hcdc4 (archipelago)Endometrial Cancer Andrew Marshall April, 1, 2004
hcdc4 • Highly conserved throughout evolution • Ago (Drosophila), SEL-10 (nematode and mouse), and cdc4 (yeast) • Locus – 4q.32 (mutated in 30% human tumors) • F-Box and WD40 Domains (FBXW7) • Repeated sequences of W (tryptophan) and D (aspartic acid) (Strohmaier (2001))
hcdc4 and Cyclin E • Through various screens, we know the WD Domain serves as a dock for Cyclin E • Together with other molecules forms a functional SCF-type protein ubiquitination ligase
Cyclin E and Cell Cycle Control • The up and down cycles of Cyclin E are responsible for the G1-S Transition • But how are these levels controlled?
The Ubiquitination Cascade • Following the E1 to E2 and finally to E3 Ubiquitin Pathway • Thus, marking the target (cyclin E) with a polyubiquitin chain • Degradation by the Proteosome • Tumor Suppressor (negative regulator of cell proliferation)
What’s the Big Deal? • We Know • hcdc4 controls Cyclin E levels through the ubiquitin cascade • Cyclin E levels control the cell cycle • The cell cycle is..... Important
The hcdc4 -/- (SEL-10) mouse is inviable • Halted development due to meiotic mistakes very early in development • Drosophila Model (Ago) • Over proliferation due to failure to exit cell cycle • Photoreceptor problems (Moberg 2001)
Chromosomal Instability • Aneuploidy • Gene Amplification • Chromosome Rearrangements, Inversions, Translocations, and Deletions • Spindle Apparatus failure • And in this Case, also Micronuclei (Rajagopalan (2004))
Checkpoints • The Cell Cycle Must • Introduce no mistakes • Maintain diploidy • Am I Big Enough? • Am I OK?
Prove It! • A definitive association between hcdc4 mutants and overexpression of Cyclin E • Without overexpression of Cyclin E mRNA • LOH • Restoration of correct cyclin E expression via retroviral transduction (Strohmaier (2001)) (Reed (2004))
Accumulation, Accumulation, Accumulation • Cancer takes more than one mutation • Increased chances with • Increased Cells • Increased proliferation due to constitutively active Cyclin E pushing cells from G1 to S (proliferative advantage) • DNA Problems • Chromosomal Instability due to that same push towards the S Phase • Accelerated lost of heterozygosity
What Do We Get?Cancer! • More specifically, endometrial cancer • A cancer of the lining of the uterus
Endometrial Cancer • How do we Really Know hcdc4/Cyclin E is the cause? (Spruck (2002))
Not So Fast • Not all endometrial cancers contain the hcdc4 mutation • 20% of cases with elevated Cyclin E levels • Although, Those that do are associated with increased metastasis and severity • Possible Reasons • Cyclin E regulated by different pathways • hcdc4 mutations of WD40 region and amino terminus • Different variants of hcdc4 (Cassia (2003))
Still a Mystery • Although a great deal of research has been done on hcdc4 of late, many of its functions remain to be understood • Notch Pathway • Alzheimer's • Different Targets and Different Roles
Works Cited • Cassia, Raul, Moreno-Bueno, Gema, Rodriguez-Perales, Sandra, Hardisson, David, Cigudosa, Juan C., and Palacios M.D., Jose. Cyclin E gene (CCNE) amplification and hCDC4 mutations in endometrial carcinoma. The Journal of Pathology 201 589-595 (2003). • Moberg, Kenneth H., Bell, Daphne W., Wahrer, Doke C.R., Haber, Daniel A., and Hariharan, Iswar K. Archipelago regulates Cyclin E levels in Drosophila and is mutated in human cancer cell lines. Nature 413, 311-316 (2001). • Rajagopalan, Harith, Jallepalli, Prasad V., Rago, Carlo, Velculescu, Victor E., Kinzler, Kenneth W., Vogelstein, Bert, and Lengauer, Christoph. Inacivation of hCDC4 can cause chromosomal instability. Nature 428, 77-81 (2004). • Reed, Susanna Ekholm, Spruck, Charles H., Sangfelt, Olle, van Drogen, Frank, Mueller-Holzner, Elisabeth, Widschwendter, Marrtin, Zetterberg, Anders, and Reed, Steven I. Mutation of hCDC4 Leads to Cell Cycle Deregulation of Cyclin E in Cancer. Cancer Research 64, 795- 800 (2004). • Spruck, Charles H., Strohmaier, Heimo, Sangfelt, Olle, Muller, Hannes M., Hubalek, Michael, Muller-Holzner, Elisabeth, Marth, Christian, Widscwendter, Martin, and Reed, Steven I. hCDC4 Gene Mutations in Endometrial Cancer. Cancer Research 62, 4535-4539 (2002). • Strohmaier, Heimo, Spruck, Charles H., Kaiser, Peter, Won, Kwang-Al, Sangfelt, Olle, and Reed, Steven I. Human F-box protein hCdc4 targets Cyclin E for proteolysis and is mutated in a breast cancer cell line. Nature 413, 316-322 (2001).