MMP1 and renal cell carcinoma: Similarly, homozygotes for the “high-risk” MMP1 allele (rs1799750, c.-1607 2G) had an earlier onset of RCC than patients homozygous for the “low risk” MMP1 allele (rs1799750, c.-1607 1G), with heterozygotes having an intermediate risk (see Figure 2A).