C1D and neoplasm: Of note, multiple genes that were predominantly monoallelically expressed in tumor cell lines encode important epigenetic factors (e.g., CBX4 and BRD8), signaling cascade components (MAP2K3), cell cycle regulators (CDC27), and factors involved in DNA damage repair and maintenance of chromosomal stability (e.g., C1D and MAD2L2, or REV7) [151, 152, 167–171].