Expression of matrix metalloproteinase (MMP)-7 and MMP-13 and loss of MMP-19 and p16 are associated with malignant progression in chronic wounds

BACKGROUND

The risk of squamous cell carcinoma (SCC) is significantly increased in chronic leg ulcers. Very little is known about the molecular pathogenesis of these tumours, which are often undiagnosed for a long time. As matrix metalloproteinases (MMPs) are implicated at all stages of tumorigenesis, we investigated whether the pattern of epithelial MMP expression can predict development of SCC from pseudoepitheliomatous hyperplasia of chronic wounds.

METHODS

Samples from nine patients with SCCs that had arisen in chronic wounds and 31 with venous leg ulcers were studied using immunohistochemistry for MMP-7, MMP-8, MMP-9, MMP-13, MMP-19 and the tumour suppressor p16. In situ hybridization was performed for MMP-1, MMP-3, MMP-7, MMP-12 and MMP-13.

RESULTS

MMP-7 was expressed by malignantly transformed epithelium, while it was absent from chronic wounds. MMP-9 was detected in the epithelium in both SCCs and chronic wounds. Epithelial MMP-13 expression was strong in SCC, but was absent in chronic wounds. MMP-12 was expressed in the epithelium in two SCCs, while macrophages were positive in chronic wounds. MMP-19 was induced in proliferating epithelium of wounds, but was absent from invasive areas of SCC. p16 was expressed by keratinocytes in half of the chronic wounds and at superficial margins of SCCs, while invasive areas were negative.

CONCLUSIONS

Our results suggest that epithelial expression of MMP-7, MMP-12 and MMP-13, but not that of MMP-1, MMP-3, MMP-8, MMP-9 and MMP-10, in chronic wounds provides a diagnostic clue for distinguishing SCCs from nonmalignant wounds. The loss of MMP-19 and p16 from the epithelium could aid in making the differential diagnosis between well-differentiated SCCs and nonmalignant chronic wounds.

Expression of p21WAF1/CIP1, p53, bcl-2 and Ki-67 in venous leg ulcers with and without squamous cell carcinoma

In order to gain understanding of the cellular mechanisms of malignant transformation in chronic venous leg ulcers, we analysed by immunohistochemistry the presence of p21, p53, bcl-2 and Ki-67 in ulcers with and without squamous cell carcinoma. The material consisted of 41 archived histopathological samples from 33 patients with chronic venous leg ulcers and 28 samples from 21 patients suffering from squamous cell carcinoma in chronic venous leg ulcers. All samples derived from the chronic ulcers were negative for p53, p21 and bcl-2. Cells positive for Ki-67 were seen in certain ulcer areas. In the cancers, 14 samples showed immunopositivity for p53 and 22 samples were positive for p21, with expression mainly in the suprabasal layer. Expression of p21 seemed independent of p53. None of the samples was bcl-2-positive. Ki-67 was positive with basal expression in 16/28 of the tumour samples, 15 of which also expressed p21. There was no perilesional p53 or p21 activity in the cancer samples. The results regarding perilesional expression are different from those reported in UV-induced squamous cell carcinomas and probably reflect a different carcinogen.

Venous leg ulcers and squamous cell carcinoma: a large-scale epidemiological study

In order to obtain a precise estimate of the relative risk of squamous cell carcinoma (SCC) in venous leg ulcers, we matched 10,913 patients with the diagnosis venous leg ulcer from the Swedish Inpatient Registry with registrations of SCC of the lower limb recorded by the Swedish Cancer Registry, and found 33 cases of non-melanoma skin cancer. After scrutinizing the pathology and case records, 17 cases of SCC were considered as being certainly secondary to venous leg ulcers, whereas in six cases of remitting/relapsing ulcers the connection was probable. The relative risk calculated on 17 cases was 5.80 (95% confidence interval = 3.08-9.29). The median duration of the ulcer before the diagnosis of cancer was 25 years. The mean follow-up time of the cohort was 8.5 years. We conclude that SCC is a complication of chronic venous leg ulcers, although the absolute risk is very small.

Leg ulcers and squamous cell carcinoma. An epidemiological study and a review of the literature

There has been concern about the possible risk of malignification of venous leg ulcers. To investigate the incidence of squamous cell carcinoma in venous ulcers, data on 1,170 patients with venous leg ulcers and 511 patients with other types of non-traumatic ulcers were matched with corresponding data from the Swedish Cancer Registry to determine the incidence of squamous cell carcinoma in these patients. Mean follow-up time was 8.3 years. Seven cases of squamous cell cancer were observed, while the expected number was 10.56 (relative risk = 0.66; 95% confidence interval = 0.27 to 1.36). However, four of the observed cancers were located on the lower leg in venous ulcers, the expected number being 0.68 (relative risk = 5.89; 95% confidence interval = 1.60 to 15.08). This indicates that a certain alertness is necessary when treating this common disease. The literature on cancer in venous ulcers, where 152 cases of squamous cell carcinoma in venous ulcers are reported, is reviewed.