Reversible cellular senescence was demonstrated previously to constitute colon cancer cell response to methotrexate. The current study presents a comparison of two senescent states of colon cancer cells, arrested and reversing, resulting from respectively, 120 h exposure to the drug, and 48 h exposure followed by 96 h regrowth in drug-free media. The upregulation of immunoproteasome subunit-coding genes and the increase in human leukocyte antigen HLA-A/B/C membrane level indicated MHC-I-restricted antigen presentation as common to both senescent states. Nuclear factor NF-κB p65 level decreased and activating protein AP-1: c-Jun, Fra2 and JunB nuclear levels increased in both senescent cell populations. Notably, the increase in AP-1- dependent transcription occurred after 48 h exposure to methotrexate. β-catenin nuclear level increased after 48 h exposure to the drug and remained as such only in senescence-arrested cells. β-catenin level was found uncoupled from the protein phosphorylation status indicating the deregulation of β-catenin signaling in colon cancer cells employed in the study. These findings carry implications for both, a general mechanism of senescence establishment and putative advantages for colon cancer treatment.

先前已证明可逆的细胞衰老构成结肠癌细胞对甲氨蝶呤的反应。目前的研究比较了结肠癌细胞的两种衰老状态，即停滞和逆转，分别由暴露于药物 120 小时和暴露 48 小时，然后在无药物培养基中再生 96 小时引起。免疫蛋白酶体亚基编码基因的上调和人类白细胞抗原 HLA-A/B/C 膜水平的增加表明 MHC-I 限制性抗原呈递对于两种衰老状态都是常见的。在两个衰老细胞群中，核因子 NF-κB p65 水平降低，激活蛋白 AP-1：c-Jun、Fra2 和 JunB 核水平增加。值得注意的是，AP-1 依赖性转录的增加发生在暴露于甲氨蝶呤 48 小时后。β-连环蛋白核水平在暴露于药物 48 小时后增加，并且仅在衰老停滞细胞中保持不变。发现β-连环蛋白水平与蛋白质磷酸化状态无关，表明该研究中使用的结肠癌细胞中β-连环蛋白信号传导的失调。这些发现对两者都有影响，即衰老建立的一般机制和结肠癌治疗的假定优势。