癌症幹細胞是一群特別的癌細胞，負責自我複製和促進腫瘤細胞在癌組織中分化與生長的關鍵。有許多證據顯示癌症幹細胞存在於不同種類的癌症中，並和癌症增生、轉移及癌症復發相關。因此， 癌症幹細胞開始成為癌症治療及早期診斷研究中標的細胞。在最近這十年，從不同癌細胞中發現一些癌症幹細胞標記，但這些標記都不能夠有效的將癌症幹細胞從癌細胞有效純化出來。

本篇初期的研究中發現globo-series醣種類的階段特異性胚胎抗原-3 (stage-specific embryonic antigen-3, SSEA-3)、階段特異性胚胎抗原-4 (SSEA-4)和globo-H會特定地表現在分別是由CD44/CD24和ESA/PROCR標記系統篩選出來的乳癌幹細胞。為了拿到高純度的癌症幹細胞，本篇研究發現在體外測試以及動物實驗中，由CD44+CD24-/loSSEA-3+或ESAhiPROCRhiSSEA-3+標記篩選出來的乳癌幹細胞具有高致腫瘤性。和由CD44/CD24和ESA/PROCR標記篩選的乳癌幹細胞相比，將10個由CD44+CD24-/loSSEA-3+標記篩選出來的癌症幹細胞打進老鼠乳腺內可以形成腫瘤，然而由CD44+CD24-/lo標記篩選的癌症幹細胞，需要大於100個癌症幹細胞才可在老鼠乳腺內形成腫瘤。在細胞實驗，減弱 b-1,3半乳糖轉移酶5 (b3GalT5) 的基因表現，可以抑制SSEA-3的表現在合成globo-series的路徑，並導致癌細胞表面標記的改變。由其他的幹細胞包括胚胎幹細胞以胚胎幹細胞 (ESCs, iPSCs)、正常細胞和癌細胞分析SSEA-3、SSEA-4和globo H的表現，進一步支持globo系列醣脂在癌症專一性的發現。

因為在癌細胞中，b3GalT5轉移酶基因的減弱會導致細胞凋亡和細胞死亡，本篇研究提供針對globo-series醣為主的癌症治療和末期乳癌疫苗臨床試驗可靠的證據。

It is proposed that cancer stem cells (CSCs) are special cancer cells responsible for the self-renewal and differentiation in the heterogeneous cancer tissues for supporting tumor hierarchy. There are numerous evidences showing the existence of CSCs in different cancer types. At the same time, CSCs is closely related to cancer progression, as well as the problems in the current cancer therapies such as metastasis and cancer relapse. Therefore, it has stimulated interests in developing new cancer therapies and early diagnosis targeted on CSCs. In order to enrich CSCs for the further studies, many CSC markers were idenified in this decade. However, these marker sets are often not selective enough to enrich such unique cell population. In this research, therefore, using globo-series epitopes, which is associated with embryogenesis and cancers, as the additional marker for enrichment of breast cancer stem cells (BCSCs) were investigated.

At the beginning of the research, it was found that globo-series epitopes stage-specific embryonic antigen-3 (SSEA-3), stage-specific embryonic antigen-4 (SSEA-4) and globo-H were significantly expressed in BCSCs identified with marker systems CD44/CD24 and ESA/PROCR. This study was also illustrated that BCSCs isolated with CD44+CD24-/loSSEA-3+ or ESAhiPROCRhiSSEA-3+ markers had higher tumorigenicity than those with conventional markers in vitro and in vivo. As few as 10 cells with CD44+CD24-/loSSEA-3+ formed tumor in mice, compared to more than 100 cells with CD44+CD24-/lo. Suppression of SSEA-3 by knockdown of the gene encoding b-1,3-galactosyltransferase 5 (b3GalT5) in the globo-series pathway induced the changes of surface markers on cancer cells. Additionally, the overexpression of b3GalT5 enhanced the percentage of cells carrying SSEA-3, and CD44+CD24-/lo. This finding was further supported by the analysis of SSEA-3 and the two related globo-series epitopes SSEA4 and globo-H in stem cells (ESCs and iPSCs), normal and cancer cells.

In addition of the apoptosis and cell death in knockdown b3GalT5 in cancer culture but not in normal one, this study gives solid evidence on the potential cancer therapy targeting the globo-series glycans and the late-stage clinical trials of a breast cancer vaccine.

Sarah K.C. Cheung*, P-K. Chuang*, H-W. Huang, Wendy W. Hwang-Verslues, Candy HH. Cho, W-B. Yang, C-N. Shen, M. Hsiao, T-L. Hsu, C-F. Chang, C-H. Wong. (2015) Stage-Specific Embryonic Antigen-3 (SSEA3) and β3GALT5 are Cancer Specific and are Significant Markers for Breast Cancer Stem Cells, PNAS (published ahead of print December 17, 2015)

Y-L. Huang*, J-T. Hung*, Sarah K.C. Cheung*, H-Y. Lee, K-C. Chu, S-T. Li, Y-C. Lin, C-T. Ren, T-J. R. Cheng, T-L. Hsu, Alice L. Yu, C-Y. Wu & C-H. Wong (2013) Carbohydrate-based vaccines with a glycolipid adjuvant for breast cancer. PNAS, 110 (7):2517-2522