細胞核中p-ser-294-FOXO3a表現在乳癌中的角色

Role of nuclear phospho-ser-294-FOXO3a expression in breast cancer

顏良宇(Liang-Yu Yan)

指導教授 ： 侯明鋒

共同指導教授 ： 葉耀宗(Yao-Tsung YEH)

高雄醫學大學/醫學院/醫學研究所碩士班/碩士(2019年)

摘要

根據衛生署統計分析，乳癌為我國婦女發生率第1位之癌症，相較於西方國家，在台灣發病年齡有「早發性」的特徵。因此，探討作用機制、探尋預後因子以及標靶治療為台灣乳癌的重要議題。
FOXO3a是Forkhead box O (FOXO) 轉錄因子的成員，介導人類癌症中廣泛的細胞凋亡、DNA損傷和細胞週期進程。 儘管FOXO3a在某些癌症中經常作為腫瘤抑制作用，但FOXO3a通過與ERK直接相互作用在Ser 294,344和425位點磷酸化後促進細胞增殖和腫瘤發生。 在本篇論文，我們的目的是探討p-Ser-294 FOXO3a在乳癌中細胞內分佈所代表的預後意義。
216名乳癌患者的免疫組織化學結果顯示，細胞核中p-ser-294-FOXO3a (p-FOXO3a) index增加與患者復發呈負相關 (p=0.041)，但與淋巴結轉移呈正相關 (p=0.035)。我們也發現，在細胞核高p-FOXO3a index的患者存活率更高 (p=0.037)。更有趣的是，在細胞核高p-FOXO3a index的患者在使用賀爾蒙治療後 (p=0.05) 以及ER陽性 (p=0.036) 的患者都具有更好的存活率。
FOXO3a的異位過表達抑制MCF-7和HER2 stable clone的生長，但促進SKBR3細胞的增殖，表明HER2相關信號也可能參與調節FOXO3a的活性。另一方面，我們也發現FOXO3a異位過表達增加了乳癌細胞中MMP13的表現。Tamoxifen (Tam) 減少FOXO3a誘導的MMP13表現和p-FOXO3a表現，表明ER和p-FOXO3a可能都參與調節FOXO3a所誘導的MMP13表現。然而，突變型FOXO3a (FOXO3a S294A) 的異位過表達並不改變MMP13增加的情況。結果顯示p-FOXO3a不直接調節MMP13的表現。綜合上述結果，p-FOXO3a不直接調節MMP13的表現而促使乳癌細胞的轉移。未來，我們將進一步探討p-FOXO3a在乳癌轉移中的潛在機制。

關鍵字

乳癌 ； FOXO3a

並列摘要

In Taiwan, according to the statistics of Department of Health, breast cancer has been ranked the first in the incidence of women-specific malignancies. Of note, Taiwanese breast cancer has different oncogenic contents such as earlier onset when compared with western population. Thus, it is a critical issue to explore the underlying mechanisms and to discover the prognostic factors and/or therapeutic targets for Taiwanese breast cancer.
FOXO3a is a member of the Forkhead box O (FOXO) transcription factors and mediates a wide spectrum of apoptosis, DNA damage and cell cycle progression in human cancers. Although FOXO3a frequently acts as a tumor suppressor in certain cancer, FOXO3a promotes cell proliferation and tumorigenesis upon its phosphorylation at Ser 294, 344 and 425 through directly interacting with ERK. Herein, we aim to explore the prognostic significance of subcellular distribution of p-Ser-294-FOXO3a in breast cancer.
Immunohistochemistry results of 216 breast cancer patients showed that increased p-ser-294-FOXO3a (p-FOXO3a) index in the nucleus was inversely correlated to patient's recurrence (p=0.041) but positively correlated with lymph node metastasis (p=0.035). We also found that a better survival rate was shown in patients with high nuclear p-FOXO3a index (p=0.037). More intriguingly, the patients with high nuclear p-FOXO3a index had a better survival rate when they treated with hormone therapy (p=0.05) as well as presented with positive ER status (p=0.036). Ectopic overexpression of FOXO3a inhibited the growth of MCF-7 and HER2 stable clone but promoted proliferation of SKBR3 cells, suggesting that HER2 related signals might also be involved in the regulation of FOXO3a activity. On the other hand, we also found that Ectopic FOXO3a overexpression increased the expression of MMP13 in breast cancer cells. Tamoxifen (Tam) reduced FOXO3a-induced MMP13 expression and p-FOXO3a expression, suggesting that ER and p-FOXO3a might be both involved in the regulation of FOXO3a-induced MMP13 expression. However, ectopic overexpression of S294A-FOXO3a mutant did not alter MMP13 expression. The results showed that p-FOXO3a did not directly regulate the expression of MMP13. Taken together, p-FOXO3a does not directly regulate the expression of MMP13, which promotes the metastasis of breast cancer cells. In the future, we will further explore the potential mechanism of p-FOXO3a in breast cancer metastasis.

並列關鍵字

breast cancer ； FOXO3a

參考文獻

1. Oeffinger, K.C., et al., Breast Cancer Screening for Women at Average Risk: 2015 Guideline Update From the American Cancer Society. Jama, 2015. 314(15): p. 1599-614.

2. DeSantis, C.E., et al., Breast cancer statistics, 2017, racial disparity in mortality by state. CA Cancer J Clin, 2017. 67(6): p. 439-448.

3. Harbeck, N. and M. Gnant, Breast cancer. Lancet, 2017. 389(10074): p. 1134-1150.

4. Valdora, F., et al., Rapid review: radiomics and breast cancer. Breast Cancer Res Treat, 2018. 169(2): p. 217-229.

5. Giovannelli, P., et al., The Androgen Receptor in Breast Cancer. Front Endocrinol (Lausanne), 2018. 9: p. 492.