Ursodeoxycholic acid induces apoptosis in human gastric cancer cells

Abstract

위암은 전세계적으로 흔한 종양이지만 기존의 외과적 수술, 방사선요법 및 화학요법은 치료효율이 제한적이어서 새로운 치료법의 개발이 필요한 상황이다. 저자들은 ursodeoxycholic acid (UDCA)가 위암세포주 SNU-601과 SNU-638에서 주로 apoptosis를 일으키는 것을 알아냈다. UDCA에 의한 apoptosis는 death receptor를 직접 경유하며 mitochondria 경로는 간접적으로 경유하지만 ER 스트레스 경로는 거치지 않는 것으로 확인되었다. UDCA에 의한 apoptosis 유도는 두 세포주 모두에서 lipid raft-ROS-PKC δ-DR5 경로를 통하여 일어나지만 lipid raft/MEK/ERK 경로는 SNU-601 세포에서만 작용됨을 알아냈다. 따라서 UDCA는 위암의 효과적인 치료를 위한 새로운 치료법 개발에 희망적인 항암치료제 또는 항암치료보조제로 사용될 가치가 있는 것으로 판단된다.

Key words: Ursodeoxycholic acid, apoptosis, DR5, lipid raft, ROS, PKC δ, MEK, ERK|Gastric cancer is the major cause of cancer death in the world. Since the efficacy of therapeutic approaches such as surgery, radio- and chemotherapy is limited, the novel chemotherapeutic agents are needed to treat gastric cancer. We showed that ursodeoxycholic acid (UDCA) mainly induced apoptosis in two different human gastric cancer cells SNU-601 and SNU-638 cells. UDCA-induced apoptosis was dependent on caspases-3, -6, -9 and -8 but not caspase-4, indicating that UDCA induced apoptosis through directly death receptor and indirectly mitochondrial pathway but not endoplasmic reticulum stress pathway. UDCA induced expression of DR5 and knock-down of expression of DR5 significantly suppressed UDCA-induced apoptosis. UDCA activated the translocation of protein kinase C delta (PKC δ), and inhibition of PKC δ significantly suppressed UDCA-induced expression of DR5 to trigger apoptosis. Moreover, UDCA stimulated ROS production, and ROS scavengers significantly prevented UDCA-induced expression of DR5 to trigger apoptosis. In addition, NAC blocked UDCA-activated the translocation of PKC δ from cytosol to membrane. Interestingly, lipid raft depleting agent, methyl-β-cyclodextrin (MBCD) completely suppressed ROS production and the translocation of PKC δ from cytosol to membrane as well as expression of DR5 and apoptosis by UDCA in both cancer cell lines. On the other hand, UDCA activated phosphorylation status of MEK/ERK and inhibition of MEK1/2 prevented UDCA-induced expression of DR5 to trigger apoptosis in SNU-601 cells but not in SNU-638 cells. In addition, siRNA ERK1 but not siRNA ERK2 partially prevented UDCA-induced expression of DR5 to trigger apoptosis. Moreover, UDCA-activated phosphorylation status of MEK/ERK was completely blocked by MBCD in SNU-601 cells. Overall, for the first time, our results suggest that UDCA-induced apoptosis is significantly regulated by lipid raft/ROS/PKC δ pathway in both cancer cell lines and partially regulated by lipid raft/MEK/ERK1 pathway in SNU-601 cells. Taken together, UDCA can be a potential chemotherapeutic agent to develop for the new promising strategy to treat gastric cancer at clinical trial in the future.

Key words: Ursodeoxycholic acid, apoptosis, DR5, lipid raft, ROS, PKC δ, MEK, ERK