Kreinest, Pamela

Abstract Primary central nervous system (CNS) lymphoma (PCNSL) is a diffuse large B-cell lymphoma (DLBCL) confined to the CNS. A genome-wide gene expression comparison between PCNSL and non-CNS DLBCL was performed, the latter consisting of both nodal and extranodal DLBCL (nDLBCL and enDLBCL), to identify a “CNS signature.” Pathway analysis with the program SigPathway revealed that PCNSL is characterized notably by significant differential expression of multiple extracellular matrix (ECM) and adhesion-related pathways. The most significantly up-regulated gene is the ECM-related osteopontin (SPP1). Expression at the protein level of ECM-related SPP1 and CHI3L1 in PCNSL cells was demonstrated by immunohistochemistry. The alterations in gene expression can be interpreted within several biologic contexts with implications for PCNSL, including CNS tropism (ECM and adhesion-related pathways, SPP1, DDR1), B-cell migration (CXCL13, SPP1), activated B-cell subtype (MUM1), lymphoproliferation (SPP1, TCL1A, CHI3L1), aggressive clinical behavior (SPP1, CHI3L1, MUM1), and aggressive metastatic cancer phenotype (SPP1, CHI3L1). The gene expression signature discovered in our study may represent a true “CNS signature” because we contrasted PCNSL with wide-spectrum non-CNS DLBCL on a genomic scale and performed an in-depth bioinformatic analysis.

Abstract Purpose: Incidence and mortality rates for renal cell carcinoma (RCC) have been rising for decades. Unfortunately, the molecular events that support RCC carcinogenesis remain poorly understood. In an effort to gain a better understanding of signaling events in clear cell RCC (cRCC), we investigated the antitumor activity of secreted frizzled-related protein 1 (sFRP1), a negative regulator of Wnt signaling. Experimental Design: Genomic profiling of cRCC tumors and patient-matched normal tissues was done and confirmed using quantitative PCR and immunohistochemistry. Methylation-specific PCR was done on patient samples to evaluate the mechanism responsible for sFRP1 loss. sFRP1 expression was restored in cRCC cells and the effects on tumor phenotype were characterized. Results: Genomic profiling, quantitative PCR, and immunohistochemistry indicated that loss of sFRP1 occurred in cRCC and papillary RCC patient tissues. Twelve Wnt-regulated genes were up-regulated in cRCC tissues, including c-myc and cyclin D1, potentiators of cell proliferation and survival. Methylation of the sFRP1 gene was one mechanism identified for attenuation of sFRP1 mRNA. Stable reexpression of sFRP1 in cRCC cells resulted in decreased expression of Wnt target genes, decreased growth in cell culture, inhibition of anchorage-independent growth, and decreased tumor growth in athymic nude mice. Conclusions: To our knowledge, this is the first report to show that stable restoration of sFRP1 expression in cRCC cells attenuates the cRCC tumor phenotype. Our data support a role for sFRP1 as a tumor suppressor in cRCC and that perhaps loss of sFRP1 is an early, aberrant molecular event in renal cell carcinogenesis.