Chemopreventive agents induce a senescence-like phenotype in rat mammary tumours.

Terminal replicative senescence (TRS) is a physiological process associated with terminal differentiation, shortening of the telomere, and lack of proliferative activity. Immortalised and tumour cells have lost their differentiation potential and the ability to develop a senescence phenotype. Recently, others and we [11] have observed that some antitumour agents and radiation induce a senescence-like phenotype (SLP) in human immortalized and tumour cell lines. The main purpose of this study was to identify senescence-like cells (SLC) in mammary tumours of rats and assess whether chemopreventive agents that have been used for the prevention and/or treatment of breast cancer can induce a SLP in tumour cells. Sprague-Dawley rats with N-methyl-N-nitrosourea (MNU)-induced mammary tumours were randomised and treated with tamoxifen, vorozole, 4-(hydroxyphenyl)retinamide (4-HPR), or 9-cis-retinoic acid (9cRA). The SLC in mammary tumours were identified and characterised by: (a) SA-beta-Gal staining method, which has been considered specific for human cells in TRS (b) staining for lipofuscin, which, although not specific, accumulates in the cytoplasm of cells in senescence; (c) lack of 5-Bromodeoxyuridine (BrdU) labelling after continuous (7 days) infusion of BrdU via osmotic pumps; (d) 90 degrees side light scatter (9OLS) as evaluated by flow cytometry; and (e) decreased telomerase activity. We found that in control tumours, SA-beta-Gal-positive cells were rare (below 1.0%) among the tumour cells, stroma fibroblast, myoepithelial and endothelial cells. SA-beta-Gal-positive cells increased significantly in the tumours treated with chemopreventive agents and this was associated with a lack of proliferative activity, increased cell granularity, lipofuscin accumulation, and decreased telomerase activity. Thus, in this study we provide for the first time evidence that cells in replicative senescence are present in mammary tumours of rats and that chemopreventive agents can suppress tumor growth by a novel cellular mechanism, inducing a SLP in the tumor cells.

Molecular prognostic markers in intermediate-thickness cutaneous malignant melanoma.

BACKGROUND: The limitations of morphologic criteria alone in determining the prognosis for a patient with a particular intermediate-thickness primary melanoma have prompted efforts to identify other markers. METHODS: In this study, the authors analyzed expression of p53, beta1 integrin, and beta3 integrin in primary tumors from 111 patients with intermediate-thickness malignant melanoma. RESULTS: Eighty-nine (80%) had detectable p53 protein, 58 (52%) expressed beta1 integrin, and 71 (64%) expressed beta3 integrin. Patients with beta3 positive melanomas were more likely to die of their disease (32 of 71 patients, 45%) than those with beta3 negative tumors (3 of 40 patients, 8%) (P < 0.0001). The number of involved lymph nodes, Clark's level, beta1 integrin expression, thickness, and mitotic rate also had prognostic significance. beta3 integrin was associated with subsequent lung metastases and beta1 integrin with lymph node involvement. CONCLUSIONS: Integrin expression, along with histopathologic criteria, is a prognostic marker for intermediate-thickness malignant melanoma and may indicate the site of subsequent metastasis. These observations may have clinical utility and suggest areas for future investigation.

Beta 1 integrin expression: a marker of lymphatic metastases in cutaneous malignant melanoma.

BACKGROUND: Experimental evidence suggests that integrins are key regulators of the development of melanoma metastases, influencing both the likelihood and site of metastases. Whereas effective treatment of cutaneous melanoma remains surgical, elective lymph node dissection (ELND) is controversial. The present study was designed to investigate the relationship between integrin expression by a given primary melanoma and occult regional lymph node metastases. MATERIALS AND METHODS: We studied beta 1 integrin expression, by quantitative immunohistochemistry using an image analyzer, in the primary melanomas of 90 ELND patients. RESULTS: beta 1 integrin was expressed in > or = 10% of the primary tumor in 92% of cases eith lymph node involvement versus 9% of node negative cases (p < 0.001). CONCLUSIONS: Our data demonstrate that quantitative immunohistochemistry for beta 1 integrin expression in primary melanomas can identify patients likely to have occult lymph node metastases. This suggests that beta 1 integrins play a role in the lymphatic dissemination of cutaneous melanoma.

Beta 1 integrin expression in malignant melanoma predicts occult lymph node metastases.

BACKGROUND: Elective lymph node dissection for malignant melanoma is still controversial. Experimental studies suggest that differential expression, activation, or both of beta1 integrins facilitate melanoma metastases. However, the clinical significance of beta1 integrin expression in human melanoma is unclear. METHODS: We examined primary cutaneous melanomas from 76 patients undergoing elective lymph mode dissection. We quantified the percentage of tumor area stained by beta1 integrin antibody with an image analyzer. RESULTS: beta1 integrin was expressed in all 23 primary tumors from patients with pathologically positive lymph nodes (LNs) but in only 14 (26%) of 53 cases with pathologically negative nodes (p < 0.001). No patients with beta1 integrin-negative tumors had LN involvement, whereas 23 (62%) of 37 patients with beta1 integrin-positive tumors had LN metastases (p < 0.001). Furthermore, 21 (91%) of 23 cases with LN metastases but only 4 (8%) of 53 cases without had beta1 integrin staining of 10% or more of tumor area (p < 0.001). CONCLUSIONS: Our study is the first to show a correlation between expression of a molecular marker in the primary cutaneous melanoma and likelihood of regional LN metastases. beta1 immunostaining of 10% or more of tumor area reliably predicts patients most likely to harbor occult LN metastases and likely to benefit from ELND.