마우스 소장 crypt cell에서 방사선 조사에 의해 유도된 apoptosis의 조절

박상준(Sang-Joon Park),정규식(Kyu-Shik Jeong),김태환(Tae-Hwan Kim),임윤규(Yoon-Kyu Lim),박현정(Hyun-Jeong Park),Pham Duc Chuong,지영흔(Young-Heun Jee) 한국실험동물학회 2004 Laboratory Animal Research Vol.20 No.3

Apoptosis에서의 p53 단백질의 관련성에 관해서는 많은 세포들에서 잘 알려져 있다. 그러나 생체내에서 방사선에 의한 apoptosis를 유도하는 기전과 p53의 관계에 대해서는 명확하지 않다. 본 연구에서는 방사선을 조사한 mouse 소장의 crypt cell에서 선량의 증가에 따른 apoptosis의 양상과 이에 따른 apoptosis 기전을 밝히고자 하였다. 소장 crypt cell에서의 유도된 apoptosis의 빈도는 방사선 조사 후 시간의 경과와 선량의 증가에 의존적이었다. 소장 crypt cell에서의 apoptotic cell의 수는 방사선 조사 후 4-6시 간에 최고치를 나타내었고, 24-48시간 후에는 점차적으로 감소하여 72시간 후에는 현저히 감소되었다. 또한 방사선의 선량의 증가에 따라 소장 crypt cell에서의 apoptotic cell의 수가 현저히 증가하였으며, Western blot analysis에서는 apoptosis의 빈도와 비례하여 선량의 증가에 따른 p53의 발현의 증가를 관찰할 수 있었다. 이상의 결과로부터 생체내에서 방사선에 의해 소장 crypt cell에서 유도된 apoptosis는 p53의 발현과 밀접한 관련이 있음을 알 수 있었다. The involvement of the p53 gene in apoptosis of many cell types is well established. However, little information is available on the relationship between p53 status and their ability to undergo apoptosis following exposure to y-radiation in vivo. The aim of this study was to characterize the apoptotic pathway by γ-radiation in mouse intestinal crypt cells. After ⁶⁰Co γ-ray irradiation, the apoptosis in crypt cells showed a time- and dose-dependent increase. The apoptosis in crypt cells was maximal at 4 and 6hours after irradiation, showed a gradual decline at 24 hours and 48 hours, and was almost absent by 72hours. In addition, the number of apoptotic cells increased sharply with increasing dose of ⁶⁰Co γ-ray. In Western blot analysis, the apoptosis was confirmed to be dependent on p53 function after ⁶⁰Co γ-ray irradiation. In parallel with frequency of apoptosis in crypt cells, p53 expression showed the increased dose-dependent response in intestinal crypt cells. There was a significant correlation between the frequency of apoptosis and the increase of p53 expression in crypt cells. These findings suggest that ⁶⁰Co γ-ray-induced apoptosis in mouse intestinal crypt cells is related to the increase in functional p53 proteins to a level sufficient to initiate apoptosis.

Sanguinarine에 의한 Hep3B 인체 간암세포의 apoptosis 유도에 관한 연구

한민호(Min Ho Han),최성현(Sung Hyun Choi),홍수현(Su Hyun Hong),박동일(Dong Il Park),최영현(Yung Hyun Choi) 한국생명과학회 2017 생명과학회지 Vol.27 No.11

Sanguinarine은 다양한 목적으로 사용되고 있는 Sanguinaria canadensis L.의 뿌리에서 유래된 benzophenanthridine alkaloid 계열 물질중의 하나이다. 그동안 sanguinarine의 다양한 약리학적인 효능이 알려져 왔고, 항암활성에 대한 연구도 여러 암세포들을 대상으로 수행되어 왔다. 그러나 sanguinarine에 의한 암세포의 apoptosis 유도에 대한 현상은 여전히 많은 부분에서 연구의 대상으로 남아 있다. 본 연구는 Hep3B 인체 간암세포를 대상으로 sanguinarine의 항암활성에 대한 추가적인 자료를 제시하기 위하여 수행되었다. 본 논문의 결과에 의하면, sanguinarine은 처리 농도 의존적으로 Hep3B 세포의 증식을 억제하였으며, 이는 apoptosis 유도와 연관성이 있었다. Sanguinarine은 두 가지 apoptosis 경로인 extrinsic 및 intrinsic 경로의 개시 initiator caspase인 caspase-8 및 caspase-9 뿐만 아니라 대표적인 effector caspase인 caspase-3의 활성을 증가시켰고, caspase-3의 기질인 PARP의 분절을 유발하였다. 아울러 sanguinarine은 DR-related 유전자들의 발현을 부분적으로 증가시켰으며, Bcl-2 family에 속하는 pro-apoptotic Bax의 발현을 증가시킨 반면, anti-apoptotic Bcl-2의 발현은 억제시켰다. 또한 sanguinarine은 Bid의 truncation을 촉진하였고, MMP의 소실에 따른 cytochrome c를 미토콘드리아에서 세포질로의 이동을 증가시켰다. 그리고 sanguinarine에 의한 apoptosis 유도 및 세포 증식율 억제 현상이 caspase의 활성을 인위적으로 억제하였을 경우, 모두 사라졌다. 따라서 sanguinarine에 의하여 유도하는 Hep3B 세포의 apoptosis 유발에는 caspase 의존적으로 extrinsic 및 intrinsic 경로가 모두 관여하고 있음을 알 수 있었다. Sanguinarine is a benzophenanthridine alkaloid derived from the roots of Sanguinaria canadensis L., which is used for the purpose of treating various diseases. Although studies of anticancer activities have been performed using various cancer cell lines, the phenomenon of inducing apoptosis in cancer cells by using sanguinarine requires more research. Therefore, this study investigated the anti-cancer activities and related mechanisms of sanguinarine used with Hep3B human hepatocellular carcinoma cells in terms of the regulation of apoptosis. Sanguinarine inhibited the proliferation of Hep3B cells in a concentration-dependent manner, which was associated with the induction of apoptosis. Sanguinarine also increased the activity of caspase-3, which is a typical effector caspase, and the activities of caspase-8 and caspase-9, which are key when initiating extrinsic and intrinsic apoptosis pathways, respectively. In addition, sanguinarine increased the expression of death receptor-related genes and pro-apoptotic BAX, which belongs to the Bcl-2 family, while suppressing the expression of anti-apoptotic Bcl-2. Sanguinarine promoted the truncation of Bid and enhanced the release of cytochrome c from the mitochondria to the cytoplasm due to a loss of mitochondrial membrane potential. Furthermore, the reduction of a survival rate that was induced by sanguinarine and the induction of apoptosis disappeared with the inhibition of artificial caspase activity. Therefore, the results of the study indicated that sanguinarine-induced apoptosis in Hep3B cells involves both extrinsic and intrinsic pathways; such apoptosis is a caspase-dependent phenomenon.

인체 방광암 T24 세포에서 감초(Glycyrrhizae radix) 열수추출물에 의한 apoptosis 유도

이기원,김정일,이승영,최경민,오영택,정진우 한국자원식물학회 2019 한국자원식물학회지 Vol.32 No.4

Glycyrrhizae radix is one of the most frequently prescribed ingredients in Oriental medicine, and Glycyrrhizae radix extract has been shown to exert anti-cancer effects. However, the cellular and molecular mechanisms of programed cell death (apoptosis) by Glycyrrhizae radix are poorly defined. In the present study, it was examined the molecular mechanisms of apoptosis by water extracts of Glycyrrhizae radix (GRW) in human bladder T24 cancer cells. It was found that GRW could inhibit the cell growth of T24 cells in a concentration-dependent manner, which was associated with the induction of apoptotic cell death, as evidenced by the formation of apoptotic bodies, DNA fragmentation and increased populations of annexin-V positive cells. The induction of apoptotic cell death by GRW was connected with an up-regulation of pro-apoptotic Bax protein expression and down-regulation of anti-apoptotic proteins (Bcl-2 and Bcl-xL), and inhibition of apoptosis family proteins (XIAP, cIAP-1 and cIAP-2). In addition, apoptosis-inducing concentrations of GRW induced the activation of caspase-9, an initiator caspase of the mitochondrial-mediated intrinsic pathway, and caspase-3, accompanied by proteolytic degradation of PARP. GRW also induced apoptosis via a death receptor-mediated extrinsic pathway by caspase-8 activation, resulting in the down-regulation of total Bid and suggesting the existence of cross-talk between the extrinsic and intrinsic pathways. Taken together, the present results suggest that GRW may be a potential chemotherapeutic agent for the control of human bladder cancer cells. 본 연구에서는 다양한 약리학적 활성을 가지는 것으로 알려진 감초 열수추출물(GRW)의 항암효능을 알아보기 위하여 인체방광암 T24 세포에서 생존율 및 증식억제에 미치는 영향과 이와연관된 apoptosis 유발 여부 및 관련 인자들의 발현 변화를 조사하였다. 먼저 GRW의 처리에 따른 증식억제 정도를 조사한 결과, GRW 처리 농도 의존적으로 생존율 및 증식억제 현상이 나타났으며, 핵의 형태 변화, DNA 단편화 및 apoptosis 유발에 관하여 조사한 결과 역시 GRW 처리 농도 의존적으로 증가됨을 확인할 수 있었다. 이는 GRW의 처리에 의한 암세포의 증식억제및 형태적 변형이 암세포의 apoptosis 유발과 밀접한 관련이 있음을 시사하여 주는 것으로 사료된다. GRW 처리에 의한 apoptosis 유발에 관여하는 유전자의 탐색을 위하여 apoptosis와 연관성을 가지는 Bcl-2 family에 속하는 유전자의 발현을 조사한 결과 GRW 처리 농도 의존적으로Bax 단백질의 발현증가와 더불어 Bcl-2 및 Bcl-xL 단백질의 발현감소가 관찰되었다(Fig. 3A). 이는 GRW에 의한 T24 세포의apoptosis 유발에 Bcl-2 family에 속하는 유전자의 발현 조절이 중요한 역할을 하는 것으로 사료된다. 또한 GRW의 처리에따른 MMP의 소실은 미트콘드리아 막의 교란이 유발되었음을의미하는 것으로, 이러한 MMP 값의 변동은 Bcl-2 family 단백질의 발현 변화에 의한 것이라 추정된다. 한편 Apoptosis에 중요한 역할을 하는 것으로 알려진 caspase(-3/-8/–9)의 발현과이들의 활성을 억제하는 IAP family (XIAP, cIAP-1, cIAP-2)의 발현에 GRW이 어떠한 영향을 미치는지를 조사한 결과, caspase-3, -8 및 -9의 활성형 단백질 발현 및 정량적 활성증가를 확인하였으며, IAP family 속한 3가지 단백질 모두 발현이감소하는 것이 관찰되었다. 이상의 결과에서 GRW은 외인적 및 내인적 경로의 개시에 핵심적인 역할을 하는 caspase-8 및 -9의 활성을 모두 증가시켰으며, 이에 따른 caspase-3의 활성증가에 의하여 apoptosis가유발되었음을 알 수 있었다. 이러한 두 경로의 동시 활성화에는미트콘드리아의 기능 소실과 Bcl-2 및 IAP family의 발현 변화가 관여하고 있었으며, 특히 Bid의 발현 감소는 GRW에 의한 내인적 경로를 증폭시키는 효과로 작용했을 것이라 추정된다. 방광암의 치료에 보다 효과적인 생리활성을 갖는 물질을 발굴하고 그와 관련된 분자 및 세포수준에서의 기전을 밝히는 것이 중요하기에 본 연구의 결과는 향후 GRW로 수행될 추가 실험을 위한 기초자료로서 그 가치가 매우 높을 것으로 사료된다.

무균성 뇌막염 환아의 말초혈액 단핵구의 Apoptosis에 관한 연구

김현영,김동수 대한감염학회 1999 감염 Vol.31 No.1

Dual role of reactive oxygen species in autophagy and apoptosis induced by compound PN in prostate cancer cells

최현덕,김광연,박광일,김상헌,Park Sul-Gi,Yu Sun-Nyoung,김영우,김동섭,정경태,안순철 대한독성 유전단백체 학회 2021 Molecular & cellular toxicology Vol.17 No.1

Background Pharbitis nil (L.) Choisy (PN) is used as a traditional herb in East Asia and exhibits anti-parasitic, purgative, diuretic, anti-inflammatory, and anti-cancer activities. However, the molecular mechanisms underlying the anti-cancer activity are not well understood. Objective This study aims to elucidate the effects of reactive oxygen species (ROS), generated after treatment with the compound PN, on the induction of apoptosis and autophagy, which are pathways that underly the mechanisms of cell death and cell survival in human prostate cancer cells. Results The MTT assay and western blot analysis were used to assess the effects of compound PN on cell viability and the expression of apoptosis- and autophagy-related proteins in prostate cancer PC-3 cells. The effects of PN on apoptosis (via annexin V/propidium iodide staining), autophagy (via acridine orange staining), and ROS (via DCFH-DA staining) were investigated using flow cytometry. Compound PN induced the production of intracellular and mitochondrial ROS leading to increased apoptosis and autophagy in PC-3 cells. Interestingly, pretreatment with N-acetyl-L-cysteine (NAC), an intracellular ROS scavenger, enhanced compound PN-induced apoptosis, but reduced levels of autophagy. In contrast, pretreatment with diphenyleneiodonium (DPI), an inhibitor of mitochondrial ROS, reduced compound PN-induced apoptosis and enhanced autophagy. Inhibition of autophagy led to acceleration of apoptosis in a PN-induced ROS-dependent manner. Compound PN-induced ROS production from two different sources, an intracellular source and mitochondrial source. ROS production in these differing locations had different effects on apoptosis and autophagy. They acted either by promoting cell death or cell survival through regulating autophagy to either escape or enhance apoptotic cell death. Conclusion This crosstalk between ROS-activated signals in apoptosis and autophagy induction by PN provides new insights into the molecular mechanisms of this compound and suggests that PN may be a potential therapy for prostate cancer treatment. Background Pharbitis nil (L.) Choisy (PN) is used as a traditional herb in East Asia and exhibits anti-parasitic, purgative, diuretic, anti-inflammatory, and anti-cancer activities. However, the molecular mechanisms underlying the anti-cancer activity are not well understood. Objective This study aims to elucidate the effects of reactive oxygen species (ROS), generated after treatment with the compound PN, on the induction of apoptosis and autophagy, which are pathways that underly the mechanisms of cell death and cell survival in human prostate cancer cells. Results The MTT assay and western blot analysis were used to assess the effects of compound PN on cell viability and the expression of apoptosis- and autophagy-related proteins in prostate cancer PC-3 cells. The effects of PN on apoptosis (via annexin V/propidium iodide staining), autophagy (via acridine orange staining), and ROS (via DCFH-DA staining) were investigated using flow cytometry. Compound PN induced the production of intracellular and mitochondrial ROS leading to increased apoptosis and autophagy in PC-3 cells. Interestingly, pretreatment with N-acetyl-L-cysteine (NAC), an intracellular ROS scavenger, enhanced compound PN-induced apoptosis, but reduced levels of autophagy. In contrast, pretreatment with diphenyleneiodonium (DPI), an inhibitor of mitochondrial ROS, reduced compound PN-induced apoptosis and enhanced autophagy. Inhibition of autophagy led to acceleration of apoptosis in a PN-induced ROS-dependent manner. Compound PN-induced ROS production from two different sources, an intracellular source and mitochondrial source. ROS production in these differing locations had different effects on apoptosis and autophagy. They acted either by promoting cell death or cell survival through regulating autophagy to either escape or enhance apoptotic cell death. Conclusion This crosstalk between ROS-activated signals in apoptosis and autophagy induction by PN provides new insights into the molecular mechanisms of this compound and suggests that PN may be a potential therapy for prostate cancer treatment.

Interferon-r가 대장암세포주 HT-29의 Fas 매개 세포사멸에 미치는 영향

강진경(Jin Kyung Kang),박인서(In Suh Park),김원호(Won Ho Kim),하성호(Sung Ho Ha) 대한소화기학회 1997 대한소화기학회지 Vol.29 No.5

N/A Background/Aims: Recent evidence suggests that alterations in regulation of apoptosis contribute to the pathogenesis of a number of human diseases, including cancer, viral infections, autoimmune diseases, degenerative diseases and inflammatory diseases. Fas antigen(APO-1, CD95) is a cell surface receptor protein that is broadly expressed in normal and neoplastic cells and can mediate apoptosis in susceptible cells. Fas is involved in immune-related apoptosis including T-cell selection in thymus, down regulation of immune response and cytotoxic T-cell mediated cytotoxicity. In contrast to immune system, little is known about the function of Fas antigen expressed on epithelial cells. We, therefore, studied the functional role of Fas in apoptosis of colon cancer cell line HT-29. Methods: Cell surface Fas expression was measured by flow cytometry using IgM anti-Fas monoclonal antibody(CH-11). Fas mRNA expression was measured by RT-PCR. Cytotoxicity and cell survival were assessed by LDH assay and MTT assay, respectively. Apoptosis was detected by confocal microscopic observation of chromatin condensation after DAPI stain and confirrned by dernonstration of DNA fragmentation in agarose gel electrophoresis as well as .TUNEL assay. DNA content was determined by flow cytometry after staining with propidium iodide and sub-Gl peak was considered as apoptotic cells. Results: Twenty to thirty percent of control HT-29 expressed Fas antigen on their surface. Nevertheless, Fas ligation by IgM anti-Fas monoclonal antibody(CH-11) failed to induce apoptosis in control HT-29. Fas protein as well as Fas mRNA expression was enhanced by IFN-y. In addition, Fas ligation in IFN-y pretreated HT-29 induced apoptosis dose-dependently. Cycloheximide and actinomycin D induced apoptosis in IFN-y pretreated HT-29, whereas they failed to induce apoptosis independently. Conclpsions: Fas antigen expressed on the surface of colon cancer cell line HT-29 is not sufficient to induce apoptosis. Cellular activation by IFN-y not only enhances Fas expression but also sensitizes HT-29 to Fas-mediated apoptosis. Apoptosis inducing effect of IFN-p pretreatment is complexly mediated by enhancing Fas expression as well as other mechanism yet undetermined. (Korean J Gastroenterol 1997, 29:620 - 631)

백서흉선세포에서 Apoptosis유발과 In Situ Labeling에 의한 DNA분절 검출

최종원,김정희,김시영,윤휘중,조경삼 大韓血液學會 1996 大韓血液學會誌 Vol.31 No.1

가토 허혈-재관류 심근에서의 Apoptosis에 대한 Superoxide Dismutase의 효과

김영권,박이태,김성숙 대한순환기학회 1997 Korean Circulation Journal Vol.27 No.9

인체백혈병 U937 세포에서 부처꽃 에탄올추출물에 의한 apoptosis 유도

정진우,김철환,이영경,황용,이기원,최경민,김정일 한국자원식물학회 2020 한국자원식물학회지 Vol.33 No.4

본 연구에서는 부처꽃 에탄올 추출물(ELM)에 대한 항암효능을 알아보기 위하여 인체백혈병 U937 세포의 증식에 미치는 영향과 이와 연관된 apoptosis 유발 여부와 함께 그에 따른 분자생물학적 기전에 대해서 조사하였다. 먼저 ELM 처리에 따른 증식억제 정도를 조사한 결과, ELM 처리 농도 의존적으로 생존율 및증식억제 현상이 나타났으며, 핵의 형태 변화, DNA 단편화 및apoptosis 유발에 관하여 조사한 결과 역시 ELM 처리 농도 의존적으로 증가됨을 확인할 수 있었다. ELM 처리에 따른 U937 세포에서의 apoptosis 유발에 있어서 미토콘드리아 막의 기능 손상이 관여하는 지를 확인하기 위하여 MMP의 변화 정도를 확인한 결과, ELM 처리 농도 증가에 따라 MMP의 소실이 증가하는것을 관찰할 수 있었다. 이러한 MMP의 소실에 가 관여하는 지를 확인하기 위하여 사멸수용체(DR4, 5, Fas) 및 사멸수용체에결합하는 리간드(FasL, TRAIL)의 발현 변화를 확인한 결과, DR4 및 DR5의 발현이 증가하는 것으로 관찰되었다. 또한 내인적 경로에 관여하는 Bcl-2 family 유전자들의 발현변화를 확인한 결과, Bcl-2 발현 감소 및 Bax의 발현 증가의 변화를 보였으며, Bid 단백질의 발현감소가 나타났으므로 상대적으로 tBid의생성이 증가되었음을 추측할 수 있었다. 한편apoptosis 유발에직접적으로 관여하는 것으로 알려진 caspase-3, -8 및 -9의 발현에 미치는 ELM의 영향에 대해서 조사하였다. 결과에서 알 수있듯이 ELM은 death receptor에 의하여 활성화 되는 것으로 알려진 caspase-8 및 세포질로 방출된 cytochrome c에 의하여 활성화 되는 것으로 알려진 caspase-9의 활성화를 유발하였으며, caspase cascade에 의하여 apoptosis에 직접적으로 관여하는caspase-3의 발현도 증가시키는 것으로 나타났다. 또한 활성화된 caspase-3에 의하여 분해가 일어나는 기질 단백질인PARP의 경우 ELM 처리에 의하여 모두 단편화가 유발되는 것으로 나타났다. 이상의 결과를 종합해 보면 인체 백혈병 U937 세포에 ELM을 처리하였을 경우에 유발되는 apoptosis는 외인적경로인 DR4 및 DR5의 발현 증가를 통한 caspase-8의 활성화와이로 인한 Bid 단백질의 단편화와 함께 내인적 경로의 미토콘드리아 기능 손실에 의하여 caspase-9 및 -3의 활성화 유발과 기질단백질들의 분해가 중요한 역할을 하는 것으로 생각되며, IAP family의 발현 감소로 인하여 caspase의 활성이 억제되지못하는 것도 apoptosis 유도에 어느 정도 관여했을 것으로 생각된다. 따라서 ELM 처리에 의하여 유발되는 apoptosis는 외인적경로 및 내인적 경로를 모두 경유하는 multiple apoptotic pathway에 의하여 조절되며, 이때 caspases가 중요한 역할을한다는 것을 알 수 있었다. Purple loosestrife-Lythrum anceps (Koehne) Makino is a herbaceous perennial plant belonging to the Lythraceae family. It has been used for centuries in Korea and other Asian traditional medicine. It has been showed pharmacological effects, including anti-oxidant and anti-microbial effects. However, the mechanisms underlying its anti-cancer effect are not yet understood. In this study, we investigated the mechanism of apoptosis signaling pathways by ethanol extract of Lythrum anceps (Koehne) Makino (ELM) in human leukemia U937 cells. Treatment with ELM significantly inhibited cell growth in a dose-dependent manner by inducing apoptosis, as evidenced by the formation of apoptotic bodies (ApoBDs), DNA fragmentation and increased populations of sub-G1 ratio. Induction of apoptosis by ELM was connected with up-regulation of death receptor (DR) 4 and DR5, pro-apoptotic Bax protein expression and down-regulation of anti-apoptotic Bcl-2 protein, and inhibitor of apoptosis protein (IAP) family proteins, depending on dosage. This induction was associated with Bid truncation, mitochondrial dysfunction, proteolytic activation of caspases (-3, -8 and –9) and cleavage of poly(ADP-ribose) polymerase protein. Therefore, our data indicate that ELM suppresses U937 cell growth by activating the intrinsic and extrinsic apoptosis pathways, and thus may have applications as a potential source for an anti-leukemic chemotherapeutic agent.

자외선 조사에 의한 인체 각질형성세포 세포고사 방어인자에 관한 연구

박수홍,박준홍,이종석,황규왕,김계정 순천향의학연구소 1998 Journal of Soonchunhyang Medical Science Vol.4 No.2

Back ground: Human skin is continuously exposed to UV irradiation. Ultraviolet irradiation of human skin cause sunburn cell which is relevant to the apoptosis of keratinocytes. In the epidermis, apoptosis inducing factors and anti-apoptotic factors probably exist to maintain the integrity of keratinocytes. Objective: The purpose of this study was to investigate the exsistence of apoptosis inducing factors and anti-apoptotic defence factors by evaluation of UV induced apoptosis in cultured human keratinocyte and other keratinocyte cell lines(A-431 cells, KB cells) and its susceptibility of UV induced apoptosis in various conditions. Method: In this study, the percentages of apoptosis, necrosis and cell viability of irradiated human keratinocytes and othe keratinocyte cell lines by MMT assay and AO/EO stain. The percentages of those were measured before UVB irradiation and 8, 24, 48 hours after UVB irradiation. Also, the same evaluations were performed with irradiated human keratinocytes cultured without growth factor and with enough growth factors, both results were compared with each other. And the effect of cycloheximide, a protein synthesis inhibitor was evaluated. Also that of aurintricarboxylic acid(ATA), an inhibitor of endonucleases which play an important role in inducing apoptosis of human keratinocytes was evaluated. Result: Human keratinocytes and other keratinocyte cell lines(A-431 cells, KB cells) were cultured in vitro developed maximal apoptosis 48 hours after irradiation, keratinocytes were more resistant to UV induced apoptosis than the others. The withdrawal of growth factors from keratinocyte and addition of cycloheximide decreased the cell survival rate following UV irradiation and increased the induction of apoptosis. And ATA inhibited UV induced apoptosis. Conclusion: These results indicate that human keratinocytes have both anti-apoptotic factors and apoptosis inducing factors to maintain the homeostasis. And survival signals mediated through growth factors or cellular proteins are responsible for the resistance to apoptosis observed in keratinocytes in vitro.