Human papillomavirus and p53 protein immunoreactivity in condylomata acuminatum and squamous cell carcinoma of penis

Xin-Hua ZHANG, Gui-Qin SUN, Yu YANG, Tai-He ZHANG

Department of Pathology, General Hospital of Nanjing Command, PLA, Nanjing 210002, China

Asian J Androl  2001 Mar; 3:  75-77

Keywords: condylomata acuminata; penile diseases; carcinoma; HPV; protein p53

Abstract

Aim: To determine the immunoreactive pattern of human papillomavirus (HPV) antigen and p53 protein in condylomata acuminatum (CA) and squamous cell carcinoma (SCC) of penis. Methods: Immunohistochemistry for HPV and p53 were performed in 40 specimens of formalin fixed, paraffin  embedded tissues using a polyclonal (rabbit) antibody against HPV and a monoclonal (mouse) antibody against human p53 protein. Twenty one cases of CA and nineteen cases of SCC were examined. Results: HPV antigen was detected in all 21 CA and 2 penile SCC. p53 protein overexpression was observed in 12 of 19 (63%) SCC in which 6 cases were strong positive. Five of 21 CA (24%) showed low-grade p53 protein overexpression. Conclusion: CA is related to HPV infection and some cases show p53 protein low-grade overexpression. In contrast, p53 protein overexpression is common in penile SCC, which is seldom related to HPV infection.

1 Introduction

2 Materials and methods

Twenty one CA and nineteen SCC formalin fixed and paraffin embedded specimens of penile tissues were prepared. The histological diagnosis was confirmed by viewing the haematoxylin and eosin stained sections. Immunohistochemistry was performed using a standard labeled streptavidin method. The presence of HPV infection and overexpression of p53 were assessed by using rabbit anti-human papillomavirus (RAB-0144) and mouse anti-human p53 protein (DO-7).

The presence or absence of staining and the number of nuclei with a positive reaction were observed. For HPV, it was assessed as positive reaction regardless of the number of positive nuclei. For p53 protein, less than 10% inclusive positive nuclei was considered negative, 11-50% as positive, and >50% as highly positive.

 3 Results

3.1 Presence of HPV

HPV infection was detected in all 21 CA cases with a 100% positive rate (Figure 1). In 19 cases of penile SCC, HPV antigen was detected in two cases (a 10% positive rate).

Fig 1. HPV positive reaction in CA. Immunostaining (S-P method).

3.2 Expression of p53 protein in the specimens

P53 protein overexpression was detected in 5 of 21 CA (24%). The positive reaction was seen in the nuclei of the basal and supra-basal layers of the epithelium, with mild to moderate nuclear atypia, but no one was strongly positive, i.e., the number of positive nuclei was below 50%.

Of the 19 cases of penile SCC, p53 protein overexpression was observed in 12 cases (63%), of which 6 (32%) were strongly positive. Seven of the 12 p53 positive carcinoma were keratinizing squamous carcinoma, and five were low to moderate differentiated squamous carcinoma. The site of these p53 immunoreactive cells in penile SCC was not in conformity with the cellular differentiation or keratinization tendency, i.e., the nuclei of basal and supra-basal layer or poorly differentiated cells had much more and stronger positive reaction (Figure 2). In other words, fewer and fainter positive nuclei were seen in the superficial layer or marked keratinized malignant cells. The negative controls showed no staining.

A significant difference was found in p53 protein positive rate between CA and penile SCC (P<0.05) (Data not shown).

Fig 2. p53 protein positive reaction in penile SCC. Immunostaining (S-P method).

4 Discussion

Penile squamous cell carcinoma has been considered a disease of old men. Its etiology and carcinogenetic mechanism are largely unknown. There was a general agreement that circumcision performed in infancy gives almost 100% protection against the disease, while circumcision performed later in the life gives less protection. Secretion retained in the preputial sac appears to play an important role in the genesis of the penile cancer^[2]. However, a number of recent epidemiological studies have linked the penile carcinomas with the following risk factors: multiple sexual partners, a history of venereal warts, and cigarette smoking^[3]. In the current study, HPV antigen was detected in 2 of 19 penile SCC (10%) suggesting that HPV infection may have some association with the subsequent development of the penile cancer. Other investigators also showed a higher HPV infection rate in penile cancer. In one study using PCR, 15% (6/41) of the penile cancers had evidence of HPV infection and most of them had HPV type 16 or/and HPV18^[4]. An investigation in 53 Brazilian men with penile cancer showed that nearly half (49%) were HPV type 16 positive^[5].

Another important factor in the development of ano-genital carcinomas appears to be the presence of alterations in p53 activity. The current study showed that p53 protein overexpression was detected in 5 of 21 CA (24%). On the contrary, p53 overexpression is common in penile SCC. Approximately 63% of 19 penile SCC had p53 overexpression. Overexpression of p53 protein in tissues has generally been assumed to reflect p53 mutation, which could result in loss of suppressor function and induction of growth-promoting potential^[6]. Mutant p53 proteins have a longer half-life and accumulate in the cells. However, several reports suggest that p53 immunoreactivity does not correlate with mutation but may reflect the change in wild-type p53 from a suppressor to a promoter form during the cell growth response, or a longer halflife of the protein due to binding by another protein^[7,8]. Lam et al^[9] found p53 protein overexpression in 17 of 42 (40%) primary penile carcinomas. Positive p53 staining was identified only in the less differentiated tumor cells in the periphery of the tumor cell nests. Levi et al^[10] demonstrated p53 overexpression in 26% of 64 penile carcinomas. They also revealed point mutations in p53 exons 6 (1 case), 7 (1 case) and 8 (5 cases). Suzuki et al^[11] investigated p53 mutations in 13 Japanese penile cancers. Neither HPV-detected nor HPV-undetected tissues showed alterations in exon 4-9 of p53 gene. The present study indicated that p53 overexpression was a frequent finding in Chinese penile carcinomas. Nevertheless, two HPV-positive penile carcinomas had no p53 protein overexpression, and another five cases showed neither p53 overexpression nor HPV infection, indicating that one-third of the penile squamous cell carcinomas might arise through a mechanism independent of p53 inactivation or mutation.

References

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Correspondence to: Dr. Xin-Hua ZHANG, Department of Pathology, General Hospital of Nanjing Command, PLA, Nanjing 210002, China.
Tel: +86-25-338 7871 Ext. 58192
Received 2000-04-21     Accepted 2001-02-28