Although breast cancer the most common cancer for women remains a significant health problem, it has not been systematically studied until now. In an attempt to identify novel genes implicated in breast cancer development. we performed a suppression subtraction hybridization (SSH) with human breast cancer tissues, as well as with cloned genes, that are expressed more than in normal tissue.

After the identification of a novel gene, RT-PCR was performed to determine its mRNA expression in human breast cancers. In order to learn more about the expression profile of this gene, PCR was performed using various commercially available normal or carcinoma cell lines. The novel gene was found to be strongly expressed in breast cancer tissues and other carcinoma cell lines. To determine whether this novel gene was associated with cell cycle regulation, normal WI-38 fibroblast cells were stimulated with media containing 0.1% FBS for 48hours.

From the experimental results of the SSH, a novel clone, "Clone 135", which was strongly expressed in tumor compared to matched normal tissue, has been found. The novel clone was identified as being expressed in several tumor tissues and carcinoma cell lines. The time-course expression of this novel gene in the WI-38 (8PDL) normal lung cell line indicated a significant increase for G1-phase arrest.

We have used a suppression subtractive hybridization (SSH) to generate a profile of genes overexpressed in human breast cancer. We have screened novel genes, of which "Clone 135" scored as a candidate oncogene that was overex-pressed in tumor compared to matched normal tissue.