Sitnikova L et al. (2008) IMP3 predicts aggressive superficial urothelial carcinoma of the bladder. Clin Cancer Res 14: 1701–1706

Jiang Z et al. (2008) Oncofetal protein IMP3: a novel molecular marker that predicts metastasis of papillary and chromophobe renal cell carcinomas. Cancer [doi:10.1002/cncr.23484]

Very few biomarkers are clinically useful for predicting tumor progression in urological cancers. U3 small nucleolar ribonucleoprotein IMP3, is involved in RNA trafficking and stabilization; this fetal oncoprotein influences cell growth and migration during embryogenesis. Two new studies have investigated the potential of this protein as a prognostic marker in renal and bladder cancers.

Sitnikova et al. reported a strong correlation between IMP3 expression and aggressive behavior of bladder carcinomas. IMP3 was expressed in 93% (26/28) of metastatic urothelial carcinomas, compared with 20% (42/214) of superficial urothelial carcinomas. During follow-up, 60% of the patients with IMP3-positive T1 superficial urothelial carcinomas developed metastases, compared with 0% of patients with IMP3-negative tumors. The authors concluded that IMP3-positive tumors were more likely than IMP3-negative tumors to become invasive or metastasize.

Jiang and colleagues found IMP3 to be an independent prognostic biomarker in a subgroup of patients with localized papillary and chromophobe renal cell carcinomas. They showed that patients with IMP3-positive carcinomas had a 10-fold greater risk of progression to distant metastasis than patients with IMP3-negative carcinomas (risk ratio 13.45, 95% CI 6.00–30.14; P <0.001).

Both studies indicate that IMP3 can potentially identify patients with a high risk of developing metastases; this information might help identify patients who could benefit from early aggressive treatment.