紫外线和人乳头状瘤病毒16 E6协同诱导、促进裸鼠皮肤鳞状细胞癌的机制研究

【摘要】 目的 构建裸鼠皮肤鳞状细胞癌（CSCC）移植瘤模型,探讨紫外线（UV）损伤及人乳头瘤病毒（HPV）感染诱导、促进CSCC的协同作用机制。方法 将人CSCC细胞A431分成3组,即用 HPV16 E6腺病毒转染的HPV16 E6 过表达组,空白腺病毒转染的空白载体组（简称空载组）,未进行腺病毒转染的空白对照组。使用无血清DMEM培养基将空载组及HPV16 E6过表达组（LV-OE-HPV16 E6组）A431细胞制成单细胞悬液,分别接种于SKH-1裸鼠左侧臀部皮下作为空载组（n = 16）和LV-OE-HPV16 E6组（n = 16）。每3天观察并记录小鼠肿瘤生长情况,当瘤体达到150 mm3时,视为建模成功。建模成功后,每组取8只小鼠进行UV照射,分为4组,即空载组、空载 + UV组、LV-OE-HPV16 E6组、LV-OE-HPV16 E6 + UV组,UV照射剂量为1 440 mJ/（cm2·d）,每次12 min,持续4周后处死裸鼠,测量瘤重及体积,绘制肿瘤生长曲线,免疫组化、Western印迹和qRT-PCR检测验证Wnt1、β联蛋白mRNA及蛋白在裸鼠CSCC中的表达。数据若符合正态分布,多组间比较采用方差分析,组间两两比较采用LSD-t检验;数据若不符合正态分布,采用秩和检验对数据进行统计分析。结果 空载 + UV组瘤重为（2.90 ± 0.36） g,LV-OE-HPV16 E6组（3.19 ± 0.32） g,LV-OE-HPV16 E6 + UV组（4.41 ± 0.18） g,与空载组（2.20 ± 0.24） g比较,差异均有统计学意义（t值分别为4.39、6.77、20.11,均P＜0.001）;空载 + UV组瘤体积为（1 033.12 ± 400.15） mm3,LV-OE-HPV16 E6组（1 119.21 ± 447.57） mm3,LV-OE-HPV16 E6 + UV组（1 464.29 ± 409.98） mm3,与空载组（688.94 ± 319.31） mm3比较差异均有统计学意义（t值分别为1.90、2.21、4.22,均P＜0.001）。免疫组化显示,4组间Wnt1、β联蛋白表达水平差异无统计学意义（F值分别为0.76、0.71,均P > 0.05）;Western印迹显示,4组间Wnt1、β联蛋白水平差异有统计学意义（F值分别为16.74、49.90,均P＜0.05）,且LV-OE-HPV16 E6 + UV组Wnt1、β联蛋白水平高于空载组、空载 + UV组和LV-OE-HPV16 E6组（均P＜0.05）。mRNA水平分析显示,4组间组织中Wnt1、β联蛋白mRNA水平差异均有统计学意义（F值分别为7.77、8.38,均P＜0.05）,且LV-OE-HPV16 E6 + UV组Wnt1 mRNA水平高于空载组、空载 + UV组和LV-OE-HPV16 E6组（均P＜0.05）。结论 UV和HPV感染在诱导、促进CSCC中具有协同作用。     

人乳头瘤病毒16型 E6通过微小RNA-504调控宫颈癌细胞增殖、侵袭和凋亡的研究

目的 探讨人乳头瘤病毒16型(HPV16)E6通过微小RNA(miR)-504对宫颈癌SiHa细胞增殖、侵袭和凋亡的影响。方法 将体外培养的SiHa细胞分为对照组、空载体组、E6过表达组、E6过表达+miR-NC组和E6过表达+miR-504组。采用实时荧光定量聚合酶链反应检测HPV16 E6 mRNA和miR-504的表达;采用免疫印迹法检测HPV16 E6蛋白表达;采用噻唑蓝(MTT)法、Transwell小室和流式细胞仪分别检测细胞增殖、侵袭和凋亡情况。结果 与对照组和空载体组比较,E6过表达组细胞中HPV16 E6蛋白和mRNA表达水平均明显升高,而miR-504表达水平降低(P<0.05);与对照组比较,E6过表达组细胞增殖活力和侵袭能力明显升高,而细胞凋亡率降低(P<0.05);与E6过表达组和E6过表达+miR-NC组比较,E6过表达+miR-504组细胞中miR-504表达水平和细胞凋亡率明显升高,而细胞增殖活力和侵袭能力明显降低(P<0.05)。结论 HPV16 E6可能通过下调miR-504的表达促进宫颈癌SiHa细胞的增殖、侵袭并抑制其细胞凋亡。     

宫颈癌组织中人乳头瘤病毒16型E6、人乳头瘤病毒16型E7蛋白表达及DNA病毒载量与调节性T细胞浸润的相关性分析

目的 探究宫颈癌组织中人乳头瘤病毒16型(HPV16)E6、HPV16 E7蛋白表达及DNA病毒载量与调节性T(Treg)细胞浸润的相关性及临床意义。方法 选取成都医学院第一附属医院2018年1月至2020年1月84例行手术治疗的宫颈癌患者的癌组织作为宫颈癌组,选取同一医院同期手术治疗的42例宫颈上皮内瘤变(CIN)患者的宫颈组织作为CIN组,另选取42例因子宫肌瘤行全子宫切除术的患者的正常宫颈组织作为正常组。对比分析三组组织中HPV16 E6、HPV16 E7蛋白表达及DNA病毒载量、Treg细胞浸润的情况。结果 宫颈癌组HPV16 E6、HPV16 E7蛋白阳性表达率及DNA病毒载量、Treg细胞占CD4⁺T细胞比例均高于CIN组、正常组,CIN组上述指标均高于正常组(P<0.05);宫颈癌组织中HPV16 E6、HPV16 E7蛋白阳性表达率及DNA病毒载量与Treg细胞占CD4⁺T细胞比例呈正相关(P<0.05);HPV16 E6、HPV16 E7蛋白阳性表达率及DNA病毒载量、Treg细胞占CD4⁺...     

慢病毒介导的靶向沉默HPV16E7-shRNA对SiHa细胞DNA甲基转移酶表达的影响

目的 探讨慢病毒携带的靶向人乳头瘤病毒16(HPV16)E7基因的短发夹干扰RNA(shRNA)对HPV16阳性宫颈癌SiHa细胞中4种甲基转移酶(DNMT1、DNMT3A、DNMT3B、DNMT3L)表达水平的影响.方法 构建HPV16 E7基因靶序列的shRNA重组质粒,用BLOCK-iTTM Lentiviral RNAi Expression System试剂盒进行慢病毒包装,分别转染293T细胞48、72 h后收集病毒上清液.分别用含靶向HPV 16 E7-shRNA重组质粒的病毒上清液与完全培养基(1∶1)的混合液(shRNA组)、含空白质粒(即不含靶向HPV16 E7-shRNA序列)的病毒上清液与完全培养基(1∶1)的混合液(阴性对照组)、完全培养基(空白对照组)培养SiHa细胞.感染0、48、96 h后,用实时荧光定量PCR(qRT-PCR)检测3组SiHa细胞中HPV16 E7和4种甲基转移酶mRNA的表达,Western印迹检测4种甲基转移酶的蛋白表达.结果 感染0h时,shRNA组、阴性对照组、空白对照组SiHa细胞HPV16 E7、DNMT1、DNMT3A、DNMT3B、DNMT3L mRNA相对表达量比较,差异无统计学意义(均P＞0.05);感染48、96 h时,3组细胞间HPV16 E7和4种DNMT mRNA相对表达量比较,差异有统计学意义(均P＜0.05).shRNA组HPV16 E7、DNMT1、DNMT3A、DNMT3B和DNMT3L mRNA表达水平在48 h时的沉默效率分别为71.13％、50.53％、13.72％、46.27％和17.92％,96 h时分别为83.50％、74.2％、47.8％、64.7％和48.9％;而阴性对照组和空白对照组各时间点表达水平差异无统计学意义(均P＞0.05).慢病毒感染48、96 h时,3组细胞间上述4种DNMT蛋白表达量差异有统计学意义(均P＜0.01).shRNA组4种DNMT蛋白表达水平随感染时间的延长而逐渐下降,感染48 h时DNMT1、DNMT3A、DNMT3B和DNMT3L蛋白表达抑制率分别为84％、37.2％、59.8％、49.3％,96 h时分别为73.1％、68.7％,55.5％、65.5％.结论 靶向沉默HPV16阳性宫颈癌SiHa细胞E7基因能够干扰DNMT1、DNMT3A、DNMT3B、DNMT3L mRNA及蛋白的表达.     

扁平苔藓皮损中肿瘤坏死因子α和半胱氨酸天冬氨酸蛋白酶8、3的表达

目的 研究扁平苔藓皮损中肿瘤坏死因子α(TNF-α)、半胱氨酸天冬氨酸蛋白酶8(Caspase-8)和Caspase-3的表达及意义.方法 采用免疫组化法和原位末端标记技术(TUNEL)检测20例扁平苔藓患者皮损和20例健康人皮肤组织中TNF-α、Caspase-8、Caspase-3的表达和细胞凋亡情况.采用SPSS 11.5统计软件,组间比较采用成组t检验,指标间相关性采用Pearson相关分析.结果 扁平苔藓组TNF-α、Caspase-8和Caspase-3的积分光密度值分别为12580±2330、11690±3520和11450±2820,均明显高于健康对照组(分别为5120±1780、3870±3360、4760±1930),两组比较,t值分别为11.38、7.19、8.76,P值均＜0.01;扁平苔藓组角质形成细胞凋亡指数(71.35±7.93),明显高于健康对照组(33.62±8.75),两组比较,t=14.29,P＜ 0.01.扁平苔藓组TNF-α、Caspase-8的表达强度与角质形成细胞凋亡指数间均呈正相关,r分别为0.72、0.75,P值均＜0.01;同时两者与Caspase-3的阳性表达也均呈正相关,r分别为0.68、0.73,P值均＜0.01.结论 TNF-α、Caspase-8和Caspase-3的高表达可能参与了扁平苔藓中角质形成细胞的凋亡.     

HPV16E7靶向小干扰RNA对SiHa细胞增殖凋亡及6种抑癌基因的影响

目的：探讨HPV16E7在SiHa细胞株中对抑癌基因（MT1G、NMES1、RRAD、SFRP1、SPARC、TFPI2）的表达及细胞增殖能力和凋亡水平的影响。方法 SiHa细胞转染E7SiRNA 48 h后,qPCR检测E7及6种抑癌基因mRNA水平变化,CCK?8检测细胞增殖能力改变,流式细胞仪检测细胞凋亡水平。结果 SiHa细胞转染后48 h,qPCR结果显示实验组E7 mRNA显著降低（0.25±0.036,P<0.05）;6种抑癌基因的mRNA水平均显著增加（MT1G 1.403±0.190、NMES11.720±0.060、RRAD 1.390±0.160、SFRP11.493±0.120、SPARC 2.157±0.144、TFPI22.060±0.122,P<0.05）。细胞增殖结果显示,与阴性对照组及空白组比较,实验组细胞增殖能力显著降低（0.554±0.130,P<0.05）,阴性对照组和空白组之间差异无统计学意义（P>0.05）。细胞凋亡结果提示,实验组细胞凋亡细胞频率为9.222%较阴性对照组（0.246%）及空白组（0.123%）明显增加（P<0.05）,空白组与阴性对照组差异无统计学意义（P>0.05）。结论 HPV16导致细胞恶性转化过程中,E7可能通过抑制（MT1G、NMES1、RRAD、SFRP1、SPAR、TFPI2）6种抑癌基因的表达参与作用。     

稳定表达人乳头瘤病毒16E7蛋白HaCaT细胞株的建立

目的建立稳定表达人乳头瘤病毒(HPV)16E7蛋白的HaCaT细胞株.方法利用PCR及酶切技术扩增出CaSki细胞中HPV16E7基因并定向克隆到真核细胞表达载体pcDNA3.1(+)中,构建真核表达质粒pcDNA3.1(+)-HPV16E7.将重组质粒转染入HaCaT细胞,经G418筛选稳定表达HPV16E7蛋白的细胞株并予以鉴定.结果经酶切、测序鉴定构建pcDNA3.1(+)-HPV16E7成功.RT-PCR扩增产物经琼脂糖凝胶电泳后检测到HPV16E7mRNA表达的特异性297 bp条带;Western印迹可检测到E7蛋白稳定表达.结论成功构建出稳定表达HPV16E7蛋白的HaCaT细胞株.     

稳定表达人乳头瘤病毒16E7蛋白HaCaT细胞株的建立

目的建立稳定表达人乳头瘤病毒(HPV)16E7蛋白的HaCaT细胞株.方法利用PCR及酶切技术扩增出CaSki细胞中HPV16E7基因并定向克隆到真核细胞表达载体pcDNA3.1(+)中,构建真核表达质粒pcDNA3.1(+)-HPV16E7.将重组质粒转染入HaCaT细胞,经G418筛选稳定表达HPV16E7蛋白的细胞株并予以鉴定.结果经酶切、测序鉴定构建pcDNA3.1(+)-HPV16E7成功.RT-PCR扩增产物经琼脂糖凝胶电泳后检测到HPV16E7mRNA表达的特异性297 bp条带;Western印迹可检测到E7蛋白稳定表达.结论成功构建出稳定表达HPV16E7蛋白的HaCaT细胞株.     

稳定表达人乳头瘤病毒16E7蛋白HaCaT细胞株的建立

目的建立稳定表达人乳头瘤病毒(HPV)16E7蛋白的HaCaT细胞株.方法利用PCR及酶切技术扩增出CaSki细胞中HPV16E7基因并定向克隆到真核细胞表达载体pcDNA3.1(+)中,构建真核表达质粒pcDNA3.1(+)-HPV16E7.将重组质粒转染入HaCaT细胞,经G418筛选稳定表达HPV16E7蛋白的细胞株并予以鉴定.结果经酶切、测序鉴定构建pcDNA3.1(+)-HPV16E7成功.RT-PCR扩增产物经琼脂糖凝胶电泳后检测到HPV16E7mRNA表达的特异性297 bp条带;Western印迹可检测到E7蛋白稳定表达.结论成功构建出稳定表达HPV16E7蛋白的HaCaT细胞株.     

成纤维细胞生长因子受体3与人乳头瘤病毒2型E2对角质形成细胞分化的初步研究

目的研究成纤维细胞生长因子受体3(FGFR3)与人乳头瘤病毒2型(HPV2)E2对人角质形成细胞系HaCaT和正常人表皮角质形成细胞系NHEK分化的调控效应。方法在HaCaT和NHEK细胞中, 采用慢病毒转染法构建HPV2 E2稳转细胞系(HPV2 E2转染组), 采用质粒转染法构建过表达FGFR3或FGFR3突变体K650E的细胞, 即FGFR3-WT转染组、FGFR3-K650E转染组, 均以转染空载体的细胞为空载体对照组。采用实时荧光定量PCR检测HPV2 E2 mRNA表达, Western印迹法检测HPV2 E2、FGFR3及角质形成细胞分化标志性分子兜甲蛋白、聚丝蛋白、内披蛋白的表达。激光共聚焦显微镜观察HPV2 E2与FGFR3的细胞空间定位。两组数据比较采用独立样本t检验, 多组间比较采用单因素方差分析, 组间两两比较采用Dunnett-t检验。结果成功构建HPV2 E2稳转细胞系, HaCaT和NHEK细胞中HPV2 E2转染组HPV2 E2 FLAG蛋白表达量均显著高于空载体对照组(t值分别为13.71和25.91, 均P < 0.001);在HaCaT和NH...     

Cutaneous squamous cell carcinoma and human papillomavirus

The relationship between mucosal human papillomavirus (HPV) and cervical carcinoma or anogenital squamous cell carcinoma (SCC) is becoming increasingly evident, whereas a link between HPV and other cutaneous SCCs is less clear. Recent studies have reported links between epidermodysplasia-verruciformis-associated HPV and extragenital cutaneous SCC, particularly in immunosuppressed patients, although immunocompetent patients have also been affected. Mucosal HPV could also be linked to some types of Bowen disease and certain SCCs of the fingers, oropharyngeal mucosa, etc. We review the possible oncogenic mechanisms involving mucosal HPV and epidermodysplasia-verruciformis-associated HPV. Most SCCs could be explained by the combined action of HPV, immunosuppression, and the oncogenic and immunosuppressive effect of UV radiation. HPV might be associated with worse prognosis of SCC, with implications for clinical practice including greater risk of metastasis.     

Characteristics of an epidermal cell thymocyte-activating factor (ETAF) produced by human epidermal cells and a human squamous cell carcinoma cell line

In this study we show that both cultured normal human epidermal cells (EC) and a human squamous cell carcinoma (SCC) cell line produce a thymocyte-activating factor (ETAF). EC-ETAF and SCC-ETAF both have a Mr of 15,000 and were eluted from chromatofocusing at the same isoelectric points of 7.2, 5.8, and 5.0. Both activities were maintained at alkaline pH and were destroyed at temperatures above 60 degrees C. In addition to stimulating thymocyte proliferation, human ETAF exhibited a variety of other pertinent biologic activities. Although EC-ETAF or SCC-ETAF by themselves exhibited no T-cell growth factor activity, both ETAF preparations enhanced Interleukin 2 production by cultured human peripheral blood lymphocytes when stimulated with polyclonal T-cells stimulants (Concanavalin A and phorbol myristate acetate). Human ETAF also was chemotactic for rabbit polymorphonuclear leukocytes and was directly mitogenic for cultured human dermal fibroblasts. Injection of human ETAF into C3H/HeJ mice, resulted in inducing serum amyloid A (SAA) production by murine hepatocytes. The thymocyte growth-enhancing activity, the fibroblast-stimulating activity, and the SAA-inducing capacity of ETAF all coeluted off AcA54 gel. These biologic as well as biochemical properties of human keratinocyte-derived ETAF are identical with those of human macrophage-derived Interleukin 1. The ability of keratinocytes to release an immunomodulating factor with such diverse consequences may play an important role in normal wound healing and in diseases involving epithelial tissues.     

Local injection of recombinant human stem cell factor promotes human skin mast cell survival and neurofibroma cell proliferation in the transplanted neurofibroma in nude mice

Abstract We studied the effects of stem cell factor (SCF) on human skin mast cell (HSMC) survival and the proliferation of neurofibroma (NF) cells in transplanted NF in nude mice. Small pieces of cutaneous NF from a patient with von Recklinghausen’s disease were transplanted subcutaneously into nude mice. Recombinant human SCF (10 or 100 ng) was injected six or seven times around the NF transplantation sites over 11 days (i.e. every other day). The number of HSMCs was reduced in vehicle-injected NF compared to the amount present before transplantation. In contrast, NF-transplanted animals that were injected with SCF (10 or 100 ng) showed preservation of mast cell numbers in the tissue. Using computerized image analysis, mast cell size in SCF-treated NF transplants was significantly altered (larger at the 10 ng dose, and smaller at the 100 ng dose) compared with the size before transplantation or in vehicle-injected tissue. Furthermore, at the higher SCF dose (100 ng) PCNA-positive NF cells showed a significant increase. These results indicate that HSMCs in transplanted NF tissue retain their capacity to respond to SCF in vivo, and that SCF contributes to the regulation of both HSMC survival and size in cutaneous NF. In addition, activated HSMCs induced by SCF may be involved in the growth of cutaneous NF in von Recklinghausen’s disease. Thus, this experimental model may be useful in the study of the cellular interactions between HSMCs and other stromal cells in cutaneous NF. Received: 9 June 1998 / Received after revision: 30 November 1998 / Accepted: 11 December 1998     

Mast cell survival and apoptosis in organ-cultured human skin

Mast cells accumulate and persist predominantly in the upper dermis of the skin but the mechanism for this is obscure. The skin is normally exposed to external air, which is essential for the maturation of the epidermis and probably also the dermis. In order to clarify the importance of air exposure on dermal mast cells, skin organ culture at the air-liquid interface (ALI) and submerged (SM) in medium (10% fetal calf serum and Dulbecco's modification of Eagle's medium) was used to study changes in tryptase-, chymase- and Kit-positive mast cell numbers during cultivation for up to 14 days. In addition, possible apoptosis (TACS TdT in situ apoptosis detection method) in chymase-positive mast cells was studied during the culture. In the less-physiologic SM culture, the number of Kit-positive mast cells decreased rapidly on day 1-2 and tryptase-positive cells decreased markedly on day 14. This decrease in mast cell numbers can be explained by the finding that a rapid increase in the apoptosis index of mast cells was induced on day 1-2. In contrast, in the more physiologic ALI culture, the number of Kit-positive cells was sustained over 1-2 days but then decreased on day 7. In addition, tryptase-positive cells decreased steadily in number but not to the same extent as those in the SM culture. Moreover, the increase in the apoptosis index of mast cells was delayed until day 7 in the ALI culture. Addition of exogenous stem cell factor (up to 200 ng/ml) to the SM culture could not prevent the decay in tryptase- and chymase-positive cells. However, stem cell factor reduced significantly the number of Kit-positive cells already on day 2 indicating that the cells had responded. Addition of histamine (0.25 or 1 mM) or tumor necrosis factor-alpha (500 or 2000 U/ml) caused a decrease in the number of tryptase- and Kit-positive cells in the SM culture. In conclusion, a novel finding was that air exposure in the ALI culture markedly delayed the rapid apoptosis and subsequent decrease in mast cell numbers noted to occur in the SM culture. Stem cell factor could not prevent the rapid decrease in mast cell numbers. Histamine and tumor necrosis factor-alpha are possible factors promoting the decline in mast cells.     

Investigating human keratinocyte stem cell identity

Studies of the regulatory networks controlling intrinsic properties and fate of adult stem cells are in a large part performed in animal models. Epidermis is one of the most accessible human tissues for researchers, which is a critical parameter for conducting programs dedicated to this knowledge in human stem cell systems. Keratinocyte stem cells constitute a particularly valuable model, because of this practical aspect, but more importantly because their existence is for decades validated by the clinical demonstration of their impressive capacity for epidermis regeneration. For the fundamentalist, human keratinocyte stem cells represent a unique system to dissect the genetic and epigenetic controls of "stemness" and self-renewal. For this purpose, a highly limiting point is our current inability of obtaining a cellular material corresponding to keratinocyte stem cells with homogeneous phenotypic and functional characteristics. The search for tools suitable for the prospective selection of keratinocyte stem cells will benefit from studies conducted at the broad level of the global stem cell field, as well as from more specifically targeted approaches. Advances in that direction are tightly linked to the development of functional assays allowing reliable assessment and modeling of the different stem cell-associated functional characteristics.     

Langerhans cell histiocytosis-clinicopathological reappraisal and human leucocyte antigen association

Summary We have examined the clinicopathological correlates of 74 patients with histologically confirmed Langerhans cell histiocytosis. Factors that influenced disease outcome included, three or more organs/systems being involved, a disease onset before the age of 2 years, the involvement of certain vital organs/systems such as liver/spleen, bone marrow and lungs, and male gender. The total number of involved organs/systems was the single most important determinant of disease outcome. Mortality rate in patients with three or more organs/systems involved, was 26%, as compared with 0% in the group with one or two organs/systems involved (χ²= 11.2, P = 0.008). There were no familial cases in our series, but we looked for a possible immunogenetic association by tissue typing 46 Caucasian sufferers and comparing the results with 117 controls. We used normal peripheral blood lymphocytes in 39 cases, Epstein-Barr virus-transformed lymphoblastoid cell lines in 12 cases, and both peripheral blood and Epstein-Barr virus-transformed lymphocytes in five cases. The HLA-B7 antigen was significantly increased in Langerhans cell histiocytosis patients (19 of 46 = 41.3%) compared with 19 of 117 (16.2%) in the control group (χ²= 11.2, relative risk = 3.6, P value after correction = 0.013). Attempt to stratify the disease into single-system or multisystem disease did not result in any significant association.     

Ras oncogene mutations in basal cell carcinomas and squamous cell carcinomas of human skin

Activated ras oncogenes have been detected in a variety of human malignancies. Activation of ras oncogenes usually occurs by point mutations within specific codons of the H-ras, N-ras, and K-ras genes. For the present study, DNA was isolated from 30 basal cell carcinomas (BCC) and 12 squamous cell carcinomas (SCC). After amplification of genomic DNA by using the polymerase chain reaction, the occurrence of point mutations was investigated with 32P-labeled synthetic oligonucleotides. These probes are complementary to the known point-mutated nucleotide sequences of the ras genes. In four out of the 30 BCC studied, point mutations were detected at codon 12 of the K-ras gene and at codon 61 of the H-ras gene. The K-ras mutations involve glycine to cysteine and glycine to asparagine amino acid changes. The mutation at codon 61 of the H-ras gene is consistent with a replacement of glutamine by histidine. In one SCC, a point mutation was detected at codon 12 of the K-ras gene, involving a glycine to cysteine substitution in the gene product. These findings demonstrate that mutational activation of ras genes takes place in skin carcinomas, but the rate at which these mutations occur seems to be relatively low.     

Differential expression of mast cell characteristics in human myeloid cell lines

In order to better understand the mechanisms governing display of mast cell characteristics in human myeloid cells, we have studied the mast cell phenotype in human promyelocytic (HL-60) and myelocytic (U-937, TPH-1) vs. basophilic (KU-812) and mast cell (HMC-1) lines, in part also in skin mast cells and blood monocytes, at mRNA and protein level before and after stimulation with mast cell growth factors. In unstimulated cells, mRNA for the stem cell factor (SCF) receptor c-kit and the gamma chain of the high-affinity IgE receptor (FcepsilonRI) was noted in all cells studied. Like mast and basophilic cells, THP-1 cells expressed the FcepsilonRIalpha and beta chains and weakly histidine decarboxylase (HDC), but they lacked mRNA for mast cell-specific proteases [tryptase, chymase, carboxypeptidase A (CPA)]. In contrast, HL-60 and U-937 cells lacked FcepsilonRIalpha, but expressed tryptase and chymase, HL-60 cells also CPA. KU-812 cells failed to express the basophil-specific marker 2D7. After a 10-day culture with SCF or fibroblast supernatants, baseline mRNA expression of most mast cell characteristics was upregulated, whereas c-kit mRNA expression decreased in all but THP-1 cells. Differential mRNA expression of FcepsilonRI vs. protease (tryptase) was confirmed at protein level by immunocytochemistry and enzymatic activity. KU-812 cells are thus closest to skin mast cells in that they express all molecules studied, except for chymase, followed by THP-1 cells that lack all mast cell proteases. In contrast, HL-60 and U-937 cells fail to express the FcepsilonRIalpha and beta chains but express most mast cell proteases. The selective and differential expression of mast cell characteristics in human myeloid cell lines suggests that induction of the mast cell phenotype is regulated by several independent genes and that mast cells and basophils branch off at early and distinct points of myeloid development.