Globo-H 結合對硝基苯作為抗癌症疫苗的研究

Abstract

大部分癌症細胞表面會表現多量的特定醣抗原，Globo H (Fucα1→2Galβ1→ 3GalNAcβ1→ 3Galα1→4Galβ1→ 4Glc)六碳醣是其中一種，它高度表現在乳癌、前列腺癌、卵巢癌、胰腺癌、大腸直腸癌及肺癌之細胞表面。Danishefsky的研究發現Globo H接上KLH蛋白當作疫苗可以產上抗體專一性的針對癌細胞，另外Schultz證明將蛋白質之某一個酪氨酸(Tyr)置換成對硝基苯丙氨酸(pNO2Phe)產生高表現量的抗體，且此抗體亦可針對未突變的蛋白。因此本篇的目標是結合Globo H及pNO2Phe為特別的醣抗原，接上牛血清白蛋白(BSA)當作抗癌疫苗(GHN-BSA)，和Globo H直接接上牛血清蛋白結合的抗癌疫苗(GH-BSA)作比較，預期GHN-BSA可以產生高表現量抗體辨認Globo H醣抗原。由動物實驗的結果顯示GHN-BSA產生高表現量的抗體，可惜此沒有辨認Globo H醣抗原，而是辨認pNO2Phe，而由GH-BSA可以產生專一性辨認Globo H的抗體。我們推論因對硝基苯是強烈的免疫抗原，而設計之疫苗上Globo H及pNO2Phe在GHN-BSA占有相同的比例，導致結果不如預期，假如修改其之間的比例或許可以產生高表現的抗體專一性辨認Globo H醣抗原，下一代的GHN-BSA疫苗使用不同的連結方式來提升Globo H和pNO2Phe的比例至5.14/1.36，且動物實驗正要進行，希望可以得到預期的效果。

Most of the cancer cells expressed large amounts of carbohydrate antigens on the cell surface. For example, an antigenic hexasaccharide, Globo H (Fucα1→2Galβ1→ 3GalNAcβ1 → 3Galα1→4Galβ1→4Glc), is overexpressed in surfaces of many human cancers, including breast, prostate, ovary, pancreas, colon and lung cancers. It was previously demonstrated that BSA-conjugated Globo H(GH-BSA) adjuvanted with α-GalCer can induce Globo H-specific antibodies. Another study led by Schultz showed that the incorporation of a p-nitrophenylalanine onto TNF can induce a potent antibody response in mice. Herein, we further linked Globo H to p-nitrophenyl group and the resulting unit was conjugated to BSA (GHN-BSA) and explored its immune-eliciting ability as a cancer vaccine. Animal experiments showed that antibodies induced by GHN-BSA vaccine recognized the p-nitrophenyl group but not Globo H carbohydrate antigen. On the other hand, antibodies induced by GH-BSA vaccine recognize Globo H and analogues. We hypothesized that since the p-nitrophenyl group is a strong immunogen and Globo H is a weak one, the same proportion of Globo H to pNO2Phe in the vaccine candidate GHN-BSA would lead to much more antibodies for pNO2Phe. Hence, a new generation of GHN-BSA vaccine with ratio of Globo H over pNO2Phe is 3.78 was synthesized and immunization experiments are ongoing. We wished that raising the ratio of Globo H over pNO2Phe may be able to enhance antibodies specifically to recognize Globo H antigen.