑制耐吉非替尼的Colo_160224细胞中PD-L1表达和PI3K活化。但是，NDAT在耐吉非替尼的Colo_160224细胞中抑制了PI3K激活以及PD-L1的积累。NDAT和吉非替尼的联合治疗抑制pPI3K和PD-L1的表达以及细胞增殖。此外，在HCT116（K-RAS突变体）异种移植实验中，NDAT减少了PD-L1的积累和肿瘤的生长。（4）吉非替尼可能抑制PD-L1在耐吉非替尼的原代CRC细胞中表达，但未通过PI3K抑制增殖。但是，NDAT不仅通过阻断PI3K激活来下调PD-L1表达，而且还抑制了对吉非替尼耐药的CRC细胞的增殖。