5-fluorouracil Low-dose 5-fluorouracil (5-FU) was found to inhibit systemic and lung accumulation of MDSC in tumor-bearing mice.126 5-FU mediated MDSC depletion was relatively strong when compared to gemcitabine and selectively triggered MDSC apoptosis in vitro and in vivo.127 5-FU, alone or in combination with bevacizumab, rapidly depletes circulating MDSCs and activates caspase 1.128 5-FU triggered IL-1 expression is detected in serum 24 h after treatment. The gene discussed is IL1B; the disease is neoplasm.