High levels of IL-4 and IL-10 mRNA and low levels of IL-2, IL-9 and IFN-gamma mRNA in MuLV-induced lymphomas

Use of quantitative real-time PCR to determine immune cell density and cytokine gene profile in the tumor microenvironment

BACKGROUND

The molecular mechanisms underlying tumor responsiveness to immunotherapeutic manipulations remain elusive. Investigators are therefore searching for new technologies to study immune-related events occurring in the tumor microenvironment.

AIM

To validate the use of quantitative real-time PCR (qrt-PCR) for assessing immune cell density and cytokine (CK) gene profile in tumor biopsies obtained from patients treated with TNFalpha-based isolated limb perfusion.

MATERIALS AND METHODS

We first assessed in vitro the ability of cell marker coding genes (CD4, CD8, CD14, CD56) to serve as housekeeping genes for helper and cytotoxic T-lymphocytes, macrophages and NK cells, respectively. Then, the correspondence between mRNA and protein levels of five CK (IL-2, IFNgamma, IL-4, IL-10 and TGFbeta1) expressed by stimulated PBMC was evaluated by means of qrt-PCR and ELISA, respectively. Finally, six patients affected with locally advanced soft tissue sarcomas underwent tumor biopsy before and after TNFalpha-based isolated limb perfusion. After RNA extraction and amplification, transcriptional levels of the above cell markers and CK were evaluated by qrt-PCR.

RESULTS

In vitro, leukocyte cell subsets constantly expressed the corresponding marker gene both under resting conditions and after cell stimulation. Cytokine mRNA levels expressed by stimulated PBMC corresponded significantly to supernatant protein concentrations. Compared to the pre-treatment gene profile, post-treatment gene expression showed higher levels of CD4 and IFNgamma and a decreased abundance of the TGFbeta1 transcript.

CONCLUSION

In vitro we found that qrt-PCR can determine accurately immune cell density and CK gene profiles in tumor biopsies. In vivo findings support the hypothesis that, after TNFalpha-based treatment, a Th1-type shift occurs in the tumor microenvironment.

Correlation of serum IL-2, IL-6 and IL-10 levels with International Prognostic Index in patients with aggressive non-Hodgkin's lymphoma

Cytokines play important roles in the pathogenesis of lymphomas. The aim of this study was to determine the relations between serum levels of interleukin-2 (IL-2), IL-6, and IL-10 and parameters of International Prognostic Index (IPI). Serum levels of IL-2, IL-6, and IL-10 were measured using a sensitive enzyme-linked immunosorbent assay in the pretreatment frozen sera from 43 patients with non-Hodgkin's lymphoma. The patients we included in the study were divided into two groups, one with high risk and the other with low risk according to the IPI in regard to their ages, stages, performance status, extranodal involvements, and serum levels of lactate dehydrogenase. In the high-risk group, serum levels of IL-2 (0.852 +/- 0.268 ng/ml), IL-6 (0.461 +/- 0.206 ng/ml), and IL-10 (0.816 +/- 0.240 ng/ml) were found to be higher than serum levels of IL-2 (0.667 +/- 0.170 ng/ml), IL-6 (0.355 +/- 0.075 ng/ml), and IL-10 (0.643+0.177 ng/ml) in the low-risk group ( < 0.05). There was a correlation between the patients with high risk according to the IPI criteria and high levels of serum cytokines (IL-2, IL-6, IL-10). Knowledge of the serum levels of these cytokines in patients with newly diagnosed aggressive non-Hodgkin's lymphoma may help us to have some information about the possible prognosis, the activation of disease, and to decide on appropriate therapeutic approaches for individual patients.

Disruption of hematopoiesis and thymopoiesis in the early premalignant stages of infection with SL3-3 murine leukemia virus

A time course analysis of SL3-3 murine leukemia virus (SL3) infection in thymus and bone marrow of NIH/Swiss mice was performed to assess changes that occur during the early stages of progression to lymphoma. Virus was detectable in thymocytes, bone marrow, and spleen as early as 1 to 2 weeks postinoculation (p.i.). In bone marrow, virus infection was detected predominantly in immature myeloid or granulocytic cells. Flow cytometry revealed significant reductions of the Ter-119(+) and Mac-1(+) populations, and significant expansions of the Gr-1(+) and CD34(+) populations, between 2 and 4 weeks p.i. Analysis of colony-forming potential confirmed these findings. In the thymus, SL3 replication was associated with significant disruption in thymocyte subpopulation distribution between 4 and 7 weeks p.i. A significant thymic regression was observed just prior to the clonal outgrowth of tumor cells. Proviral long terminal repeats (LTRs) with increasing numbers of enhancer repeats were observed to accumulate exclusively in the thymus during the first 8 weeks p.i. Observations were compared to the early stages of infection with a virtually nonpathogenic SL3 mutant, termed SL3DeltaMyb5, which was shown by real-time PCR to be replication competent. Comparison of SL3 with SL3DeltaMyb5 implicated certain premalignant changes in tumorigenesis, including (i) increased proportions of Gr-1(+) and CD34(+) bone marrow progenitors, (ii) a significant increase in the proportion of CD4(-) CD8(-) thymocytes, (iii) thymic regression prior to tumor outgrowth, and (iv) accumulation of LTR enhancer variants. A model in which disrupted bone marrow hematopoiesis and thymopoiesis contribute to the development of lymphoma in the SL3-infected animal is discussed.

The contribution of NF-kappa B activity to spontaneous proliferation and resistance to apoptosis in human T-cell leukemia virus type 1 Tax-induced tumors

Human T-cell leukemia virus type I is the etiologic agent of adult T-cell leukemia/lymphoma. The Tax protein of this virus is thought to contribute to cellular transformation and tumor development. In this report, we have used a Tax transgenic mouse model of tumorigenesis to study the contribution of nuclear factor (NF)-kappa B activity to spontaneous tumor cell proliferation and resistance to apoptosis. We have demonstrated elevated expression levels of NF-kappa B--inducible cytokines, including interleukin (IL)-6, IL-10, IL-15, and interferon (IFN)-gamma, in freshly isolated primary tumors from Tax transgenic mice. Inhibitors of NF-kappa B activity, sodium salicylate and cyclopentenone prostaglandins (prostaglandin A(1) and 15-deoxy-Delta(12,14)-prostaglandin J(2)), blocked spontaneous proliferation of Tax transgenic mouse spleen cells. In addition, Tax-induced tumor cells, which are resistant to irradiation-induced apoptosis, became sensitive to apoptosis in the presence of sodium salicylate and prostaglandins. These results strongly suggest that Tax-mediated induction of NF-kappa B activity contributes to tumorigenesis in vivo. (Blood. 2001;98:1200-1208)

Tissue distribution and timing of appearance of polytropic envelope recombinants during infection with SL3-3 murine leukemia virus or its weakly pathogenic SL3DeltaMyb5 mutant

A time course analysis was performed to identify the sites of formation and timing of appearance of polytropic recombinant viruses following infection of NIH/Swiss mice with the murine retrovirus SL3-3 murine leukemia virus (SL3) or with a weakly pathogenic mutant termed SL3DeltaMyb5. The results indicated that (i) polytropic recombinant viruses occur initially in the thymus of SL3-infected animals, (ii) the timing of appearance of polytropic recombinants in bone marrow is not consistent with their participation in the previously reported formation of transplantable tumor-forming cells at 3 to 4 week postinoculation, and (iii) the efficient generation of recombinant virus is correlated with efficient tumor induction.