Impact of G-CSF Therapy on Leukopenia and Acute Rejection Following Kidney Transplantation

BACKGROUND

Leukopenia is a common problem after kidney transplantation. The therapeutic approach typically includes a reduction of the immunosuppressive therapy, which is associated with an increased risk of rejection and allograft loss. Granulocyte colony-stimulating factor (G-CSF) is used as a therapeutic option to raise the leukocyte blood count; however, the effect on acute rejections is controversial.

OBJECTIVE

The goal of this study is to examine the incidence of acute rejections following G-CSF therapy.

METHODS

We retrospectively evaluated patients with leukopenia following kidney transplantation and GCSF therapy between January 2007 and December 2017 at our center compared to controls with matched minimal leucocyte blood count in a matched pair analysis.

RESULTS

We identified 12 patients, who received G-CSF therapy with a cumulative dose of 10.74 µg/kg body weight over a time frame of 4.3 days. G-CSF therapy resulted in a significantly shorter time period with leucocytes <3,000/µL (9.5 vs. 16.6 days), but also trended towards an increased risk of rejection within the next 30 days with three patients in the G-CSF group and no patient in the control group (p=0.06) developing an acute biopsy-proven rejection. Infection and mortality rate in the subsequent year were not different between groups.

CONCLUSION

G-CSF therapy decreases the duration of leukopenia post-kidney transplantation, but may also increase the risk of an acute rejection.

Abstract P5-05-03: Upregulated purinergic signaling enhances cell proliferation in human and murine breast carcinomas

The composition of the extracellular tumor microenvironment differs from that of most other tissues and is thought to provide cancer cells with a growth and survival advantage compared to normal cells. In solid tumors, the extracellular concentration of ATP can be elevated to ~100 µm and extracellular pH can be as low as 6.5. In the current project, we investigate the consequences of purinergic signaling in human and murine breast carcinomas: we study intracellular Ca2+ signals and associated changes in cell proliferation during stimulation with extracellular nucleotides.

We employ biopsies of human and murine primary breast carcinomas and compare them with matched normal breast tissue. Human biopsies are obtained with written informed consent from patients undergoing breast conserving surgery at Aarhus University Hospital or Regional Hospital Randers in Denmark. Murine biopsies are from mice overexpressing unactivated ErbB2 specifically in the breast tissue. We isolate epithelial organoids (~150 µm diameter) from tissue biopsies by partial digestion with collagenase III. Organoids loaded with the Ca2+-sensitive fluorophore Fura-2 are studied by fluorescence microscopy. In separate experiments, cell proliferation is quantified by detecting newly synthesized DNA using immunofluorescence imaging of organoids incubated with the thymidine analogue bromodeoxyuridine (BrdU).

We find that intracellular Ca2+ responses during stimulation with extracellular ATP are elevated 2- to 10-fold in breast carcinomas from mice and humans, respectively, compared to matched normal breast tissue. We observe similar differences between breast cancer tissue and normal breast tissue in response to stimulation with the P2Y2/P2Y4-agonist UTP, whereas virtually no rise in the intracellular concentration of Ca2+ is observed in response to the P2X7-agonist 3'-O-(4-benzoyl)benzoyl-ATP. Application of cyclopiazonic acid – an inhibitor of the sarcoplasmic/endoplasmic reticulum Ca2+-ATPase – also cause exaggerated intracellular Ca2+ responses in breast cancer compared to normal breast tissue. Consistent with the elevated Ca2+ responses, stimulation with 100 µm ATP or 100 µm UTP increases the rate of cell proliferation (i.e., fraction of BrdU-positive cells) by ~2-fold in the breast cancer tissue.

In conclusion, we find that purinergic signaling is upregulated in human and murine breast carcinomas compared to normal breast tissue. Activation of purinergic receptors – most likely P2Y2 and/or P2Y4 – enhances cell proliferation in breast cancer tissue. We propose that the high ATP levels in the tumor microenvironment promote breast cancer development or progression and that the associated signaling pathways represent promising targets for therapy.

Citation Format: Mele M, McWhan K, Henningsen M, Vahl P, Jensen V, Johansen T, Pedersen H, Christiansen P, Bødtkjer E. Upregulated purinergic signaling enhances cell proliferation in human and murine breast carcinomas [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P5-05-03.

Genetic analysis of the maternally induced affinity enhancement in the non-Ox1 idiotypic antibody repertoire of the primary immune response to 2-phenyloxazolone

The early phases of ontogeny are decisive for the development of the B-cell repertoire. Here, we demonstrate that maternal tertiary immunization of BALB/c mice with 2-phenyloxazolone (phOx) caused a drastic alteration of the primary antigen-specific repertoire of the offspring. Maternal tertiary immunization or quaternary antibodies, which exhibited an extremely weak cross-reactivity with the major Ox1 idiotype (IdOx1), induced a change in the proportion of IdOx1/non-IdOx1 antiphOx antibodies in the F1 and F2 primary repertoire. The observed variability in the level of IdOx1 expression (10-90%) exceeded even the seemingly genetically based differences between various mouse strains. In comparison with the non-IdOx1 of control mice, half of the non-IdOx1 antibodies showed a 5-100-fold enhanced affinity. Sixty per cent of these antibodies exhibited an affinity identical to that of IdOx1 antibodies, which are normally of the highest affinity, while the remaining 40% exceeded even that of IdOx1 by a factor of 10. The non-IdOx1 were encoded by VH/VL genes and/or combinations thereof which are either new, hitherto unobserved in the antiphOx response, or typical of memory responses in normal mice. The significance of these data is discussed with respect to the possibility that maternal antibodies, which are acquired through multiple immune maturation processes, may have an epigenetic (non-Mendelian) inheritable potential for the offspring.

Cloning, sequencing and expression of the sialidase gene from Actinomyces viscosus DSM 43798

Chromosomal DNA from Actinomyces viscosus was digested with restriction endonucleases and the fragments ligated with pUC-vectors were used to transform Escherichia coli cells. Clones bearing the required sialidase gene were detected by spraying the colonies with the fluorogenic sialidase substrate MU-Neu5Ac. The identity of the cloned sialidase was confirmed after the 5700-fold enrichment and comparison with the purified enzyme of A. viscosus. Both sialidases were identical with regard to molecular mass, substrate specificity tested with sialyllactoses, and the inhibition of their activity by heterologous antisialidase antibodies. The sequenced insert (EMBL accession number X62276) revealed a mol% G + C of 68.2, typical for A. viscosus. An open reading frame of 2739 bp follows a sequence with dyad symmetry and an AG-rich region, and codes for 913 amino acids representing a molecular mass of 113 kDa. The conserved amino acid sequence [Ser-X-Asp-X-Gly-X-Thr-Trp] typical for bacterial sialidases was found at five positions in the predicted amino acid sequence. The gene of this enzyme is expressed by E. coli, despite the low relatedness of both species.