The invention is directed generally to a DNA sequence coding for human cyclin A and in particular to antibodies, or antisera including such antibodies, which bind to human cyclin A as encoded by the sequence of SEQ ID NO: 1 and which are useful in detecting cellular proliferation. The antibodies of the invention can be polyclonal or monoclonal, and are preferably generated by injection of purified human cyclin A into an animal host. The invention is particularly advantageous because it has been discovered that the gene encoding for human cyclin A is a site for integration of the hepatitis B virus associated with hepatocellular carcinoma, and by detecting human cyclin A through the use of the antibodies of the invention, one can detect and diagnose cell proliferation. Through the use of the present invention, cell proliferation and tumorigenesis can thus be detected at early stages, and such conditions can then be treated or inhibited by the use of anti-sense human cyclin A DNA.