Icaritin induces growth inhibition and apoptosis of human prostatic smooth muscle cells in an estrogen receptor-independent manner

Icaritin has selective estrogen receptor (ER) modulating activity. ERs are expressed in the prostate stroma, and estrogens have an important role in the pathology of benign prostatic hyperplasia (BPH). However, the impact of icaritin on BPH was not studied. Human prostatic smooth muscle cells (PSMCs) were treated with 0–100 μM icaritin, also using 10 μM ICI182780 as a specific ER antagonist. The effects on cell growth and apoptosis were determined by cell counting and sandwich-enzyme-immunoassay. Western blotting was employed to illustrate the possible mechanisms. Cell growth was strongly inhibited by icaritin, and this was accompanied by an augmented apoptosis. Few changes in icaritin-induced growth inhibition and apoptosis were observed after pretreatment in the presence of ICI182780. Consistent with growth inhibition and apoptosis induction, icaritin decreased cyclin D1 and CDK4 expression and increased Bax/Bcl-2 ratio in human PSMCs. Furthermore, icaritin induced sustained phosphorylation of extracellular signal-regulated kinase (ERK) in human PSMCs. PD98059, a specific ERK inhibitor, blocked the activation of ERK by icaritin and abolished the icaritin-induced growth inhibition and apoptosis. The results indicate that icaritin reduces growth and induces apoptosis in human PSMCs via ERK signaling pathway without involvement of ERs.     

Construction of NF-κB-targeting RNAi adenovirus vector and the effect of NF-κB pathway on proliferation and apoptosis of vascular endothelial cells

To construct a recombinant adenovirus vector expressing a RNAi for the Nuclear Factor kappa B (NF-κB)/p65 gene and use it to explore the role of the NF-κB pathway on the regulation of proliferation and apoptosis of vascular endothelial cells. A recombinant adenovirus containing a RNAi cassette targeting the p65 gene was constructed, and its silencing effect on p65 was detected by Western blot analysis in ECV304 cells. Expression of the p65 protein in ECV304 cells was efficiently down-regulated by the RNAi adenovirus for more than 6 days. ECV304 cells proliferation and apoptosis were measured using the MTT assay and flow cytometry, respectively. Blocking the NF-κB pathway with the RNAi adenovirus substantially decreased the proliferation of ECV304 cells, but only slightly affected cell apoptosis. We used a NF-κB/p65-targeting RNAi adenovirus to demonstrate the role of the NF-κB pathway in the regulation of ECV304 cell proliferation. This adenovirus may serve as an important tool to study the NF-κB pathway.     

The effect of NF-��B pathway on proliferation and apoptosis of human umbilical vein endothelial cells induced by intermittent high glucose

Our previous study found that blocking nuclear factor (NF)-κB signaling could protect human umbilical vein endothelial cells (HUVECs) from apoptosis and proliferation inhibition due to high glucose (HG). Intermittent HG makes glucose toxicity more significant. In this study, we aimed to investigate the effect of NF-κB pathway on HUVECs induced by intermittent HG (a daily alternating 5.5 or 30.5 mmol/l glucose). A recombinant adenovirus containing a RNAi cassette targeting the NF-κB/p65 gene was produced, and its silencing effect on p65 gene was detected by Western blot analysis in HUVECs cultured with intermittent HG. The subsequent effect on proliferation of HUVECs in the indicated conditions was measured by the AlamarBlue assay. The Bcl-2 expression was also detected by Western blot. The results showed that the expression of p65 protein could be inhibited efficiently by the RNAi adenovirus. Intermittent HG also induced the translocation of NF-κB in HUVECs. Inhibition of NF-κB with the RNAi adenovirus could prevent the effects. At the 6th day after HUVECs were exposed to intermittent HG, the proliferation of HUVECs with Ad-1566 was significantly higher than that of HUVECs with Ad-DEST (P < 0.01). Knockdown of NF-κB/p65 up-regulated the Bcl-2 expression of HUVECs under intermittent HG conditions (P < 0.01). These findings concluded that the NF-κB/p65-targeting RNAi adenovirus is an important tool, which can efficiently inhibit the expression of p65 gene in HUVECs. Intermittent HG reduces HUVECs proliferation with a concomitant increase in apoptosis. Knockdown of NF-κB/p65 partly protected HUVECs from proliferation inhibition and may reduce apoptosis.     

Regulation of GSK-3 beta in the proliferation and apoptosis of human thyrocytes investigated using a GSK-3 beta-targeting RNAi adenovirus expression vector: involvement the Wnt/beta-catenin pathway

Disorders in the proliferation and apoptosis of thyrocytes may induce goitre, adenoma and carcinoma in the thyroid. The Wnt/beta-catenin pathway has been demonstrated to be involved in the regulation of cell proliferation, differentiation and apoptosis in various cell lines. The regulatory mechanism on the proliferation and differentiation of thyrocytes is not well characterized. In the present study, a GSK-3beta-targeting RNA interference (RNAi) adenovirus vector was constructed and delivered to primary human thyrocytes. Results showed that the expression of beta-catenin protein in primary human thyrocytes was increased after GSK-3beta-targeting RNAi adenovirus infection, the proliferation of primary human thyrocytes was significantly stimulated using Bromodeoxyuridine (BrdU) assay, while cell apoptosis was slightly affected which was observed through flow cytometry. It is concluded that the Wnt/beta-catenin pathway plays a significant role in the regulation of the proliferation of primary human thyrocytes.     

17beta-estradiol affects proliferation and apoptosis of rat prostatic smooth muscle cells by modulating cell cycle transition and related proteins

Abundant evidence indicates that estrogens have an important role in the pathology of benign prostatic hyperplasia (BPH). To investigate the effect of 17beta-estradiol (E2) on the proliferation and apoptosis of prostatic smooth muscle cells (PSMCs), rat PSMCs were obtained and exposed to gradient concentrations (0.1-100 nmol/l) of E2 over varying amounts of time. The progression of cell cycle, cellular apoptosis, cyclin D1, Bcl-2 and Bax proteins were detected. The data show that the effect of E2 on rat PSMCs is bilateral: it promotes cell proliferation by enhancing the expression of cyclin D1, which accelerates G1 to S phase transition; on the other hand, it induces apoptosis of the cells by up-regulating the expression of Bax. We thus suggest that an increase in estrogen may exert a launching effect in the pathology of BPH.     

High FFA-induced proliferation and apoptosis in human umbilical vein endothelial cell partly through Wnt/β-catenin signal pathway

Free fatty acids (FFA)-induced proliferation and apoptosis was studied in human umbilical vein endothelial cells (HUVECs). A recombinant adenovirus containing a RNAi cassette targeting the GSK-3β gene was produced and its silencing effect on GSK-3β gene was detected by Western blot analysis and immunohistochemistry assay in HUVECs. The effect of the RNAi on the protein level of β-catenin was explored by transfecting the RNAi adenovirus to inhibit the expression of GSK-3β protein. The subsequent effect on the Wnt/GSK-3β/β-catenin signal pathway and on proliferation and apoptosis of HUVECs cultured with FFAs, was analyzed by BrdU assay, Annexin V-FITC/PI Apoptosis Detection Kit, and 4′,6-diamidino-2- phenylindole(DAPI) to explore the possible connection between the signaling pathway and FFA-induced proliferation and apoptosis. The Western blot results showed that the expression of GSK-3β protein in HUVECs could be inhibited efficiently by the RNAi adenovirus, and that the protein level of β-catenin was increased by RNAi adenovirus transfection. The results of the BrdU assay suggested that knockdown of GSK-3β with the RNAi adenovirus may stimulate the proliferation of HUVECs. Apoptosis was observed in HUVECs exposed to FFAs (0.75 mmol/L) for 72 h, and this effect could be partly reversed when interfering with the RNAi adenovirus. It may be concluded that the RNAi adenovirus specific to GSK-3β may partly protect HUVECs from apoptosis induced by FFAs, probably through the up-regulation of the Wnt/β-catenin signal pathway.     

RNA Interference-Mediated Inhibition of Wild-Type Torsin A Expression Increases Apoptosis Caused by Oxidative Stress in Cultured Cells

To assess RNAi mediated inhibition of the expression of wt-DYT1 on H₂O₂-induced toxicity in NIH 3T3 cells and primary cortical neurons. To detect the function of wild-type Torsin A and the effect of SiRNA on the wt-DYT1 gene. The shRNA expression vector was constructed by ligating annealed complementary shRNA oligonucleotides into the down-stream of the human U6 promoter (PU6) of the RNAi-ready pSIREN-Shuttle vector. Then, the pSIREN-Shuttle-DYT1-shRNA cassette was ligated to Adeno-X Viral DNA to construct the recombinant adenoviral vector pAd-DYT1-shRNA. Cultured cerebral cortical neurons and NIH 3T3 cells were transfected with pAd-DYT1-shRNA and pSIREN-Shuttle-DYT1-shRNA. We evaluated NIH 3T3 cells and neurons in the presence of oxidative stress using a TUNEL assay under different conditions. The knockdown efficacy of the DYT1 was confirmed by real-time RT-PCR and Western Blot analysis. After exposure to H₂O_2, the quantity of NIH 3T3 cells transfected with pSIREN-Shuttle-DYT1-shRNA, which stained positively in the TUNEL assay, was significantly higher than the cells transfected with pSIREN-Shuttle-negative control-shRNA. (44.85 ± 1.81% vs. 8.98 ± 2.73%, t = 26.168). There were significantly more apoptotic neurons infected with pAd-DYT1-shRNA (45.63 ± 7.53%) than neurons infected with pAd-X-negative control-shRNA (17.33 ± 2.43%) (t = 9.816). The observed silencing of wild-type Torsin A expression by DYT1-shRNA was sequence-specific. RNAi-mediated inhibition of the expression of wild-type Torsin A increases apoptosis caused by oxidative stress. It is reasonable to consider that wild-type Torsin A has the capacity to protect cortical neurons against oxidative stress, and in the development of DYT1-delta GAG-dystonia the neuroprotective function of wild-type Torsin A may be compromised.     

Gel-based application of siRNA to human epithelial cancer cells induces RNAi-dependent apoptosis

Gene silencing by RNA interference (RNAi) operates at the level of mRNA that is targeted for destruction with exquisite sequence specificity. In principle, any disease-related mRNA sequence is a putative target for RNAi-based therapeutics. To develop this therapeutic potential, it is necessary to develop ways of inducing RNAi by clinically acceptable delivery procedures. Here, we ask if inducers of RNAi can be delivered to human cells via a gel-based medium. RNAi was induced using synthetic small interfering RNAs (siRNAs), which bypass the need for expression vectors and carry the added bonus of high potency and immediate efficacy. Established cultures of human cells of normal and tumor origin were overlaid with an agarose/liposome/siRNA gel formulation without adverse effects on cell viability or proliferation. Epithelial cancer cells (but not normal human fibroblasts) proved vulnerable to specific siRNAs delivered via the agarose/liposome/siRNA formulation. Moreover, proapoptotic siRNAs induced apoptosis of cervical carcinoma cells (treated with human papillomavirus [HPV] E7 siRNA) and of colorectal carcinoma cells (treated with Bcl-2 siRNA). Thus, we demonstrate successful topical gel-based delivery of inducers of RNAi to human epithelial cancer cells. Topical induction of RNAi opens an important new therapeutic approach for treatment of human diseases, including cervical cancer and other accessible disorders.     

Bcl-2/C-Raf双基因“敲低”抑制人结肠癌细胞增殖

 RNA干扰是一种具有序列特异性的基因沉默,能够触发具有相应序列的mRNA的降解.构建具有双靶点的RNAi质粒表达载体,与单靶点表达载体比较,探讨其对结肠癌细胞增殖的抑 制作用.本研究分别构建了针对Bcl-2、C-Raf 和Bcl-2/C-Raf靶基因的质粒表达载体,通过Lipofectamine TM2000介导转染人结肠癌细胞系HCT-8后,检测相应转染组靶基因的mRNA和蛋白质表达量,测定各组细胞活性,研究RNAi对各组癌细胞增殖的抑制率.结果表明,分别转染3种质粒表达载体后,3组结肠癌细胞中相应靶基因的mRNA和蛋白质表达量均降低;转染双靶点干扰质粒的试验组;其细胞活性低于单靶点组;对于针对Bcl-2, C-Raf和Bcl-2/C-Raf基因的3组干扰实验,RNAi对结肠癌细胞增殖的抑制率分别为43.87%,40.64% 和63.85%.RNAi是结肠癌细胞中的一种功能途径,以质粒作为表达载体,同时具备Bcl-2/C-Raf双靶点的表达载体,对结肠癌细胞增殖的抑制作用要明显优于单靶点表达载体,双靶点质粒表达载体在结肠癌的基因治疗中是有潜力的.     

METTL3 promotes prostatic hyperplasia by regulating PTEN expression in an m6A-YTHDF2-dependent manner

Uncontrolled epithelial cell proliferation in the prostate transition zone and the hyper-accumulation of mesenchymal-like cells derived from the epithelial-mesenchymal transition (EMT) of prostatic epithelium are two key processes in benign prostatic hyperplasia (BPH). m⁶A RNA modification affects multiple cellular processes, including cell proliferation, apoptosis, and differentiation. In this study, the aberrant up-regulation of methylase METTL3 in BPH samples suggests its potential role in BPH development. Elevated m⁶A modification in the prostate of the BPH rat was partially reduced by METTL3 knockdown. METTL3 knockdown also partially reduced the prostatic epithelial thickness and prostate weight, significantly improved the histological features of the prostate, inhibited epithelial proliferation and EMT, and promoted apoptosis. In vitro, METTL3 knockdown decreased TGF-β-stimulated BPH-1 cell proliferation, m⁶A modification, and EMT, whereas promoted cell apoptosis. METTL3 increased the m⁶A modification of PTEN and inhibited its expression through the reading protein YTHDF2. PTEN knockdown aggravated the molecular, cellular, and pathological alterations in the prostate of BPH rats and amplified TGF-β-induced changes in BPH-1 cells. More importantly, PTEN knockdown partially abolished the improving effects of METTL3 knockdown both in vivo and in vitro. In conclusion, the level of m⁶A modification is elevated in BPH; the METTL3/YTHDF2/PTEN axis disturbs the balance between epithelial proliferation and apoptosis, promotes EMT, and accelerates BPH development in an m⁶A modification-related manner.Subject terms: Cell biology, Molecular biology     

Delivery of short hairpin RNAs by transkingdom RNA interference modulates the classical ABCB1-mediated multidrug-resistant phenotype of cancer cells

Delivery of RNA interference (RNAi)-mediating agents to target cells is one of the major obstacles for the development of RNAi-based therapies. One strategy to overcome this barrier is transkingdom RNAi (tkRNAi). This technology uses non-pathogenic bacteria to produce and deliver therapeutic short hairpin RNA (shRNA) into target cells to induce RNAi. In this study, the tkRNAi approach was used for modulation of the “classical” ABCB1-mediated multidrug resistance (MDR) in human cancer cells. Subsequent to treatment with anti-ABCB1 shRNA expression vector bearing E. coli, MDR cancer cells (EPG85 257RDB) showed 45% less ABCB1 mRNA expression. ABCB1 protein expression levels were reduced to a point at which merely a weak band could be detected. Drug accumulation was enhanced 11-fold, to an extent that it reached 45% of the levels in non-resistant cells and resistance to daunorubicin was decreased by 40%. The data provide the proof-of-concept that tkRNAi is suitable for modulation of “classical” MDR in human cancer cells. Overall, the prototype tkRNAi system tested here did not yet attain the levels of gene silencing seen with conventional siRNAs nor virally delivered shRNAs; but the tkRNAi system for gene-silencing of ABCB1 is still being optimized, and may become a powerful tool for delivery of RNAi effectors for the reversal of cancer MDR in future.     

Effect of keratinocyte growth factor on cell viability in primary cultured human prostate cancer stromal cells

In normal prostate, keratinocyte growth factor (KGF), also known as fibroblast growth factor-7 (FGF-7) serves as a paracrine growth factor synthesized in stromal cells that acts on epithelial cells through its receptor, KGFR. KGF and KGFR were found in human cancer epithelial cells as well as stromal cells. Since KGF expressed in epithelial cells of benign prostatic hyperplasia (BPH) and in prostate cancer, it has been suggested that KGF might act as an autocrine factor in BPH and prostate cancer. To investigate the roles of KGF in cancerous stroma, primary cultured human prostate cancer stromal cells (PCSCs) were isolated and evaluated. These PCSCs possessed estrogen receptors and KGFR, but not androgen receptor as determined by RT-PCR and Western blot, respectively. KGF exhibited mitogenic and anti-apoptotic effects that correlated with induction of cyclin-D1, Bcl-2, Bcl-xL and phospho-Akt expression in PCSCs, where treatment with KGF antiserum abolished cell proliferation and anti-apoptotic protein expression. PCSCs exposed to KGF for various time periods resulted in phosphorylation of Akt and subsequent up-regulation of Bcl-2. KGF modulated dynamic protein expression indicated that KGF triggered cell cycle machinery and then activated anti-apoptotic actions in PCSCs. Cell proliferation analysis indicated that tamoxifen or ICI 182,780 reduced cell viability in a dose-dependent manner; however, KGF prevented this inhibition, which further demonstrated KGF triggered anti-apoptotic machinery through activating Bcl-2 and phospho-Akt expression. In summary, KGF has an autocrine effect and serves as a survival factor in primary cultured human prostate cancer stromal cells.     

腺病毒载体AdING4 对MCF-7乳腺癌细胞的增殖抑制及化疗增敏作用

目的:研究腺病毒载体AdING4对人MCF-7乳腺癌细胞的生长抑制及化疗增敏作用。方法:将搭载有ING-4基因的重组腺病毒载体AdING4感染人MCF-7乳腺癌细胞,用荧光显微镜观察感染后的MCF-7细胞形态学变化;RT-PCR和Western-Blot法检测ING-4基因在MCF-7细胞中的转录和表达;RT-PCR法检测凋亡相关基因在MCF-7细胞中的表达;CCK法测定Ad-ING4感染MCF-7乳腺癌细胞后所发挥的细胞增殖抑制作用。流式细胞技术检测ING-4对MCF-7乳腺癌细胞的促凋亡作用。CCK-8法分别测定病毒感染前后的MCF-7乳腺癌细胞的药物半数抑制浓度IC50,并观察Ad-ING4与化疗药物合用后对MCF-7细胞增殖抑制和化疗增敏现象。结果:MCF-7细胞在转染ING-4基因后,明显出现变圆、脱落、皱缩、聚集等现象;外源性ING-4基因在MCF-7细胞中获得成功表达;外源性ING-4基因作用下MCF-7细胞的增殖受到了明显抑制,凋亡率有所升高,凋亡相关基因Bax的表达水平明显上调,Bcl-2、Survivin的表达水平明显下调。ING-4基因感染MCF-7细胞后,使MCF-7细胞对相关化疗药物的敏感度更高;ING-4基因与化疗药物合用后对MCF-7细胞的增殖抑制作用,较之单用化疗药物更为明显。结论:MCF-7细胞在转染ING4基因后其增殖受到了明显抑制并更易凋亡,该现象可能是通过改变Bax,Bcl-2及Survivin表达水平来实现的,且对化疗药物的敏感性更高。     

Immunoexpression of tumour necrosis factor-alpha and its receptors 1 and 2 correlates with proliferation/apoptosis equilibrium in normal, hyperplasic and carcinomatous human prostate

Immunohistochemical and semiquantitative study of TNF-alpha, its receptors types 1 (TNFR1) and 2 (TNFR2), cell proliferation (Ki-67 nuclear antigen), and apoptosis (Tunel method) was carried out in human prostates, in normal healthy conditions, as well as in benign prostatic hyperplasia (BPH) and prostatic carcinoma (PC). Cell proliferation was higher in BPH than in normal prostates, and even higher in PC, mainly in neoformations showing a microglandular pattern. The apoptotic index was similar in BPH and normal prostates, and increased significantly in PC with independence of the pattern. In BPH, immunoreaction to TNF-alpha decreased as compared with that of normal prostates, while immunoreactions to both TNF-alpha receptors increased. This suggests a feedback downregulation of the factor, and that the low TNF-alpha activity in BPH are compensated by the increased amount of receptors. In PC, immunoreaction to TNF-alpha and its two receptors increased markedly, suggesting that the TNF-induced effects are also increased. Contrarily to cell proliferation immunoexpression, PC reaction to TNFR2 was stronger in the papillar pattern than in the micrograndular pattern, and this suggests an inverse correlation between TNFR2 expression and cell proliferation.     

Ad-IL-24对人胶质瘤细胞生长抑制效应的体外实验

研究携带人白介素24(IL-24)的腺病毒表达载体(Ad-IL-24)对人U251胶质瘤细胞生长的影响和抗肿瘤分子机制。将不同MOI Ad-IL-24感染U251人胶质瘤细胞后, MTT法检测Ad-IL-24对U251细胞生长的抑制作用, 流式细胞仪和Hochest 染色法检测细胞的凋亡率。RT-PCR检测bcl-2、bax、ICE、C-myc、HIF-1a和p53等基因的转录表达水平, Western blotting检测Cleaved Caspase-3的表达。结果表明100 MOI Ad-IL-24感染U251细胞后能明显抑制细胞生长, 并能明显诱导细胞凋亡, 感染72 h后细胞凋亡率可达42%, 感染4 d后细胞生长抑制率可达50%。RT-PCR检测发现Ad-IL-24能引起与细胞凋亡和血管形成相关基因bax/bcl-2、ICE、C-myc、p53的上调和HIF-1a的下调, 并促进Caspase-3的活化。本研究结果显示Ad-IL-24能明显抑制人胶质瘤细胞U251生长和诱导细胞凋亡, 其抗肿瘤机制可能与通过bax/ bcl-2、ICE、c-myc、p53的上调和HIF-1a的下调, 进而导致Caspase-3的活化而诱导肿瘤细胞发生凋亡有关。     

Bcl-2 decreases voltage-gated K+ channel activity and enhances survival in vascular smooth muscle cells

Cell shrinkage is an incipient hallmark of apoptosis in a variety of cell types. The apoptotic volume decrease has been demonstrated to attribute, in part, to K+ efflux; blockade of plasmalemmal K+ channels inhibits the apoptotic volume decrease and attenuates apoptosis. Using combined approaches of gene transfection, single-cell PCR, patch clamp, and fluorescence microscopy, we examined whether overexpression of Bcl-2, an anti-apoptotic oncoprotein, inhibits apoptosis in pulmonary artery smooth muscle cells (PASMC) by diminishing the activity of voltage-gated K+ (Kv) channels. A human bcl-2 gene was infected into primary cultured rat PASMC using an adenoviral vector. Overexpression of Bcl-2 significantly decreased the amplitude and current density of Kv currents (I(Kv)). In contrast, the apoptosis inducer staurosporine (ST) enhanced I(Kv). In bcl-2-infected cells, however, the ST-induced increase in I(Kv) was completely abolished, and the ST-induced apoptosis was significantly inhibited compared with cells infected with an empty adenovirus (-bcl-2). Blockade of Kv channels in control cells (-bcl-2) by 4-aminopyridine also inhibited the ST-induced increase in I(Kv) and apoptosis. Furthermore, overexpression of Bcl-2 accelerated the inactivation of I(Kv) and downregulated the mRNA expression of the pore-forming Kv channel alpha-subunits (Kv1.1, Kv1.5, and Kv2.1). These results suggest that inhibition of Kv channel activity may serve as an additional mechanism involved in the Bcl-2-mediated anti-apoptotic effect on vascular smooth muscle cells.     

Characterisation and application of a bovine U6 promoter for expression of short hairpin RNAs

Background  

The use of small interfering RNA (siRNA) molecules in animals to achieve double-stranded RNA-mediated interference (RNAi) has recently emerged as a powerful method of sequence-specific gene knockdown. As DNA-based expression of short hairpin RNA (shRNA) for RNAi may offer some advantages over chemical and in vitro synthesised siRNA, a number of vectors for expression of shRNA have been developed. These often feature polymerase III (pol. III) promoters of either mouse or human origin.     

Functional complementation of the adenovirus E1B 19-kilodalton protein with Bcl-2 in the inhibition of apoptosis in infected cells.

Expression of the adenovirus E1A oncogene induces apoptosis which impedes both the transformation of primary rodent cells and productive adenovirus infection of human cells. Coexpression of E1A with the E1B 19,000-molecular-weight protein (19K protein) or the Bcl-2 protein, both of which have antiapoptotic activity, is necessary for efficient transformation. Induction of apoptosis by E1A in rodent cells is mediated by the p53 tumor suppressor gene, and both the E1B 19K protein and the Bcl-2 protein can overcome this p53-dependent apoptosis. The functional similarity between Bcl-2 and the E1B 19K protein suggested that they may act by similar mechanisms and that Bcl-2 may complement the requirement for E1B 19K expression during productive infection. Infection of human HeLa cells with E1B 19K loss-of-function mutant adenovirus produces apoptosis characterized by enhanced cytopathic effects (cyt phenotype) and degradation of host cell chromosomal DNA and viral DNA (deg phenotype). Failure to inhibit apoptosis results in premature host cell death, which impairs virus yield. HeLa cells express extremely low levels of p53 because of expression of human papillomavirus E6 protein. Levels of p53 were substantially increased by E1A expression during adenovirus infection. Therefore, E1A may induce apoptosis by overriding the E6-induced degradation of p53 and promoting p53 accumulation. Stable Bcl-2 overexpression in HeLa cells infected with the E1B 19K- mutant adenovirus blocked the induction of the cyt and deg phenotypes. Expression of Bcl-2 in HeLa cells also conferred resistance to apoptosis mediated by tumor necrosis factor alpha and Fas antigen, which is also an established function of the E1B 19K protein. A comparison of the amino acid sequences of Bcl-2 family members and that of the E1B 19K protein indicated that there was limited amino acid sequence homology between the central conserved domains of E1B 19K and Bcl-2. This domain of the E1B 19K protein is important in transformation and regulation of apoptosis, as determined by mutational analysis. The limited sequence homology and functional equivalency provided further evidence that the Bcl-2 and E1B 19K proteins may possess related mechanisms of action and that the E1B 19K protein may be the adenovirus equivalent of the cellular Bcl-2 protein.