新抗微管藥物LTP-1在人類胰臟癌細胞之作用機轉探討

Abstract

胰臟癌的癌症死亡率排名在台灣為第九位，由於此癌症不容易在早期被發現，所以患者的存活率極低。本研究的目的是探討化學合成新藥物LTP-1對於人類胰臟癌細胞的藥理機轉。首先，在SRB和MTT實驗中發現LTP-1能有效抑制胰臟癌細胞的生長與存活；接著，我們利用PI染色合併流式細胞儀分析發現LTP-1在短時間處理能讓胰臟癌細胞停滯在G2/M期；除此之外，LTP-1也會抑制微管聚合，並使M期指標蛋白MPM2和Histone-3 Ser10磷酸化增加；同時，我們也發現LTP-1在胰臟癌細胞中會抑制STAT3的磷酸化，不過這與LTP-1促使細胞週期停在G2/M期無關。另外，LTP-1也會活化ERK，但給予ERK抑制劑PD98059並不會抑制LTP-1所造成的G2/M期停滯。而長期給予LTP-1則會讓細胞形成多倍體及增加subG1的細胞數，也會導致PARP cleavage並活化caspase-3、-7、-8、-9。最後，在小鼠腫瘤異體移植實驗中證實LTP-1能抑制人類胰臟癌細胞AsPC-1的生長。綜合以上結果，LTP-1能改變微管蛋白的動態，進而使細胞週期停滯在G2/M期，最終將導致細胞形成多倍體並經由caspase 活化來造成細胞凋亡，所以LTP-1具有潛力發展成為新的抗癌藥物。

Pancreatic cancer is the ninth cause of cancer deaths in Taiwan. Pancreatic cancer patients are always diagnosed at an advanced stage resulting in poor survival rates. The purpose of this study is to determine the mechanism of action of a new synthetic compound LTP-1 on human pancreatic cancer in vitro and in vivo. The study demonstrated that LTP-1 inhibited cell growth and viability in the AsPC1 and PANC-1 human pancreatic cancer cells. Using flow cytometry analysis, we found that short-term treatment of LTP-1 could significantly induce G2/M arrest in the cell cycle progression. The data showed that LTP-1 could disrupt microtubule dynamics and induce phosphorylation of two mitotic markers, MPM2 and Histone-3 Ser10, in a concentration-dependent manner. Furthermore, LTP-1 inhibited STAT3 tyrosine phosphorylation and induced ERK activation; however, both of which did not contribute to G2/M arrest. Long-term treatment of LTP-1 induced polyploidy and triggered them to undergo apoptosis through catalytic cleavage of caspase-3, -7, -8, -9, and poly (ADP-ribose) polymerase (PARP). Finally, we used an in vivo xenograft mouse model to demonstrate that LTP-1 suppressed pancreatic adenocarcinoma AsPC-1 growth. In summary, the results suggest that LTP-1 can change microtubule dynamics, and leading to G2/M arrest of the cell cycle which ultimately causes polyploidy and apoptosis through the intrinsic and extrinsic apoptotic pathways. The study provides evidence that LTP-1 is a potential anticancer agent for further development.