Evidence that expression of a mutated p53 gene attenuates apoptotic cell death in human gastric intestinal-type carcinomas in vivo

Hyperthermia induces translocation of apoptosis-inducing factor (AIF) and apoptosis in human glioma cell lines

In the hyperthermal treatment, the wild type (wt) p53 plays an important role in apoptosis induction in the tumor cells. In human gliomas, p53 frequently has some form of mutation. The mutant type (mt) p53 does not work properly as a tumor suppressor and this may result in poor responses during treatment. We investigated the relationship between apoptosis-inducing factor (AIF) and apoptosis under various thermal conditions (43, 45, and 47 degrees C for 1 h) using four p53-wild or -mutant human glioma cell lines (A172, T98G, U251MG, and YKG-1). AIF translocation from the mitochondria to the nucleus under hyperthermal conditions was demonstrated by confocal laser microscopy. The percentage of AIF-positive nuclei increased significantly in comparison with the control in all cell lines and in all temperature groups except for YKG-1 at 47 degrees C. Immunoblot analyses of the nuclear fraction of each cell line revealed temperature-dependent increases in AIF. A simultaneous release of cytochrome c from the mitochondria to the cytosol was noted. A flow cytometric analysis showed that apoptosis induction occurred more often in a temperature-dependent manner in the 45 and 47 degrees C groups than in the control group. These findings indicate that the hyperthermal conditions can lead to AIF translocation and apoptotic cell death in the p53-mutant human glioma cells. The present report is the first description of AIF-induced apoptosis in hyperthermia.

DNA integrity as a potential marker for stool-based detection of colorectal cancer

BACKGROUND

Molecular genetic analysis of DNA in patient stools has been proposed for screening of colorectal cancer (CRC). Because nonapoptotic cells shed from tumors may contain DNA that is less degraded than DNA fragments from healthy colonic mucosa, our aim was to show that DNA fragments isolated from stools of patients with CRC had higher integrity than DNA isolated from stools of patients with healthy colonic mucosa.

METHODS

We purified DNA from the stools of a colonoscopy-negative control group and patients with CRC and examined the relationship between long DNA fragments and clinical status by determining stool DNA integrity, using oligonucleotide-based hybrid captures with specific target sequences in increasingly long PCR reactions (200 bp, 400 bp, 800 bp, 1.3 kb, 1.8 kb, 24 kb). DNA fragments obtained from CRC patients were compared with fragments obtained from colonoscopy-negative individuals for length and/or integrity.

RESULTS

DNA fragments isolated from CRC patients were of higher molecular weight (>18 bands detected of a total of 24 possible bands) than fragments isolated from fecal DNA of the colonoscopy-negative control group.

CONCLUSIONS

The presence of long DNA fragments in stool is associated with CRC and may be related to disease-associated differences in the regulation of proliferation and apoptosis. An assay of fecal DNA integrity may be a useful biomarker for the detection of CRC.

Hyperthermic induction of apoptosis in malignant fibrous histiocytoma cells: possible involvement of a p53-independent pathway in the induction of bax gene

We have previously reported the unique heat sensitivity of a cell line of malignant fibrous histiocytoma cells, the MFH-2NR cell line. In the present study, treatment of MFH-2NR cells, at 43 degrees C for 1 h evoked typical apoptosis in these cells, which showed characteristic morphological changes, such as internucleosomal DNA fragmentation (DNA ladders), cell shrinkage, and chromatin condensation. Under these conditions, we examined p53 and bax protein levels, and p53 and bax mRNA expression to assess the potential relationship between these two proteins for the induction of apoptosis. The p53 protein, which is usually detected in trace amounts in normal cells, was highly expressed in untreated MFH-2NR cells, and the level did not increase after heat treatment, whereas the bax protein level increased from 30 min after the treatment. No change in p53 mRNA was found, but a transient increase in bax mRNA, peaking at 30 min, was detected by Northern blotting. DNA sequence analysis of the p53 gene from MFH-2NR cells demonstrated a GGG right arrow GAG homozygous point mutation in codon 242 of exon 6. These results suggest that the expression of bax protein and mRNA was augmented by a p53-independent pathway in the hyperthermia-induced apoptosis of MFH-2NR cells.

Apoptotic tumor-cell death in response to cell proliferation is influenced by p53 status in resected non-small cell lung cancer

To evaluate the influence of p53 status on postoperative survival and incidence of apoptosis (apoptotic index, AI) in non-small cell lung cancer (NSCLC), a total of 185 pathologic stage I patients were retrospectively analyzed. It was demonstrated by univariate and multivariate analyses that aberrant expression of p53 was a significant factor to predict a poor prognosis, which was caused by a significantly higher proliferative index (PI) in tumor with aberrant expression of p53 (52.7%) than that in tumor without aberrant expression of p53 (37.9%, P < 0.001). In addition, for tumor without aberrant expression of p53, mean AIs of the lowest-, the lower-, the higher-, and the highest-PI groups were 12.6, 12.9, 31.3, and 35.1, respectively, showing that incidence of apoptosis was markedly increased in response to cell proliferation (P = 0.002). In contrast, for tumor with aberrant expression of p53, no increase in incidence of apoptosis in response to cell proliferation was documented. These results clearly demonstrated that active cell proliferation and reduced apoptotic cell death in response to cell proliferation resulted in the poor postoperative prognosis in tumor with aberrant expression of p53.

Expression of nitric oxide synthase, cyclooxygenase, and p53 in different stages of human gastric cancer

The present study evaluated the significance of nitric oxide synthase (NOS), cyclooxygenase (COX) expression and p53 status in 55 patients with gastric adenocarcinoma and relationship of these molecular markers to tumor characteristics and metastatic potential. Immunohistochemical technique was used to identify the cellular location and distribution of the enzymes in the specific cells of gastric tumors. In gastric cancer tissue, the expression of inducible enzymes, iNOS and COX-2, increased significantly with increasing tumor stage (P=0.015, P=0.001, respectively), size (P=0.025, P=0.001, respectively) and the presence of metastases (P=0.002, P=0.015, respectively). The expression of constitutive enzymes, ecNOS and COX-1, followed the opposite pattern. COX-1 was significantly reduced in advanced gastric tumors (P=0.007) and tumors larger than 5 cm (P=0.007). Reduced expression of ecNOS was also observed in advanced gastric tumors; however, this did not reach statistical significance. 53% of gastric tumors showed accumulation of p53. This was significantly higher in advanced tumors (P=0.004), larger than 5 cm (P=0.015) with metastases (P<0.001). Gastric tumors positive for accumulation of p53 had significantly stronger expression of iNOS (P=0.018) and COX-2 (P=0.01) enzymes than tumors negative for this nucleophosphoprotein. We conclude, that tumor-associated nitric oxide production, as well as COX-2 overexpression, may promote gastric cancer progression by providing a selective growth advantage to tumor cells with non-functioning p53.

Thymidine phosphorylase expression causes both the increase of intratumoral microvessels and decrease of apoptosis in human esophageal carcinomas

Thymidine phosphorylase (dThdPase)/platelet-derived endothelial cell growth factor, is expressed at higher levels in tumor tissues compared to the adjacent normal tissues in a variety of human carcinomas. The higher expression is associated with an increase of intratumoral microvessel density (IMVD) and an unfavorable patient prognosis. We examined the role of dThdPase in apoptosis, IMVD, P53 expression and patient prognosis of human stages II and III esophageal squamous cell carcinomas (SCC). dThdPase expression was noted in 52 of the 78 esophageal SCC (66.7%), regardless of tumor stages and histologic grades. Mean IMVD was 117.9 +/- 32.6 in the dThdPase-positive cases and 103.1 +/- 21.5 in the dThdPase-negative cases, the value being significantly higher in the former (P < 0.05). Similarly, median (range) apoptotic index (AI: percentage of apoptotic cells) was significantly lower in the dThdPase-positive SCC, 1.8 (0.4-6.5), than in the dThdPase-negative SCC, 3.7 (0.6-7.0) (P < 0.01). AI and IMVD showed a significant inverse correlation (r = - 0.31, P = 0.005). There was also no significant difference in the frequency of P53 expression between the dThdPase-positive SCC and the negative SCC. No statistical difference was noted regarding the postoperative survival rate between the dThdPase-positive and the negative SCC. Although dThdPase expression was not associated with patient prognosis, the expression provided an advantage for tumor growth of human esophageal SCC, not only by increasing the intratumoral microvessels, but also attenuation of apoptosis, which might occur via a p53 gene-independent pathway.

Apoptosis in gastric epithelium induced by Helicobacter pylori infection: implications in gastric carcinogenesis

OBJECTIVES

Helicobacter pylori is an identified carcinogen for gastric cancer, however, the underlying mechanisms remain to be defined. In this review, we sought to elucidate the role of apoptosis in gastric carcinogenesis, to determine the influence of H. pylori infection on apoptosis, and finally to provide insights into the mechanisms by which H. pylori may lead to gastric carcinogenesis.

METHODS

A broad-based MEDLINE and Current Contents literature search was performed to identify relevant publications between 1966 and March 2000 addressing H. pylori infection, apoptosis, cell proliferation, gastric carcinoma, oncogenes, and tumor suppressor genes, as well as the products of these genes. Abstracts from recent major conferences that provided adequate additional data were also included.

RESULTS

Apoptotic cells are rare in the glandular neck region (the generative cell zone) of normal gastric mucosa. With progression of atrophic gastritis, the generative cell zone shifts downward and a relatively large number of apoptotic cells occur. In intestinalized glands, both apoptotic cells and proliferative cells are present in deeper portions of the glands, corresponding to the generative zone. A higher frequency of apoptosis has been observed in gastric dysplasia than in coexisting gastric carcinomas, whereas the number of proliferative cells is significantly higher in gastric carcinoma than in dysplasia. Upregulation of oncogene bcl-2 in premalignant lesions and "downregulation" of the gene after malignant change is probably a common event. Accumulation of p53 protein is first detected in dysplasia, although mutation of the pS3 gene may occur in intestinal metaplasia. H. pylori infection induces apoptosis in gastric epithelial cells, which returns to normal after eradication of the infection. Numerous molecules produced by H. pylori including cytotoxin (VacA), lipopolysaccharide, monochloramine, and nitric oxide may directly induce apoptosis. Moreover, H. pylori-stimulated host inflammatory/immune responses lead to release of a large amount of cytokines. Cytokines produced by type 1 T helper cells, such as TNF-alpha and IFN-gamma, markedly potentiate apoptosis. Gastric cell proliferation is significantly higher in patients with H. pylori infection than in normal controls, and eradication of the infection leads to a reduction in cell proliferation. Apoptosis and cell proliferation are also increased in precancerous lesions such as gastric atrophy, intestinal metaplasia, and dysplasia in the presence of H. pylori infection. However, H. pylori-induced apoptosis may no longer be cell cycle-dependent in these lesions because of the occurrence of alterations and mutations of apoptosis-regulating genes, resulting in a loss of balance between apoptosis and cell proliferation.

CONCLUSIONS

It is hypothesized that H. pylori-induced apoptosis may play a key role in gastric carcinogenesis by increasing cell proliferation and/or resulting in gastric atrophy.

Ultrastructural and immunohistochemical analysis of cholangiocarcinoma in immunized Syrian golden hamsters infected with Opisthorchis viverrini and administered with dimethylnitrosamine

Utilizing the experimental model in Syrian golden hamsters, we explored the role of immunization in carcinogenesis. The animals, which were infected with liver flukes (Opisthorchis viverrini), and administered a subcarcinogenic dose of dimethylnitrosamine, developed cancer. Pre-immunizing with a crude somatic antigen did not reduce cancer development, but accelerated carcinogenesis. Histopathological analysis of the cancer tissues was done once at week 30 and again at week 39 using H and E staining, immunostaining for the p53 tumor suppressor phosphoprotein, and electron microscopy. Thirty weeks after immunization, the immunized hamsters developed tubular adenocarcinoma at a higher rate (71.43%) than the non-immunized group (20.00%). This rate (20.00%) increased to 63.64% by week 39. The small foci cancer in the non-immunized group decreased in frequency from 80.00% (at week 30) to 36.36% (by week 39), suggesting the small foci cancer progressed to tubular adenocarcinoma during the 9-week interval. Most of the observed tubular adenocarcinoma was well differentiated. Nearly all hamsters that tested positive for cancer also tested positive for p53 immunostaining in the epithelia of the small bile ducts. The positive reaction for p53-immunostaining was localized in the rough endoplasmic reticulum, Golgi apparatus and perinuclear membranes. The electron micrographs of these positive p53-immunostained cells showed characteristics of early cancer. The detection of p53 in early cancer development makes it a candidate as a tumor marker.

Preoperative treatment with tegafur suppositories enhances apoptosis and reduces the intratumoral microvessel density of human colorectal carcinoma

BACKGROUND

This study examined the effect of tegafur, a depot of 5-fluorouracil, in human colorectal carcinomas in terms of apoptosis, cell proliferation, and expression of p53 gene and angiogenesis-related molecules.

METHODS

A total of 32 patients with colorectal carcinoma were divided into 2 groups; 20 patients received tegafur suppositories (TS) at 1 g/day for 14 days before surgery, and 12 patients did not receive any chemotherapy. Surgically removed specimens were examined immunohistochemically for Ki-67, CD34, p53, p21, Bax, vascular endothelial growth factor (VEGF), and thymidine phosphorylase (dThdPase). Apoptotic tumor cells were visualized by the terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-digoxigenin nick-end labeling (TUNEL) procedure.

RESULTS

The mean percentage of apoptotic index (AI) was 6.9 +/- 1.2 in the 20 TS-treated tumors and 4.4 +/- 1.0 in the 12 nontreated tumors (P < 0.001). In contrast, the mean percentage of Ki-67 labeling index (KI) became significantly lower in the former group (P < 0.05). The frequency of p21 expression was significantly higher in the TS-treated group than in the nontreated group (P < 0.05), whereas no difference was detected in p53 and Bax expression between the two groups. The mean intratumoral microvessel density was 47.8 +/- 19.8 in the TS-treated tumors and 66.8 +/- 16.5 in the nontreated tumors (P < 0.01). The frequency of dThdPase expression, but not of VEGF expression, became significantly lower with the TS treatment. p53 expression did not correlate with AI, KI, IMV density, or the expression of VEGF, p21, or Bax, except for dThdPase, which was significantly higher in the 18 p53 positive tumors (P < 0.05).

CONCLUSIONS

Preoperative TS treatment enhances apoptosis and suppresses angiogenesis of colorectal carcinomas in a p53-independent manner.

Circulating p53 antibody in patients with colorectal cancer: relation to clinicopathologic features and survival

The presence of serum anti-p53 antibody has been reported to be associated with survival of patients with breast cancer, ovarian cancer, and hepatocellular carcinoma. To clarify prognostic significance of p53 antibody in colorectal cancer, serum p53 antibody was measured in patients with colorectal cancer. The 89 patients included 71 with colorectal cancer and 18 with colon polyp. An enzyme-linked immunosorbent assay was used to detect p53 antibodies in serum. Clinicopathological parameters such as age, sex, degree of differentiation of cancer, location of tumor, liver metastasis, stage classification, Dukes classification, CEA, CA19-9, and immunostaining of p53 and anti-p53 antibody were evaluated as prognostic factors of colorectal cancer. p53 antibody was positive in 18 of 71 (25%) with colorectal cancer, whereas it was positive in only 1 of 18 (6%) with colon polyp. The patients with p53 antibody had higher CEA and CA19-9 levels, higher positive rates of p53 protein expression in cancer cells, and higher liver metastasis rates. The p53 antibody positivity at stage classification I-IIIb/ Dukes classification A-C was significantly lower than that at stage classification IV/Dukes classification D. Overall survival in colorectal cancer patients with p53 antibody was significantly shorter than in those without p53 antibody. A Cox regression analysis showed that liver metastasis, stage classification, Dukes classification, CA19-9, and p53 antibody were significant prognostic factors in colorectal cancer. Serum anti-p53 antibody could serve as one of the prognostic factors in patients with colorectal cancer.

Circulating p53 antibody in patients with colorectal cancer: relation to clinicopathologic features and survival

The presence of serum anti-p53 antibody has been reported to be associated with survival of patients with breast cancer, ovarian cancer, and hepatocellular carcinoma. To clarify prognostic significance of p53 antibody in colorectal cancer, serum p53 antibody was measured in patients with colorectal cancer. The 89 patients included 71 with colorectal cancer and 18 with colon polyp. An enzyme-linked immunosorbent assay was used to detect p53 antibodies in serum. Clinicopathological parameters such as age, sex, degree of differentiation of cancer, location of tumor, liver metastasis, stage classification, Dukes classification, CEA, CA19-9, and immunostaining of p53 and anti-p53 antibody were evaluated as prognostic factors of colorectal cancer. p53 antibody was positive in 18 of 71 (25%) with colorectal cancer, whereas it was positive in only 1 of 18 (6%) with colon polyp. The patients with p53 antibody had higher CEA and CA19-9 levels, higher positive rates of p53 protein expression in cancer cells, and higher liver metastasis rates. The p53 antibody positivity at stage classification I-IIIb/ Dukes classification A-C was significantly lower than that at stage classification IV/Dukes classification D. Overall survival in colorectal cancer patients with p53 antibody was significantly shorter than in those without p53 antibody. A Cox regression analysis showed that liver metastasis, stage classification, Dukes classification, CA19-9, and p53 antibody were significant prognostic factors in colorectal cancer. Serum anti-p53 antibody could serve as one of the prognostic factors in patients with colorectal cancer.

Prognostic significance of apoptotic index in completely resected non-small-cell lung cancer

PURPOSE

To evaluate the significance of apoptotic index (AI) as a prognostic factor after surgery for non-small-cell lung cancer (NSCLC).

PATIENTS AND METHODS

A total of 236 patients who underwent surgery for previously untreated pathologic stage I to IIIa NSCLC between 1985 and 1990 were reviewed. AI was defined as the number of apoptotic cells, detected by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end-labeling, per 1,000 tumor cells. Proliferative index (PI) and aberrant p53 expression were also evaluated immunohistochemically.

RESULTS

The 5-year survival rate for the lowest-AI group (AI < 5.0) was 74.7%; those for the lower-AI group (5.0 < or = AI < 11.0) and the higher-AI group (11.0 < or = AI < 25.0) were 51.6% and 57.8%, respectively. These survival rates were significantly lower than that of the lowest-AI group (P =.021 and P =.043, respectively). The highest-AI group (25.0 < or = AI), however, showed the most favorable prognosis, with a 5-year survival rate of 83.2%. Multivariate analysis confirmed that a moderate AI (5.0 < or = AI < 11.0 or 11.0 < or = AI < 25.0) was a significant factor to predict poor prognosis. The PIs for the lowest-, the lower-, the higher-, and the highest-AI groups were 32.3%, 48.0%, 54.3%, and 50.7%, respectively. The lowest-AI group showed a favorable prognosis because of its low PI, whereas the lower- and the higher-AI groups had a poor prognosis caused by increased cancer-cell proliferation. The highest-AI group showed the most favorable prognosis because apoptotic cell death overcame cell proliferation. No significant correlation was observed between AI and aberrant p53 expression.

CONCLUSION

AI proved to be an independent prognostic factor in NSCLC.

Differential apoptosis by indomethacin in gastric epithelial cells through the constitutive expression of wild-type p53 and/or up-regulation of c-myc

Nonsteroidal anti-inflammatory drug (NSAID)-induced apoptosis is considered to be an important mechanism in the antineoplastic effects and damage produced by the drugs in the gastrointestinal tract. In this study, two different gastric cancer cell lines, MKN28 (mutant-type p53) and AGS (wild-type p53), were compared as to growth inhibition, apoptosis, and cell cycle and apoptosis-related gene expression in response to indomethacin treatment. Cell growth was measured by MTT (3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyl tetrazolium bromide) assay. Apoptosis was characterized by acridine orange staining and DNA fragmentation, and cell cycle kinetics by flow cytometry. The mRNA and protein levels of p53, p21waf1/cip1, and c-myc were determined by Northern and Western blotting. The results showed that indomethacin initiated growth inhibition and apoptosis in both cell lines without cell cycle shifting. AGS cells were more sensitive to growth inhibitory activity and apoptosis of indomethacin than MKN28 cells. In MKN28 cells, the levels of p53, p21waf1/cip1, and c-myc mRNA remained unchanged over the 24-hr treatment with indomethacin, but the p53 protein level was elevated after 4 hr. There was no change in the p21waf1/cip1 and c-myc protein levels in the MKN28 cells. In AGS cells, a progressive increase in c-myc mRNA and protein levels was noted, while p53 and p21waf1/cip1 remained unchanged. It can be concluded that wild-type p53 and/or up-regulation of c-myc is associated with indomethacin-mediated differential apoptosis in gastric epithelial cells.

Thymidine phosphorylase expression in human colorectal mucosa, adenoma and carcinoma: role of p53 expression

The enzyme, thymidine phosphorylase (dThdPase) is identical to platelet-derived endothelial cell growth factor (PD-ECGF), which acts as a potent angiogenic factor. The present study immunohistochemically examined the expression of dThdPase in human colorectal mucosa, adenomas and carcinomas, as well as six cultured colorectal carcinoma cell lines, in terms of intratumoral microvessel density (IMVD) and P53 expression. Thymidine phosphorylase was observed in lymphocytes, fibroblasts and macrophages, as well as smooth muscle cells and Schwann cells in the peripheral nerve fibers. The dThdPase-positive stromal cells apparently outnumbered the normal epithelial cells, adenoma and carcinoma cells with dThdPase. Weak but obvious cytoplasmic immunoreactivity was noted in a few normal colonic epithelia, predominantly the upper surface area, while a few adenoma cells showed weak nuclear immunostaining for dThdPase in six (24%) of the 25 colonic adenomas. Expression of dThdPase was noted in 33 (73.3%) of the 45 Dukes A and B, 14 (51.9%) of the 27 Dukes C and 14 (56.0%) of the 25 Dukes D carcinomas. The mean IMVD was 84.0 +/- 26.2 in the 36 dThdPase-negative carcinomas and 97.9 +/- 31.6 in the 61 dThdPase-positive carcinomas, the value being significantly higher in the latter group (P < 0.05). The frequency of dThdPase expression was significantly lower in the P53-negative carcinomas than in the positive carcinomas (P < 0.05). Western blot analysis showed the highest expression of dThdPase in LoVo carrying the wild-type p53 gene, followed by Colo201, Colo320, DLD-11 and WiDr carrying the mutated gene. These results indicate that: (i) the main source of dThdPase is stromal cells, including lymphocytes and macrophages in both colorectal normal and carcinoma tissues; (ii) dThdPase may take part in the induction of intratumoral microvessels, regardless of tumor stage; and (iii) expression might be modulated by not only P53 but also other molecules.

Pre-operative radio-chemotherapy enhances apoptotic cell death in oral squamous cell carcinoma

The effect of pre-operative radio-chemotherapy (RCT) has been examined in a total of 15 oral squamous cell carcinomas (SCCs), in terms of apoptosis (cell loss) and proliferation. All the patients received pre-operative radiation at a dosage of 30 or 40 Gy, as well as anticancer agents including tagaful (FT), 5-fluorouracil (5-FU), bleomycin (BLM) and peplomycin (PEP). Surgical specimens were obtained before and after RCT, and serial sections were prepared for immunohistochemistry for p53 oncoprotein and Ki-67 antigen, as well as for terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-biotin nick end labeling (TUNEL). TUNEL indices (TI; percentage of TUNEL-positive cells in the tumor cells) before and after RCT were 1.2+/-1.1 and 4.7+/-2.9 in the nine well-differentiated oral SCCs, and 1.0+/-0.7 and 3.9+/-2.1 in the six poorly differentiated SCCs, respectively. Similarly, Ki-67 indices (KI; percentage of Ki-67 antigen-positive cells in tumor cells) before and after RCT were 31.1+/-14.2 and 15.8+/-11.1 in the former, and 37.1+/-7.8 and 8.7+/- 13.4 in the latter, respectively. Thus, pre-operative RCT enhanced apoptotic cell death and abated proliferative activity significantly (P<0.05), regardless of histological differentiation. Enhancement of apoptosis was more prominent in the group treated with FT or 5-FU than with BLM or PEP. Oral SCC with >20% of nuclear p53-positive tumor cells was noted in six cases. Enhanced TI and abadement of KI did not differ among the p53-positive and -negative tumors.

Apoptosis and cellular proliferation in human epidermal squamous cell neoplasia

We examined cell loss (apoptosis) and proliferation in a histopathological spectrum of epidermal squamous cell neoplasia, including 11 cases of solar keratosis (SK), 18 Bowen's diseases (BD) and 19 invasive squamous cell carcinomas (SCC). Apoptotic and proliferative cells were determined by terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-digoxigenin nick end labeling (TUNEL) and by the detection of nuclear antigen Ki-67, respectively. Few apoptotic cells were observed in normal epidermis, while TUNEL index (TI; percentage of TUNEL-positive cells) was highest for SCCs, followed by BDs and SKs, in the order given. Although the mean Ki-67 index did not differ between SCCs and BDs, both disease types showed a significantly higher index than the SKs. Of SCCs, both TI and Ki-67 index values were significantly higher in poorly than in well differentiated carcinomas. TI was significantly higher in SCCs without P53 immunohistochemical expression than in SCCs with P53 expression, while TI and Ki-67 indices did not correlate with P53 expression in the SKs and BDs. These results suggest that apoptosis reflects not only cell loss, but also proliferative activity in the epidermal neoplastic lesions.