RB1 and malignant colon neoplasm: Several additional regulators of chromatin structure and transcription were directly enhanced by RB1 loss-of-function and/or E2F activation, including RBBP4, a ubiquitous component of histone deacetylase complexes that was upregulated in an RB1-mutation-driven embryonic brain tumor model in zebrafish [36] and is known to enhance mesenchymal marker expression and invasion in human cervical and colon cancer cell lines [37,38].