Endometriosis is a complex gynecological disease which occurs in 10% of reproductive age women. The disease is characterized by the presence and growth of endometrial tissue outside the uterus, causing pelvic pain, and Axitinib infertility. The pathogenesis of endometriosis is not clearly defined. However, the disease is thought to be principally caused by the shedding of viable endometrial cells into the peritoneal cavity by retrograde menstruation, followed by their implantation and growth on the surface of pelvic organs. The formation of a lesion depends on the survival, attachment, growth, neoangiogenesis, and invasion of the endometrial cells at the ectopic sites. This may be due to abnormalities of the eutopic endometrium itself, predisposing the cells to survive and implant ectopically. Several studies have shown aberrant expression of genes/ proteins in endometriosis that are involved in regulating cellular processes like adhesion, proliferation, angiogenesis, immune dysfunction, and others. Recently, using proteomics approach, we have investigated the differential expression of proteins in eutopic endometrium from women with and without endometriosis. In this study it was observed that DJ-1 protein is upregulated in eutopic endometrium of women having endometriosis compared with controls. These findings suggest that DJ-1 may be involved in the pathogenesis of endometriosis. The human DJ-1 gene comprises of seven exons and maps to 1p36.2-36.3, where many chromosome aberrations in cancers have been reported. DJ-1 is ubiquitously present in cells and has been suggested to be a novel mitogen-dependent oncogene involved in a Ras-related signal transduction pathway. More recently, high DJ-1 levels have been reported in various tumors, suggesting that abnormally expressed DJ-1 may play a role in cancer initiation and/or progression under certain circumstances and may be a potential anticancer target. DJ-1 protein affects cell survival, proliferation, and growth of cells in part, by modulating cellular signaling cascades such as PTENPI3K/ Akt and altering p53 activity. DJ-1 has shown to convey protection against stresses and proteasome inhibition. It has been suggested that DJ-1 plays a role in antioxidative stress by eliminating reactive oxygen species and in transcriptional regulation of its target genes. The pathological significance of DJ-1 in endometriosis has not been elucidated. Therefore, we investigated the effect of DJ-1 on normal endometrial as well in endometriotic cell survival, proliferation, motility, and invasion. An analysis of endogenous DJ-1 expression in normal human endometrial epithelial and stromal cell lines and endometriotic epithelial and stromal cell lines was performed. It was observed that the expression of DJ-1 protein was relatively higher in endometriotic cell lines compared to normal endometrial cell lines. Ishikawa, which is an adenocarcinoma cell line, was used to show that the DJ-1 expression levels in endometriotic cells were similar to that in endometrial cancer cells. Cellular adhesion of normal endometrial and endometriotic cells on various extracellular matrix components was performed to understand whether endometriotic cells have the ability to attach at ectopic location. For this, normal endometrial and endometriotic cells were plated on dishes precoated with various ECM components. As shown in Figure 2A, endometriotic epithelial cells attached significantly more on fibronectin and laminin but not on collagen type IV when compared to normal endometrial epithelial cells. Endometriotic stromal cells show more attachment on laminin but less on collagen type IV when compared with normal endometrial stromal cells. However, no significant difference in attachment was observed between normal endometrial and endometriotic stromal cells on fibronectin. To determine whether DJ-1 augments cellular adhesion, normal endometrial cells were infected with DJ-1 or control adenovirus for 24 h and cell adhesion assay was performed. It was observed that HES cells overexpressing DJ-1 show increased attachment on collagen type IV when compared with controls. The attachment was found to be decreased on fibronectin and laminin. This finding is interesting, as collagen type IV is one of the major matrix components found in the basement membrane of normal tissue and organ.We have checked the expressions levels of DJ-1 on various extracellular matrix components after infection with DJ-1 adenovirus using immunoblotting, the expression levels of DJ-1 was found to be similar. Similar experiments were carried out using Sht 290 cells. With this cell line, no significant difference in attachment to collagen type IV, fibronectin or laminin was observed between DJ-1 overexpressing cells and controls. The role of DJ-1 in endometrial and endometriotic cell proliferation was ascertained by using siRNA and overexpression approach. The success of siRNA transfection was 85-90% and DJ- 1 gene silencing was upto about 80% in endometriotic cells. The cell growth kinetics indicated that downregulation of DJ-1 by silencing DJ-1 gene decreases endometriotic epithelial and stromal cell proliferation by,2.5 and,1.5 fold, respectively when compared with controls. However, the inhibitory effect was more in endometriotic epithelial cells than in stromal cells. The experiment was also repeated using a second siRNA targeting DJ-1, and similar results were obtained as shown in Figure S2C and S2D. Further we determined, whether overexpression of DJ-1 affects cell proliferation in normal endometrial cells. Overexpression of DJ-1 in normal endometrial epithelial cells enhances cell proliferation by 1.4 fold within 48 h and it was 1.83 fold more by 72 h when compared with controls.