Diagnostic role of kidney injury molecule-1 in renal cell carcinoma

Despite rapid advances in diagnostic and therapeutic medicine, renal cell carcinoma (RCC) continues to cause significant morbidity and mortality in patients. While there has been a shift towards earlier detection, approximately 16% of patients present with metastatic disease at the time of diagnosis. Kidney injury molecule-1 (KIM-1) is a glycoprotein that has been shown to be a robust and reliable biomarker of acute proximal tubular injury. As KIM-1 is mainly expressed in RCC derived from the proximal tubules, it is a reliable marker to differentiate between proximal tubular primary RCC and distal nephron primary RCC. Several studies have investigated urinary KIM-1 (uKIM-1) in RCC and demonstrated that it is a sensitive and specific marker for detecting localized RCC, as patients had markedly reduced uKIM-1 levels following nephrectomy, with uKIM-1 levels correlating with tumor size and grade. In addition, levels of KIM-1 present in plasma have also shown utility as a biomarker of RCC with levels being elevated in RCC cases at least 5 years before diagnosis. This review focuses on a progressive understanding of KIM-1 in the diagnosis of RCC using biopsies, urine, and plasma samples, and it will also provide some insight into potential roles of KIM-1 in the growth and spread of RCC.