Small proline rich repeat protein 3 (SPRR3), a member of the SPRR family of cornified envelope precursor proteins, is a marker for terminal squamous cell differentiation. Previously, this laboratory showed that SPRR3 is strongly upregulated in colorectal tumors, and is involved in the tumorigenesis. The current study was performed to investigate the expression status and effect of SPRR3 in breast cancers (BCs). SPRR3 expression was examined by immunohistochemistry in 241 tumor samples from BC patients. SPRR3 was overexpressed in more than half of all BC samples. SPRR3 overexpression was significantly associated with less advanced stage (0-1 vs. II-III) and the absence of lymph node metastasis (P = 0.004 and 0.013, respectively). HER2/neu overexpression was closely correlated with SPRR3 overexpression in a multivariate analysis (OR, 3.23, P = 0.017). To assess the influence of SPRR3 on cell proliferation and related signaling pathways, SPRR3-transfected clones from the SPRR3-negative T-47D human BC cell line were generated. Among the total of six SPRR3-overexpressing clones, five showed marked proliferation compared with SPRR3-nonexpressing control cells from day 3 of culture (P < 0.001). The SPRR3-overexpressing BC clones showed increased phosphorylation of AKT and MDM2, p21 overexpression, and p53 downregulation. Furthermore, phosphorylation of MEK and MAPK was markedly increased. This study demonstrates that SPRR3 promotes BC cell proliferation by enhancing p53 degradation via the AKT and MAPK pathways and is, therefore, a potential novel therapeutic target for less advanced stages of BC.

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Purpose Few efficient methylation markers of chemosensitivity have been discovered. The genome-wide analysis of methylation markers is needed to identify chemosensitive candidates to targeted therapy. Methods This study describes a two-step process to select chemosensitive candidates of methylation genes. A genome-wide screening of methylation genes was performed using a beadarray and an in vitro chemosensitivity assay of 119 colorectal cancers (CRCs). Results Ten candidate genes identified during the initial screening were verified by biological utility assessment using cell viability assays of transfected CRC cells. Five methylation genes related to sensitivity to bevacizumab regimens (RASSF1, MMP25, KCNQ1, ESR1, and GALR2) or cetuximab regimens (SCL18A2, GPX7, NID2, IGFBP3, and ALX4) were chosen during the first step. A viability assay revealed that GALR2-overexpressing HCT116 cells were significantly more chemosensitive to bevacizumab regimens than control cells (P = 0.022 and 0.019 for bevacizumab with FOLFIRI and FOLFOX, respectively), concurrently verified on a caspase-3 activity assay. GPX7- or ALX4-overexpressed RKO cells were significantly less viable to cetuximab regimens compared to control cells (GPX7: P = 0.027 each for cetuximab with FOLFIRI and FOLFOX; ALX4: P = 0.049 and 0.003 for cetuximab with FOLFIRI and FOLFOX, respectively), but caspase-3 activity was not prominent in GPX7-overexpressed RKO cells. Conclusions Two novel genes, GALR2 and ALX4, have been identified as chemosensitive methylation candidates to bevacizumab and cetuximab regimens, respectively. As our study did not include a clinical association study, the two candidates should be validated in large clinical cohorts, hopefully predicting responsive patients to targeted regimens. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4590. doi:1538-7445.AM2012-4590