Prolonged response to antisense cyclin D1 in a human squamous cancer xenograft model

Local recurrence of squamous cell cancer (SCC) causes high morbidity and is often readily accessible, making such patients potential candidates for ge ne therapy. Cyclin Df (CD1), critical in the G(1)-S transition in the cell cycle, is amplified in 20-50% and overexpressed in up to 80% of head and ne ck SCC, Our earlier studies indicated that CD1 expression increased with pr ogression from low grade to high grade dysplasia, and that treatment of est ablished tumors Kith antisense cyclin D1 (AS-cyclin D1) led to tumor regres sion during a one week evaluation period. We hypothesized that: I) CD1 expr ession increases with disease progression to advanced SCC, and 2) AS-cyclin Df therapy would lead to prolonged tumor regression in a xenograft model o f human SCC, CD1 expression, evaluated by immunostain in 30 stage III/IV he ad and neck SCC, increased in the basal layer from normal-dysplasia (P = 0. 06) and from dysplasia-carcinoma (P = 0.004), In the germinative layer CD1 expression increased from dysplasia-carcinoma (P = 0.002) but not from norm al-dysplasia, Western blotting of eight SCC and two transformed keratinocyt e cell lines demonstrated CD1 overexpression in 8/10 (80%) Lines. An 11th c ell Line (A431) had previously been shown to overexpress cyclin D1, 8/9 (89 %) cell lines overexpressing CD1 formed tumors in immunodeficient mice, whe reas 0/2 cell lines without CD1 overexpression formed a tumor, Three establ ished SCCs, one fast growing, one with moderate growth rate with CD1 overex pression and one slow growing (without increased CD1), shrank significantly for 2-4 weeks after AS-cyclin D1 treatment, while tumors transduced with c ontrol vector grew. Cyclin D1 expression increases in frequency with diseas e progression, and antisense cyclin Df was effective In a xenograft model o f human cancer, independent of tumor growth rate.