细胞凋亡调节与宫颈癌发生

目的：探讨子宫颈癌发生中的影响细胞凋亡的调节因素。方法：检测对象为194例经福尔马林固定石蜡包埋的手术切除标本，包括上皮内瘤样病变（CIN）78例[其中重度非典型增生（SD）41例；原位癌（CIS）37例]早期浸润癌（MIC）35例；大细胞非角化型浸润癌（IC）40例及正常宫颈鳞状上皮（NE）41例。凋亡细胞的检出使用TDT－mediated dUTP-biotin nick end labeling(TUNEL)方法；细胞凋亡相关基因蛋白p53、bcl-2、bax的表达采用单克隆抗体免疫组化ABC染色方法；HPV16、18型E6 DNA感染使用PCR方法进行检测。结果：1）凋亡细胞标记率仅在CIN呈现有意义地进行性减少（P＜0．01），癌变以后不再继续下降；2）在SD、CIS组，p53、bcl-2及bax基因蛋白的表达与TUNEL标记率呈现有意义地相关性变化（P＜0．05）；3）HPV16、18型E6 DNA感染与凋亡细胞及相关基因蛋白表达未呈现相关性改变。结论：以上结果提示细胞凋亡的改变与宫颈癌发生的早期过程有关，p53、bcl-2、bax基因蛋白参与其调节，而HPV16、18型E6 DNA感染与其未呈现直接的相关性。     

Changes in p21WAF1, pRb, Mdm-2, Bax and Bcl-2 expression in cervical cancer cell lines transfected with a p53 expressing adenovirus

The aim of this study was to provide some insights into the molecular mechanisms involved in p53-dependent apoptosis and growth arrest. Changes in the levels of p53 protein and proteins regulated by p53 were studied in relation to events of the cell cycle and apoptosis in cervical cancer cell lines upon transfection with a p53 expressing adenovirus (Ad5-p53). The post-transfection level of p53 protein in SiHa cells was found to be unchanged during the 24-48 h period. In contrast, the level of p21WAF1 protein was shown to increase to its highest level at 24 h, and decreased gradually up to 48 h after the Ad5-p53 transfection. We further noted that the increase of p21WAF1 was accompanied by G1 arrest at 24 h and the decrease of p21WAF1 was associated with apoptosis at 36-48 h after transfection. An anti-p21WAF1 antibody cross-reactive protein band of approximately 14 kDa was observed in HeLa and C-33A cells when these cells were committed to apoptosis upon Ad5-p53 transfection. In SiHa cells, phosphorylation of pRb was inhibited during the early stage of Ad5-p53 transfection. This was followed by the cleavage of pRb. However, Ad5-p53 transfection did not change the levels of Bax and Bcl-2 proteins. Our results suggested that, Bax and Bcl-2 may not be important for the apoptosis of these cells, whereas cleavage of Rb, and the decrease of p21WAF1 could play important roles in p53-dependent apoptosis.     

Bcl-2 is an apoptotic target suppressed by both c-Myc and E2F-1.

Malignant transformation occurs in cells that overexpress c-Myc or that inappropriately activate E2F-1. Transformation occurs after the selection of cells that have acquired resistance to apoptosis that is triggered by these oncogenes, and a key mediator of this cell death process is the p53 tumor suppressor. In IL-3-dependent immortal 32D.3 myeloid cells the ARF/p53 apoptotic pathway is inactivated, as these cells fail to express ARF. Nonetheless, both c-Myc and E2F-1 overexpression accelerated apoptosis when these cells were deprived of IL-3. Here we report that c-Myc or E2F-1 overexpression suppresses Bcl-2 protein and RNA levels, and that restoration of Bcl-2 protein effectively blocks the accelerated apoptosis that occurs when c-Myc- or E2F-1-overexpressing cells are deprived of IL-3. Blocking p53 activity with mutant p53 did not abrogate E2F-1-induced suppression of Bcl-2. Analysis of immortal myeloid cells engineered to overexpress c-Myc and E2F-1 DNA binding mutants revealed that DNA binding activity of these oncoproteins is required to suppress Bcl-2 expression. These results suggest that the targeting of Bcl-2 family members is an important mechanism of oncogene-induced apoptosis, and that this occurs independent of the ARF/p53 pathway.     

Laryngeal cancer and human papillomavirus: HPV is absent in the majority of laryngeal carcinomas

Thirty laryngeal carcinomas from patients without pre-existing laryngeal papillomatosis were examined by PCR for the presence of HPV DNA. The utmost care was taken during sectioning of the tissue blocks and DNA-extraction in order to avoid false positive results. Three pairs of consensus primers were used: MY9/MY11, GP5+/GP6+ and CPI/CPII. HPV was detected in 1/30 carcinomas. The HPV type present could not be determined, but it was not type 6, 11, 13, 16, 18, 30, 31, 33, 35 or 45. In other studies the reported frequency of HPV in laryngeal carcinomas, as estimated by PCR, varies between 3-85%. The reasons for this unacceptable variation in reported results are discussed. The present results indicate that HPV DNA does not have a major role in malignant tumours of the larynx in patients without pre-existing recurrent laryngeal papillomatosis.     

Human papillomavirus type 16 and 18 infection is associated with lung cancer patients from the central part of China

Infection with specific high-risk human papillomavirus (HPV) types 16 and 18 have been strongly associated with the genesis of various neoplasms in humans, though such study in lung cancer is limited and the results are controversial. In the present study, we collected and explored 313 fresh lung tumor specimens for the presence of HPV with polymerase chain reaction and non-isotopic in situ hybridization. We found that 44.1% of (138/313) non-small cell lung carcinoma (NSCLC) samples were positive for HPV detection, while 4.2% (4/96) of lung benign controls were positive for HPV 16 and 18 DNA. HPV infection was significant between lung squamous cell carcinoma and adenocarcinoma as well as smoking and non-smoking patients. In HPV-positive lung cancer tissues, abnormal p53 protein accumulation was seen in 97 of the 138 carcinomas (70.3%) and expression of pRb in 54 of the 138 carcinomas (39.1%). There was an obvious relationship between the presence of papilloma viral DNA and abnormal p53 protein accumulation and pRb depletion. Cell proliferation and apoptosis were correlated with HPV infection in NSCLC samples. Our data confirm the high prevalence of HPV in lung carcinomas in the central part of China and suggest the possible mechanism of the carcinogenic role of HPV in these carcinomas.     

Expression patterns of cyclins D1, E in laryngeal epithelial lesions: correlation with other cell cycle regulators (p53, pRb, Ki-67 and PCNA) and clinicopathological features

The expression of cell-cycle progression molecules cyclin D1 and cyclin E were immunohistochemically examined in a series of 64 squamous cell invasive carcinomas of the larynx, 10 in situ carcinomas, 34 cases of dysplasia, 11 papillomas and 23 cases of keratosis. The results of their expression were compared with two cell-cycle implicated tumor suppressor proteins p53 and pRb as well as with two proliferation associated indices PCNA and Ki-67 in an attempt to elucidate their potential role in the pathogenesis and progression of these lesions. Nuclear staining for cyclin D1 and E (>5% positive cells) was observed in 19% and 39.7% of the laryngeal carcinomas, respectively. Significantly elevated levels of cyclin D1 and E in invasive laryngeal carcinomas compared with in situ carcinomas were revealed (p=0.045 and p=0.0003, respectively). High levels of cyclin D1 and E expression were correlated with increased Ki-67 score (p=0.037 and 0.017 respectively). A significant positive correlation between cyclin D1 and E was also detected in carcinomas (p=0.018). Decreased levels of cyclins D1 and E in the group of in situ carcinomas compared with those of dysplastic cases and papillomas were also observed. In the dysplastic lesions cyclin D1 expression was correlated with pRb expression (p=0.02). In the cases of keratosis cyclins D1 and E expression were correlated with pRb (p=0.002 and p=0.036, respectively), while cyclin D1 was associated with PCNA (p=0.008) and Ki-67 score (p=0.009). The prognostic significance of cyclins D1, E in determining the risk of recurrence and overall survival with both univariate (long-rang test) and multivariate (Cox regression) methods of analysis showed no statistically significant differences. We conclude that the expression of cyclins D1 and E in squamous cell carcinomas of the larynx does not seem to have a prognostic significance. In addition, their expression may be involved in the development of laryngeal lesions, implicated in cell proliferation, with other cell cycle related proteins, probably by different molecular pathways.     

喉癌及喉良性病变中HPV不同亚型的检测

目的：检测喉癌、癌前病变及喉良性病变HPVDNA表达的阳性率,探讨HPV感染与喉癌发的相关性。方法：运用流式荧光杂交法以及型特异性PCR方法对于46例喉癌组织、14例喉癌前病变组织及19例喉良性病变组织中HPVDNA进行检测分型。结果：运用流式荧光杂交法在79例喉病变标本中检测HPVDNA阳性率为10．13％,其中46例喉癌阳性率为6．52％;癌前病变组阳性率为35．71％;喉良f生病变均为阴性。型特异性PCR方法检测出2例喉癌HPV16阳性,与流式荧光杂交法所检测到的2例相同。结论：HPV是喉乳头状瘤的一个独立的致病因素,而与喉癌的发生关系似乎不是很密切,但尚待进一步大样本研究。     

Decreased programmed cell death in the uterine cervix associated with high risk human papillomavirus infection

The relationship between apoptosis, apoptosis regulatory proteins, cell proliferation and human papillomavirus infection during various phases of tumor progression in the uterine cervix was studied. Apoptosis was defined by morphological criteria and the TUNEL assay. Expression of p53, bcl-2, bax, cyclin D1, Ki 67 and E6 protein was evaluated by immunocytochemistry. Presence of mutant p53 was detected using a mutant specific ELISA. Type of HPV infection was determined by PCR using type specific primers. Apoptosis showed significant negative correlation with increasing histological abnormality (p=0.0005). Higher tumor cell proliferation was associated with increasing histological abnormality (p=0.001 for Ki 67 and cyclin D1). There was significant correlation between histological grade and immunoreactivity of p53 (p=0.0001 ) and bcl-2 (p=0.0002). However, mutant p53 was expressed by only 12 of the 230 samples. Expression of bax and the bax/bcl-2 ratio showed an inverse correlation to histological grade (p=0.0003 and 0.0001, respectively). There was also an inverse correlation between extent of apoptosis and immunoreactivity of p53 (p=0.0001) and bcl-2 (p=0.0001). A significant positive correlation between expression of the bax protein and apoptosis was evident (p=0.0001). HPV infection significantly correlated to the extent of histological abnormality (p=0.0001). High risk HPV-E6 protein also showed this significant correlation (p=0.0002). There was an inverse correlation between apoptosis and HPV infection (p=0.0002). High risk HPV infection was associated with decreased apoptosis and also increased human cell proliferation. Lowest levels of bax/bcl-2 ratio was also associated with HPV 16 and 18 infection (p=0.0001). Modulation of apoptosis and apoptotic regulatory proteins by high risk HPV infection may be an important factor in the development of cervical cancer.     

Role of Human Papilloma Virus in Oral Tongue Squamous Cell Carcinoma

Background: Human papilloma virus (HPV) is an important risk factor for head and neck cancer, specificallyoropharyngeal cancer, but its association with oral tongue squamous cell carcinoma (SCC) is uncertain. Theobjectives were to determine the HPV16 prevalence in oral tongue SCCs, its integration status and to correlatethe expression of oncogenic proteins with targets. Methods: In this case-control study with oral tongue SCC cases(n=60) and normal oral mucosa (n=46), HPV positivity was determined by polymerase chain reaction (PCR)using consensus and HPV 16 type specific primers and p16 immunohistochemistry (IHC). The viral integrationstatus was determined with primers specific to the E2 gene and in situ hybridization (ISH). Immunohistochemicalanalysis of HPV oncogenic proteins (E6, E7) and their target proteins (p53, pRb, cyclinD1, p16, Notch-1, EGFR)proteins was carried out in HPV positive cases. The data was analyzed with SPSS software (v 11.0). Survivalanalysis was carried out by the Kaplan-Meier method. Results: HPV16 was detected in 48% (n=29) of the casesand none of the controls by PCR assay (p<0.001) while p16 IHC, as a surrogate HPV marker, detected 33%(n=18) of the cases; 18% (n=10) were detected by both the methods. Integration was observed in 83% (n=24)by E2-PCR and 67% (n=18) by ISH. The E6-p53 pathway was active in 33% of the cases; E7-pRb in 52% andboth in 11%. HPV positivity was associated with well-differentiated cancers (p=0.041) and low recurrence rate(p=0.014). Conclusion: Our study confirms a positive correlation of HPV infection with oral tongue cancer.     

Withaferin A induces p53-dependent apoptosis by repression of HPV oncogenes and upregulation of tumor suppressor proteins in human cervical cancer cells

Cervical cancer is caused by human papilloma virus (HPV) expressing E6 and E7 oncoproteins, which are known to inactivate tumor suppressor proteins p53 and pRb, respectively. Repression of HPV oncoproteins would therefore result in reactivation of tumor suppressor pathways and cause apoptosis in cancer cells. Withaferin A (WA), the active component of the medicinal plant Withania Somnifera, has exhibited inhibitory effects against several different cancers. We examined the activity of WA on human cervical cancer cells in vitro and in vivo. WA potently inhibited proliferation of the cervical cancer cells, CaSki (IC(50) 0.45 ± 0.05 μM). Mechanistically, WA was found to (i) downregulate expression of HPV E6 and E7 oncoproteins, (ii) induce accumulation of p53, (iii) increase levels of p21(cip1/waf1) and its interaction with proliferating cell nuclear antigen (PCNA), (iv) cause G(2)/M cell cycle arrest, associated with modulation of cyclin B1, p34(cdc2) and PCNA levels, (v) decrease the levels of STAT3 and its phosphorylation at Tyr(705) and Ser(727) and (vi) alter expression levels of p53-mediated apoptotic markers-Bcl2, Bax, caspase-3 and cleaved PARP. In vivo, WA resulted in reduction of nearly 70% of the tumor volume in athymic nude mice with essentially similar trend in the modulation of molecular markers as in vitro. This is the first demonstration indicating that WA significantly downregulates expression of HPV E6/E7 oncogenes and restores the p53 pathway, resulting in apoptosis of cervical cancer cells. Together, our data suggest that WA can be exploited as a potent therapeutic agent for the treatment and prevention of cervical cancer without deleterious effects.     

Chemosensitivity and p53-Bax pathway-mediated apoptosis in patients with uterine cervical cancer.

OBJECTIVES: To determine whether and how apoptosis through the p53-Bax pathway affects sensitivity to chemotherapy in cervical cancer. MATERIALS AND METHODS: Thirty patients with cervical squamous cell carcinoma, who had human papilloma virus (HPV) and underwent neoadjuvant chemotherapy, were entered in the present study. Tumor specimens were obtained before and after chemotherapy. HPV was detected by polymerase chain reaction. The expression of Ki-67, p53, Bax and Bcl-2 proteins was determined by immunohistochemical staining. Apoptotic cells were identified by the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate biotin nick-end labeling method. RESULTS: Of 30 patients, 18 responded to chemotherapy and 12 did not. The apoptotic index in tumors of responders was significantly higher than in non-responders after chemotherapy. The Ki-67 labeling index (LI) in responders was significantly higher than in non-responders before chemotherapy. Patients with tumors >33% of the LI, which was determined by a receiver operating characteristic curve, had a better survival rate. The incidence of p53 protein expression did not differ between responders and non-responders. After chemotherapy, the expression of Bax protein in responders was more frequent and Bcl-2 protein expression was less frequent than in non-responders. CONCLUSIONS: Chemosensitivity in cervical cancer may be associated with apoptosis via the p53-Bax pathway.     

NF-rBp50、p53、Bcl-2在宫颈癌组织中的表达及其与人乳头瘤病毒感染的关系

Objective： To explore the relationship between expressions of NF-κBp50, p53 and Bcl-2 in tissue of cervical cancer and human papillomavirus （HPV） infection. Methods： The expressions of NF-κBp50, p53 and Bcl-2 were detected using immuohistochemical staining in 46 specimens of cervical cancer and 26 specimens of normal cervical tissue. The infection of HPV DNA were determined by PCR. Results： The expressions of NF-κBp50, p53 and Bcl-2 in tissue of cervical cancer were significantly higher than that in normal cervical tissue （P〈0.01）, and the expressions of NF-κBp50 and p53 or Bcl-2 were closely related （P〈0.05）. The expression of NF-κBp50 in HPV DNA positive group was significantly higher than that in HPV negative group （P〈0.05）, but there were no significantly differences in the expressions of p53 and Bcl-2 between HPV DNA positive group and HPV negative group （P〉0.05）. Conclusion： The expressions of NF-κBp50, p53 and Bcl-2 were significantly correlated with cervical carcinogenesis. NF-κBp50 may be activated by HPV infection.     

E2F-1 up-regulates c-Myc and p14(ARF) and induces apoptosis in colon cancer cells.

Although overexpression of E2F-1 can induce apoptosis in a variety of tumor cell lines, the mechanisms by which E2F-1 induces apoptosis remain ambiguous. In this study, we examine the ability of E2F-1 to induce apoptosis in colon cancer and the molecular mechanisms underlying E2F-1-mediated apoptosis. HT-29 and SW-620 colon adenocarcinoma cells (both mutant p53) were treated by mock infection or adenoviral vectors Ad5CMV (empty vector), Ad5CMVLacZ (beta-galactosidase), and Ad5CMVE2F-1 (E2F-1) at multiplicity of infection of 100. Western blot analysis confirmed marked overexpression of E2F-1 in both cell lines. By 5 days after infection, E2F-1 overexpression resulted in >25-fold reduction in cell growth and >90% loss of cell viability in both cell lines. Cell cycle analysis of Ad-E2F-1-infected cells revealed an increase in G(2)/M and sub-G(1) populations. By in situ terminal deoxynucleotidyl transferase (Tdt)-mediated nick end labeling analysis, evidence of apoptosis was observed including internucleosomal DNA fragmentation and the formation of apoptotic bodies. In addition, caspase-3 and poly(ADP-ribose) polymerase apoptotic fragments were detected by 48 h after treatment with Ad-E2F-1. Of mechanistic importance, overexpression of E2F-1 caused a G(2)/M arrest followed by increased levels of c-Myc and p14(ARF) proteins. Additionally, expression of the antiapoptotic Bcl-2 family member Mcl-1 was down-regulated in E2F-1-overexpressing cells. In conclusion, E2F-1 overexpression initiates apoptosis and suppresses growth in HT-29 and SW620 colon adenocarcinoma cells. Overexpression of E2F-1 triggers apoptosis and is associated with up-regulation of c-Myc and p14(ARF) proteins and down-regulation of Mcl-1. Therefore, E2F-1 is a potentially active gene therapy agent for the treatment of colon cancer.     

EGCG induces apoptosis in human laryngeal epidermoid carcinoma Hep2 cells via mitochondria with the release of apoptosis-inducing factor and endonuclease G

(−)-Epigallocatechin-3-gallate (EGCG), a major green tea polyphenol, was tested for in vitro cytotoxicity against human laryngeal epidermoid carcinoma of the larynx Hep2 cells. EGCG-induced apoptotic cell death accompanied by a change in the cell cycle. However, EGCG did not result in caspase activation, nor did a caspase inhibitor block cell death. Furthermore, EGCG caused no change in the intracellular levels of reactive oxygen species (ROS). The levels of p53 were increased in the EGCG-treated cells, with a corresponding decrease in Bcl-2 and Bid protein levels as well as an increase in the Bax level. In addition, EGCG induced the cytoplasmic release of cytochrome c from the mitochondria accompanied by a decreased mitochondrial membrane potential, and subsequently upregulated translocation of apoptosis-inducing factor (AIF) and endonuclease G (EndoG) into the nucleus during the apoptotic process. Taken together, these findings indicate that the p53-mediated mitochondrial pathway and the nuclear translocation of AIF and EndoG play a crucial role in EGCG-induced apoptosis of human laryngeal epidermoid carcinoma Hep2 cells, which proceeds through a caspase-independent pathway.     

抑癌基因和凋亡调节蛋白在人乳腺癌中的表达及其相互关系

目的 观察乳腺癌组织、癌旁相对正常乳腺组织中抑癌基因p53和凋亡调节蛋白Bcl-2的表达,探讨Bcl-2和p53在乳腺癌发生、发展过程中的作用及其相互关系.方法 收集21例手术切除的人乳腺癌组织和癌旁相对正常乳腺组织,用免疫组织化学方法对不同乳腺组织标本进行检测.结果 Bcl-2在相对正常乳腺组织、非浸润性乳腺癌组织、浸润性乳腺癌组织中有不同程度的表达,其强阳性表达率分别为19.0%、41.7%、55.5%;p53在相对正常乳腺组织、非浸润性乳腺癌组织、浸润性乳腺癌组织中有不同程度的表达,其强阳性表达率分别为0%、50.0%、66.6%;而Bcl-2与p53表达之间存在显著相关性.结论 Bcl-2蛋白在乳腺癌组织中高表达与肿瘤的浸润有关;p53在乳腺癌组织中的过度表达,可能抑制乳腺癌细胞的凋亡发生,促进肿瘤的生长,与乳腺癌进展有关.p53及Bcl-2基因在乳腺癌发生发展过程中发挥着既独立又协同的作用.     

Identification of a novel human papillomavirus (HPV97) related to HPV18 and HPV45

Human papillomavirus (HPV) type 97 was identified and the genome was cloned from cervicovaginal cells of a Costa Rican woman with a normal Pap smear. The HPV97 L1 open reading frame (ORF) was most closely related to HPV45 (84% identity) and HPV18 (79% identity), placing it into the high-risk alpha7 species. Ectopic expression of the HPV97 E6 and E7 proteins significantly decreased steady state p53 and pRb levels using an in vitro cotransfection assay, respectively. These data suggest that HPV97 shares a most recent common ancestor with HPV18 and HPV45 and should be evaluated in cancer specimens from different geographic populations.     

乳腺癌及其癌前病变中细胞凋亡与p53、bcl-2蛋白的表达

目的：通过观察乳腺癌及其癌前病变中细胞凋亡调控基因ｐ５３、ｂｃｌ－２的表达,探讨细胞凋亡与凋亡调控基因在乳腺组织恶性转化进程中的作用。方法：利用ＤＮＡ缺口末端标记技术和免疫组织化学染色,原位观察３１例乳腺癌,２０例乳腺不典型增生和２０例乳腺单纯性增生中细胞凋亡和ｐ５３、ｂｃｌ－２蛋白的表达,以８例正常乳腺组织作为对照。结果：乳腺不典型增生和单纯性增生中细胞凋亡指数显著高于乳腺癌及正常乳腺组织（ｐ〉     

Human papillomavirus infection and p53 nuclear overexpression in anal canal carcinoma.

The product of HPV E6 and E7 genes is able to inactivate both the p53 and pRb proteins. The aim of this study was to evaluate the correlation among anal HPV infection and nuclear p53 overexpression. The Authors evaluated HPV DNA by PCR and p53 nuclear expression by immunohistochemistry in 12 cloacogenic and 6 squamocellular carcinoma. HPV DNA was detected in 71.4% of the squamocellular tumors and in 57.1% of the cloacogenic tumors. In squamocellular tumors HPV types 31-33 and 16 were found; in cloacogenic tumors type 16 alone was detected. Nuclear accumulation of p53 was found to be associated with the presence of HPV. There was no significant difference in parietal infiltration, lymph nodes involvement and prognosis between HPV+p53+ patients and HPV-p53- patients. Tumor aggressiveness is likely to be enhanced by factors other than HPV infection and p53 overexpression.     

Overexpression of Bcl-2 in squamous cell carcinoma of the larynx: a marker of radioresistance

Squamous cell carcinoma of the larynx can be treated using radiotherapy or surgery, either alone or in combination. Radiotherapy is preferred for early-stage tumours, as it spares the larynx and therefore preserves speech and swallowing. Unfortunately, approximately 15% of tumours treated this way will prove to be radioresistant, as manifest by tumour recurrence within the original radiotherapy field over the ensuing 12 months. By causing extensive DNA damage, radiotherapy aims to induce apoptosis and tumour regression. Our hypothesis was that defects in the mechanisms that recognise DNA damage, induce cell cycle arrest or control apoptosis, either alone or in combination, may be responsible for radioresistance. We therefore undertook an immunohistochemic analysis of pretreatment biopsies of radioresistant (n = 8) and radiosensitive (n = 13) laryngeal tumours. To minimise the impact of confounding factors, strict inclusion criteria were observed; all tumours were of the glottic subsite and all recurrences developed within 12 months of radiotherapy at the site of the original tumour. The expression of key proteins involved in DNA damage recognition (p53), cell cycle arrest (ATM, p16 and p21/WAF1) and apoptosis (Bcl-2 and BAX) were studied. Ki-67 was also assessed as a marker of cell proliferation to exclude low mitotic rate as a cause of radioresistance. A statistically significant correlation was observed between overexpression of Bcl-2 and radioresistance (p = 0.003, Fisher's exact test). We hypothesise that overexpression of the anti-apoptotic protein Bcl-2 allows tumour cells with extensive radiation-induced DNA damage to continue proliferating; the absence of an appropriate apoptotic response manifests clinically as radioresistance.     

Alterations of p53 and Bcl-2 protein expression in the laryngeal intraepithelial neoplasia

BACKGROUND: The squamous cell carcinoma of the larynx (SCC) is a common head and neck malignancy. I hypothesize that the development of laryngeal intraepithelial neoplasia (LIN) involves alterations of tumor suppressor genes (p53) and protooncogenes (Bcl-2). METHODS: To test this hypothesis, 40 vocal cord biopsy specimens were examined for p53 and Bcl-2 protein expression using immunoperoxidase staining methods and mouse monoclonal antibodies. RESULTS: The lesions appeared as localized , flat or papillary areas with white (leukoplakic) red (erythroplakic), or gray appearance. Histologically, the lesions entailed variable associations of mild (LIN I), moderate (LIN II), sever dysplasia (LIN III or in situ carcinoma) and superficially invasive SCC. As compared to the normal mucosa, the average weighted immunoreactivity scores for p53 and Bcl-2 proteins showed significant upregulation with the transitions from LIN I to LIN II to LIN III to superficially invasive SCC , respectively (0.0 +/- 0.0, 0.0 +/- 0.0, 1.8 +/- 0.8, 2.3 +/- 0.8, 5.8 +/- 3.2, p = 0.00 for p53 ) and (4.4 +/- 0.4, 4.0 +/- 0.8, 6.0 +/- 2.0, 9.6 +/- 1.6 and 10.7+/- 1.3, p = 0.00 for Bcl-2). There were insignificant positive correlation between p53 and both Bcl-2 (r = +0.8, p>0.13) protein expression. CONCLUSIONS: Alterations of the p53 and Bcl-2 proteins occur during the development of SCC.