Leung Euphemia Y, Askarian-Amiri Marjan E, Sarkar Debina, Ferraro-Peyret Carole, Joseph Wayne R, Finlay Graeme J, Baguley Bruce C
Auckland Cancer Society Research Centre, University of Auckland, Auckland, New Zealand.
Molecular Medicine and Pathology Department, University of Auckland, Auckland, New Zealand.
Front Oncol. 2017 Sep 4;7:184. doi: 10.3389/fonc.2017.00184. eCollection 2017.
Endocrine therapy of breast cancer, which either deprives cancer tissue of estrogen or prevents estrogen pathway signaling, is the most common treatment after surgery and radiotherapy. We have previously shown for the estrogen-responsive MCF-7 cell line that exposure to tamoxifen, or deprivation of estrogen, leads initially to inhibition of cell proliferation, followed after several months by the emergence of resistant sub-lines that are phenotypically different from the parental line. We examined the early responses of MCF-7 cells following either exposure to 4-hydroxytamoxifen or deprivation of estrogen for periods of 2 days-4 weeks.
Endocrine-sensitive or -resistant breast cancer cell lines were used to examine the expression of the stem cell gene , and the Wnt effector genes and using quantitative PCR analysis. Breast cancer cell lines were used to assess the anti-proliferative effects (as determined by IC values) of Wnt pathway inhibitors LGK974 and IWP-2.
Hormone therapy led to time-dependent increases of up to 10-fold in expression, up to threefold in expression of the Wnt target genes and , and variable changes in and expression. The cells also showed increased mammosphere formation and increased CD24 surface protein expression. Some but not all hormone-resistant MCF-7 sub-lines, emerging after long-term hormonal stress, showed up to 50-fold increases in expression and smaller increases in and expression. However, the increase in Wnt target gene expression was not accompanied by an increase in sensitivity to Wnt pathway inhibitors LGK974 and IWP-2. A general trend of lower IC values was observed in 3-dimensional spheroid culture conditions (which allowed enrichment of cells with cancer stem cell phenotype) relative to monolayer cultures. The endocrine-resistant cell lines showed no significant increase in sensitivity to Wnt inhibitors.
Hormone treatment of cultured MCF-7 cells leads within 2 days to increased expression of components of the and Wnt pathways and to increased potential for mammosphere formation. We suggest that these responses are indicative of early adaptation to endocrine stress with features of stem cell character and that this facilitates the survival of emerging hormone-resistant cell populations.
乳腺癌内分泌治疗是手术和放疗后最常见的治疗方法，该治疗通过剥夺癌组织的雌激素或阻止雌激素信号通路发挥作用。我们之前对雌激素反应性MCF-7细胞系的研究表明，用他莫昔芬处理或剥夺雌激素，最初会抑制细胞增殖，但几个月后会出现与亲代细胞系表型不同的耐药亚系。我们研究了MCF-7细胞在暴露于4-羟基他莫昔芬或剥夺雌激素2天至4周后的早期反应。
使用内分泌敏感或耐药的乳腺癌细胞系，通过定量PCR分析检测干细胞基因、Wnt效应基因和的表达。使用乳腺癌细胞系评估Wnt通路抑制剂LGK974和IWP-2的抗增殖作用（通过IC值确定）。
激素治疗导致表达增加高达10倍，Wnt靶基因和的表达增加高达3倍，以及和表达的变化不定。细胞还表现出乳腺球形成增加和CD24表面蛋白表达增加。长期激素应激后出现的部分但并非所有激素耐药MCF-7亚系，的表达增加高达50倍，和的表达增加幅度较小。然而，Wnt靶基因表达的增加并未伴随着对Wnt通路抑制剂LGK974和IWP-2敏感性的增加。相对于单层培养，在三维球体培养条件下（可富集具有癌干细胞表型的细胞）观察到IC值普遍较低的趋势。内分泌耐药细胞系对Wnt抑制剂的敏感性未显著增加。
对培养的MCF-7细胞进行激素治疗在2天内导致和Wnt通路成分的表达增加以及乳腺球形成潜力增加。我们认为这些反应表明细胞早期适应内分泌应激并具有干细胞特征，这有利于新出现的激素耐药细胞群体的存活。
