Tumor suppressor microRNAs are underrepresented in primary effusion lymphoma and Kaposi sarcoma

Abstract

IntroductionMicroRNAs (miRNAs) are a new class of genes that function as inhibitory RNA molecules that confer specificity to the RNAinduced silencing complex, which degrades the target mRNAs or inhibits protein translation. Because the biochemical function of miRNAs is to inhibit protein expression, it is not surprising that miRNAs can exhibit tumor suppressor phenotypes.Conversely, miRNAs have also been associated with growthpromoting phenotypes if their targets include tumor suppressor proteins or proteins that are required for cell differentiation. Many miRNAs are strictly cell lineage-associated, whereas others are found in multiple tissues, albeit at different levels. 1 Hence, miRNAs, like mRNAs, can be subjected to microarray profiling. Tumor signatures based on miRNA profiles have clinical predictive power, analogous to signatures based on mRNA profiles. 2 We have used real-time quantitative polymerase chain reaction-based arrays to profile miRNAs in 2 AIDS-defining cancers: primary effusion lymphoma (PEL) and Kaposi sarcoma (KS).PEL is a monoclonal CD138 ϩ , postgerminal center nonHodgkin B-cell lymphoma. 3 PELs express CD71 ϩ , CD38 ϩ activation markers and are invariably infected with KS-associated herpesvirus (KSHV). They can be dually infected with EpsteinBarr virus (EBV). EBV-positive and EBV-negative PEL can be differentiated based on their mRNA transcription pattern 4 but do not differ appreciably in culture or in animal models. 5,6 KS is also associated with KSHV infection. 7 KS is a malignancy of endothelial cells (ECs) and thought to be at the border between infectioninduced hyperplasia and clonal neoplasia.We find many known tumor suppressor miRNAs downregulated in PEL and KS. These include miR-155, miR-220/221, as well as miR-let7 family members. These miRNAs were more down-regulated in the monoclonal, fully transformed PEL than in KS biopsies or KSHV-infected, nontumorigenic ECs. This reinforces the importance of tumor suppressor miRNAs in oncogenic transformation and underscores their clinical utility for tumor classification. MethodsPELs are listed in Table S1 (available on the Blood website; see the Supplemental Materials link at the top of the online article). KS biopsies were obtained with informed consent obtained in accordance with the Declaration of Helsinki and used deidentified. Whole tonsil samples were used and obtained from the Cooperative Human Tissue Network. RNA was isolated as per our prior procedures, 8 and miRNA levels quantified using a commercial assay according to the manufacturer's recommendations (Applied Biosystems, Foster City, CA). Data were normalized to U6 RNA and clustered using Arrayminer (Optimal Design, Nivelles, Belgium). Analysis of variance, t test, and analysis of residuals after robust regression 9 were conducted in R (www.r-project.org). Results and discussionTo identify miRNAs that are down-regulated in KSHV-associated cancers, we profiled PELs, normal tonsil tissue, KSHV-infected and uninfected ECs, and, for the first time, primary KS biopsies. We had...

The manipulation of miRNA-gene regulatory networks by KSHV induces endothelial cell motility

“…This is the case in PEL and KS, because both miR-221 and miR-222 are down-regulated. 16 Although this is also true in infected BECs, we observed that there was asynchronous expression between miR-221 and miR-222 in KSHV-LECs. Furthermore, knocking down of LANA in KSHVECs restored only the expression level of miR-221 ( Figure 3D).…”

“…15 Furthermore, the miR-221 and miR-222 tumor-suppressor miRNAs were found to be significantly down-regulated in PEL and KS. 16 We found by array analysis that miR-221 and miR-222 target the ETS2 and ETS1 transcription factors, respectively. In vivo, the overlapping and redundant roles of ETS1 and ETS2 in the regulation of EC function and survival during embryonic angiogenesis has been discovered recently.…”

“…15,16 In KS and PEL, tumor-suppressor miRNAs such as miR-221, miR-222, and the let-7 family are underrepresented. 16 By comparing primary patient biopsies with well-established culture and mouse tumor models, it was found that the pre-miRNA signatures delineate the various stages of HUVEC transformation. 15 Loss of miR-221 and gain of miR-15 expression induce the transition of cells from The online version of this article contains a data supplement.…”

“…Among these 7 miRNAs, miR-221 and miR-222 have also been found to be down-regulated in PEL and KS tissues. 16 The differential expression of miR-221/miR-222, as well as miR-31, was examined by qRT-PCR, and their expression levels were also evaluated in KSHV-infected primary BECs. The expression of miR-221 was repressed in both infected LECs and BECs, whereas the level of miR-222 was only affected in infected BECs ( Figure 1E).…”

Genomic and Epigenomic Cross-talks in the Regulatory Landscape of miRNAs in Breast Cancer

“…It was shown that this miRNA was directly transactivated by p53, and is an important component of the p53 transcriptional regulatory network. Let-7 is also widely viewed as a tumor suppressor as the expression of let-7 is downregulated in many cancer types (57)(58). Figure 3 shows different targets of oncomiR miR-21 and oncosupressor miRNA let-7 in breast cancer and their putative functions.…”