© 2 0 0 4 B J U I N T E R N A T I O N A L | 9 3 , 2 9 1 – 2 9 6 | doi:10.1111/j.1464-410X.2004.04604.x 291 Original Article CAVEOLIN-1 AND MICROVESSEL DENSITY IN RCC H.J. JOO et al. Increased expression of caveolin-1 and microvessel density correlates with metastasis and poor prognosis in clear cell renal cell carcinoma H.J. JOO, D.K. OH*, Y.S. KIM*, K.B. LEE and S.J. KIM* Departments of Pathology and *Urology, Ajou University School of Medicine, Suwon, Korea Accepted for publication 20 October 2003 RESULTS Eighteen patients had either synchronous or metachronous metastases and 11 died during the follow-up. Caveolin-1 intensity was significantly correlated with tumour size (P = 0.005), TNM stage (P = 0.028), M stage (P = 0.012), grade (P = 0.015), and metastasis (synchronous or metachronous; P < 0.001). The caveolin-1 proportion (P = 0.037) and MVD (P = 0.011) were significantly correlated with metastasis. MVD was correlated with caveolin-1 intensity (r = 0.385, P = 0.001) and caveolin-1 proportion (r = 0.388, P = 0.001). There was no difference in the expression of caveolin-1 and MVD between primary and metastatic sites. The survival of patients with higher caveolin-1 intensity was significantly worse than that of patients with lower caveolin-1 intensity. Multivariate analyses indicated that only M-stage was an independent prognostic factor for cancer- specific survival and caveolin-1 expression was not an independent factor. CONCLUSIONS Increased expression of caveolin-1 and MVD is associated with metastasis and a worse prognosis in clear cell RCC. Caveolin-1 expression is correlated with MVD. These results suggest that caveolin-1 may be important in the progression of clear cell RCC and angiogenesis may be affected by caveolin-1 during the progression of RCC. KEYWORDS caveolin-1, metastasis, microvessel density, prognosis, renal cell carcinoma OBJECTIVE To investigate the relationship of caveolin-1 expression and microvessel density (MVD), a reflection of angiogenesis, with metastasis and prognosis in patients with clear cell renal cell carcinoma (RCC). PATIENTS AND METHODS Formalin-fixed, paraffin-embedded tissue sections of clear cell RCC from 67 patients who had undergone radical nephrectomy were stained immunohistochemically with specific antibodies against caveolin-1 and CD34. Caveolin-1 immunostaining was semi-quantitatively estimated based on the proportion (percentage of positive cells) and intensity. MVD was determined with CD34- stained slides. The expression pattern of caveolin-1 and MVD was compared with the clinicopathological variables. INTRODUCTION Caveolae are vesicular invaginations of the plasma membrane involved in molecular transport, cell adhesion, and signal transduction [1–3]. Caveolin, a 21–24 kDa protein, is a principal structural component of caveolae. Three mammalian caveolin genes (caveolin-1, -2, and -3) have been identified. Caveolin-1 and -2 are co-expressed and form a hetero-oligomeric complex in many cell types, with particularly high levels in adipocytes, endothelial cells, and fibroblasts, whereas caveolin-3 expression is muscle- specific [3–5]. The diversity of cellular functions in which caveolins are involved relates to their interactions with many molecules, including G proteins, Ha-Ras, Src family tyrosine kinases, endothelial nitric oxide synthase, and epidermal growth factor receptor [3]. Altered caveolin expression is thought to be involved in several important human diseases, including cancer, diabetes, Alzheimer’s disease and muscular dystrophy [6]. Caveolin-1 is associated with tumour progression and metastasis in prostate and oesophageal cancer [7,8]; it may also be crucial in the organization of caveolae of endothelial cells and in regulating endothelial cell differentiation and angiogenesis, important mechanisms in tumour progression and metastasis [9–12]. RCC accounts for 2–3% of adult cancers and ª 85% of malignant renal tumours; it is a highly vascular neoplasm with an unpredictable pattern of recurrence. Although incidentally detected low-stage cancers show a good prognosis, metastatic RCC still has a poor prognosis [13]. Therefore, it is important to identify the markers that are correlated with metastasis and prognosis in RCC. Thus in the present study we investigated the expressions of caveolin-1 and microvessel density (MVD), a measure of angiogenesis, and related them to the clinicopathological variables in patients with clear cell RCC. PATIENTS AND METHODS Formalin-fixed, paraffin-embedded, archival surgical specimens from 67 patients (53 men and 14 women, mean age 54.5 years, range 33–81) diagnosed with primary clear cell RCC were assessed. All patients had undergone radical nephrectomy at our institution between January 1995 and August 2001. For the lymphadenectomy, only the renal hilar lymph nodes were routinely removed. If there were enlarged lymph nodes at surgery a node