AIDS-associated malignancies are in dire need of new therapies. Since their frequency in the general population is comparably low and since patients who develop AIDS-associated malignancies are often too sick to participate in experimental treatments, clinical trials in AIDS-associated malignancies are faced with low enrollment. How then, can we nevertheless obtain clinical data that support the efficacy of novel therapeutics? This is a general obstacle faced by all who study disease that affect marginal or especially vulnerable populations. One solution is the use of biomarkers to support studies of drug action. Here we used a targeted approach to identify biomarkers that are relevant for AIDS associated malignancies and that can be developed into biomarkers for the evaluation of drugs that affect the NFkB pathway. We focused on the NFkB pathway, because it is central to gamma-herpesvirus-associated cancers, which in turn are overrepresented among AIDS patients 21
We identified CD69, CSF-1, and complement factor B (C1QBP) as PEL specific biomarkers that are known downstream targets of NFkB. We identified IL1-beta, cyclin D3 and CD48 as NFkB-regulated KS specific biomarkers. These NFkB targets were not expressed in BL or ATL.
We obtained evidence in support of two molecular subtypes of BL, which can be differentiated on the basis of their EBV status and we determined thatCox-2, TNFalpha, and CCR5 were robustly expressed only in EBV positive BL. This corroborates a recent study by Piccaluga et al 22
, who were able to distinguish BL from other NHL, but more importantly who also distinguished three types of BL--endemic, spontaneous, and HIV-associated on the basis of mRNA profiling. Further this study found that genes in the TNF/NFkB pathway were overrepresented among the mRNAs that differentiated among BL subsets. This underscores the utility of pathway-targeted profiling if biological insights or larger scale data suggest particular biological pathways.
We obtained evidence in support of molecular subtypes of ATL that were not linked to histological stage. However, we did not have the statistical power to identify any one specific biomarker in our targeted arrays, which could differentiate between these two subtypes.
Lymphomas have been the subject of innumerous profiling studies. Studies on AIDS-associated lymphomas or KS are rarer 13, 14, 16, 17, 23
. Some of the new biomarkers that we discovered here, were previously investigated:C1QBP had been detected in PEL, but the other two markers (CD69, CSF-1) were not previously associated with PEL. CD69 was originally identified as a T cell activation marker, but is also highly transcribed in follicular lymphoma 24
. This also holds true for CSF-1 and C1QBP. In regard to KS profiling data are even more limited. CyclinD3
is a bona fide endothelial cell marker, expression of which correlates with CD31levels. CD48 is expressed in endothelial cells as well as leukocytes and can be up regulated by LPS (via NFkB) and VEGF-1.
Cox-2, TNFalpha, and CCR5 were the most robustly differentially transcribed NFkB targets in our two BL subsets. Higher mRNAlevels correlated with the presence of EBV. In PEL, high levels of IL12, jun-B, msx-1 and thrombospondin 2 were best correlated with the presence of EBV. This suggests an important generalization: whereas EBV modulates NFkB signaling, it is the tumor tissue of origin that restricts which NFkB target gene repertoire that is open to regulation by the virus.
Some NFkB target genes emerged that were universally present and that could be used to follow drug effects in a large variety of different cancers. This is not entirely unexpected and underscores the importance of multi-analyte assays in cancer research. Unfortunately this would also suggest that single biomarker responses can not be compared between tumor types or even between lymphoma subtypes.
These biomarkers are clinically relevant because many agents that target NFkB in cancer are in advanced clinical testing. These biomarkers are robust, because they can be measured individually by real-time qPCR. We hope that they facilitate the testing of novel NFkB inhibitors for AIDS-associated malignancies.