Department of Biopharmaceutics, School of Pharmacy, Tokyo University of Pharmacy and Life Sciences (K.M., H.Ki, H.Ko, A.S., K.H., and K.I.) and Faculty of Pharmacy, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University (Y.S.).
Department of Biopharmaceutics, School of Pharmacy, Tokyo University of Pharmacy and Life Sciences (K.M., H.Ki, H.Ko, A.S., K.H., and K.I.) and Faculty of Pharmacy, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University (Y.S.)
Mol Pharmacol. 2023 Mar;103(3):166-175. doi: 10.1124/molpharm.122.000597. Epub 2022 Dec 5.
Mucin 1 (MUC1) is aberrantly expressed in various cancers and implicated in cancer progression and chemoresistance. Although the -terminal cytoplasmic tail of MUC1 is involved in signal transduction, promoting chemoresistance, the role of the extracellular MUC1 domain [-terminal glycosylated domain (NG)-MUC1] remains unclear. In this study, we generated stable MCF7 cell lines expressing MUC1 and cytoplasmic tail-deficient MUC1 (MUC1ΔCT) and show that NG-MUC1 is involved in drug resistance by modulating the transmembrane permeation of various compounds without cytoplasmic tail signaling. Heterologous expression of MUC1ΔCT increased cell survival in treating anticancer drugs (such as 5-fluorouracil, cisplatin, doxorubicin, and paclitaxel), in particular by causing an approximately 150-fold increase in the IC of paclitaxel, a lipophilic drug, compared with the control [5-fluorouracil (7-fold), cisplatin (3-fold), and doxorubicin (18-fold)]. The uptake studies revealed that accumulations of paclitaxel and Hoechst 33342, a membrane-permeable nuclear staining dye, were reduced to 51% and 45%, respectively, in cells expressing MUC1ΔCT via ABCB1/P-gp-independent mechanisms. Such alterations in chemoresistance and cellular accumulation were not observed in MUC13-expressing cells. Furthermore, we found that MUC1 and MUC1ΔCT increased the cell-adhered water volume by 2.6- and 2.7-fold, respectively, suggesting the presence of a water layer on the cell surface created by NG-MUC1. Taken together, these results suggest that NG-MUC1 acts as a hydrophilic barrier element against anticancer drugs and contributes to chemoresistance by limiting the membrane permeation of lipophilic drugs. Our findings could help better the understanding of the molecular basis of drug resistance in cancer chemotherapy. SIGNIFICANCE STATEMENT: Membrane-bound mucin (MUC1), aberrantly expressed in various cancers, is implicated in cancer progression and chemoresistance. Although the MUC1 cytoplasmic tail is involved in proliferation-promoting signal transduction thereby leading to chemoresistance, the significance of the extracellular domain remains unclear. This study clarifies the role of the glycosylated extracellular domain as a hydrophilic barrier element to limit the cellular uptake of lipophilic anticancer drugs. These findings could help better the understanding of the molecular basis of MUC1 and drug resistance in cancer chemotherapy.
黏蛋白 1（MUC1）在各种癌症中异常表达，与癌症进展和化疗耐药有关。尽管 MUC1 的胞质尾端参与信号转导，促进化疗耐药，但细胞外 MUC1 结构域[-末端糖基化结构域（NG）-MUC1]的作用仍不清楚。在这项研究中，我们生成了稳定表达 MUC1 和缺乏胞质尾端的 MUC1（MUC1ΔCT）的 MCF7 细胞系，并表明 NG-MUC1 通过调节各种化合物的跨膜通透性而参与耐药性，而无需胞质尾端信号。MUC1ΔCT 的异源表达增加了细胞对抗癌药物（如 5-氟尿嘧啶、顺铂、阿霉素和紫杉醇）的存活能力，特别是与对照组相比，紫杉醇（亲脂性药物）的 IC 增加了约 150 倍[5-氟尿嘧啶（7 倍），顺铂（3 倍）和阿霉素（18 倍）]。摄取研究表明，通过 ABCB1/P-gp 非依赖性机制，表达 MUC1ΔCT 的细胞中紫杉醇和 Hoechst 33342（一种膜通透性核染色染料）的积累分别减少到 51%和 45%。在表达 MUC13 的细胞中未观察到这种化疗耐药性和细胞内积累的改变。此外，我们发现 MUC1 和 MUC1ΔCT 分别使细胞粘附水体积增加了 2.6 倍和 2.7 倍，这表明 NG-MUC1 在细胞表面形成了一层亲水层。综上所述，这些结果表明 NG-MUC1 作为一种亲水屏障元素对抗癌药物起作用，并通过限制亲脂性药物的膜通透性来促进化疗耐药性。我们的发现可以帮助更好地理解癌症化疗中药物耐药性的分子基础。
