Abstract: Cyclin E/cyclin-dependent kinase2 (CDK2) complex plays a key role in the G1/S transition of cell cycle. Full-length cyclin E (FL-E) is mainly expressed in normal tissues and cells, whereas low molecular weight cyclin E (LMW-E) can only be found in tumors. LMW-E is more stable with higher cyclin E/CDK2 kinase activity compared to FL-E, results in genomic instability and deregulation of cell cycle, and leads to endocrine resistance in breast cancer treatment. As an important biological marker of tumor prognosis, LMW-E may also be a potential target for its biological treatment.

Key words: Low Molecular Weight Cyclin E and its Relation with Malignant Tumors, Cyclin E, Breast cancer, Low molecular weight, Protease, Cell cycle