Quantitative analysis of NM23 protein immunoreactivity in renal cell carcinoma using an image analyzer

nm23 is a candidate tumor suppressor gene. Whether or not tumor metastasis suppressive activity is present in renal cell carcinoma (RCC) was studied.

Immunohistochemical analysis of nm23 protein using an anti-human nm23 H1/H2 polyclonal antibody was performed in 67 RCCs and in the corresponding 67 normal proximal renal tubules (NTs). The quantity and intensity of nm23 protein immunoreactivity were evaluated using a computer-interfaced image analyzer, and the obtained results were compared with pathological findings and clinical outcome.

The quantity and intensity of nm23 protein immunoreactivity were significantly higher in RCCs than those observed in NTs (p <0.0001, respectively). Both quantity and intensity of nm23 protein immunoreactivity held a tendency to increase along with histological grade (p = 0.094 and p = 0.089, respectively) and T category (p = 0.063 and p = 0.063, respectively). Similarly, the immunoreactivity had a tendency to be higher in RCCs with lymph node involvement than those tumors without involvement (p = 0.060 and p = 0.067, respectively). However, no significant difference in nm23 protein immunoreactivity was found between tumors with and without distant metastasis. Using a univariate analysis, a high nm23 protein immunoreactivity (quantity > or = 51.0% or intensity > or = 72.5%) significantly correlated with a poor clinical outcome (p = 0.0051 and p = 0.0013, respectively). Furthermore, a multivariate analysis adjusted to age, T, N and M categories, showed that a high intensity of nm23 protein immunoreactivity was significantly associated with a poor clinical outcome in patients with RCCs (p = 0.0192).

Immunohistochemical analysis of nm23 protein intensity is an additional tool for analyzing the difference of biological features in RCCs. The potential role of the tumor metastasis suppressive activity of nm23 remains unclear in RCCs.