Differential Genomic and Proteomic Signatures In Cord Blood (CB) Vs Peripheral Blood (PB) CD56^+Dim NK Cells: Over Expression of CD34 In CB Vs PB CD56^+Dim NK Cells

Umbilical cord blood (UCB) is a viable alternative source of allogeneic hematopoietic stem cells for the treatment of both malignant and non-malignant disease (Cairo et al BBMT 2008). UCB transplantation (UCBT) is known to be associated with decrease severe acute graft-versus-host disease (GvHD) compared to unrelated bone marrow (BM) and peripheral blood (PB) transplantation; however, it is associated with delayed hematopoietic and immune reconstitution (Szabolcs/Cairo et al Seminars in Hematology 2010). NK cells play important roles in both innate and adaptive immunity and are characterized as a CD56⁺ cell population. NK cell recovery is prompt by 2 months after hematopoietic stem cell transplantation (HSCT), while T-cell (after at least 9 mo HSCT) and B-cell (after 3 to 4 mo HSCT) reconstitutions are gradual and delayed. CD56^+dim cells are primarily cytotoxic and make up 90% of PB NK populations (Shereck/Cairo PBC 2007). We previously demonstrated the ability to ex-vivo expand CB MNC into various phenotypes of CD56^+dim and CD56^+bright NK cells (totally 60%) and NKT cells (40%) with profound in vitro and in vivo cytotoxicity against hematological malignancies (Ayello/Cairo BBMT 2006 & Exp. Hematology 2009). Proteomic studies from our group demonstrated differential protein expression including ↑NKG2A, ↓IP3R type 3, ↓MAPKAPK5, and ↑NOTCH 2 in CB vs PB CD56^+dim (Shereck/Cairo, ASH 2007; Shereck/Day/Cairo, ASBMT 2009).

In these studies, we sought to determine the similarity or differences in genetic signatures in CB vs APB CD56^+dim NK cells.

CB MNCs were isolated on a ficoll gradient and NK CD56⁺16^+dim cells isolated using a 2-step magnetic activated cell separation (MACS) process via a standard kit (Miltenyi Biotec). Enrichment was at least 94%. Isolated RNA from CB and PB CD56^+dim cells were subjected to microarray studies (Affymetrix, U133A_2) as we have previously described (Jiang/Cairo et al J Immunol 2004). Data were analyzed by Agilent GeneSpring and Ingenuity pathway analyses. Welch test were used to perform statistical analysis and fold change of < 1.5 and values of p<0.05 were considered to be significant. Two-color ECL Plex fluorescence Western blotting (WB) was preformed to validate the proteomic data. Protein samples were separated using SDS-PAGE followed by transblotting. WB membranes were then incubated with target and control (GAPDH) primary antibodies. After rinse and wash, the membranes were further incubated with CY5 and CY3 conjugated secondary antibodies. The membranes were scanned with TYPHOON by green (532 laser and 580 filter) and red (633 laser and 670 filter) setting for CY3 and CY5, respectively, and then observed and quantified using ImageQuant.

CB vs PB CD56^+dim cells significantly altered expressed 796 genes, in which 486 genes were over expressed, at the genomic level including: pro-apoptotic genes: CASP10 (3.1F), TNFSF11 (4.7F), CDC2 (3.0F), BCL2L1 (4.3F), NOTCH2 (1.5F); and cell development: PBX1 (7.6F), IL1RN (5.1F), CD24 (5.3F), CD34 (3.5F), CD55 (2.1F), CCL13 (2.2F). Conversely, there was significant under expression of NF1 (5.1F), MAP2K3 (1.7F), PIK3CD (2.1F), BAX (2.9F), and JUN (2.2F). Our WB results indicate that NOTCH2 (2.4F) and PBX1 (2.2F) proteins are increased in CB vs PB CD56^+dim NK cells, consistent with our proteomic results.

These results suggest that CB vs PB CD56^+dim NK are more prone to undergo programmed cell death (apoptosis) secondary to over expression of numerous pro-apoptotic genes, and may be earlier in development (pro-NK) with over expression of the CD34 gene. Furthermore, decrease CB vs PB NK cytotoxicity maybe in part secondary to increase programmed cell death in particularly increase NOTCH2 at the genomic and proteomic levels. (The first two authors contribute equally.)

No relevant conflicts of interest to declare.