Abstract: The invention relates to a method of detecting an actively cycling cell in a sample, said method comprising determining the state of GINS gene expression within said cell, wherein detection of GINS gene expression in said cell indicates that said cell is actively cycling. Furthermore, the invention relates to methods for detecting an actively cycling cell in a subject, said method comprising assaying a sample from said subject for evidence of GINS gene expression, in particular when the sample is a body fluid such as urine. Preferable the GINS gene is PSFI or SLD5, in particular SLD5, in particular SLD5. The invention also relates to use of a PIKK family kinase in the in the phosphorylation of GINS, in particular when the kinase is selected from the group consisting of S. Cerevisiae Mecl and Tell, human ATR, ATM and DNA-PK.