| 1. |
- Finnberg, Niklas
(författare)
-
The attenuation of the P53 response to DNA damage in rodent liver preneoplastic enzyme-altered foci
- 2003
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In connection with life-time bioassays in rodents, the liver is one of the organs most frequently affected. During the carcinogenic process, single preneoplastic hepatocytes develop into hepatocellular adenoma or carcinoma (HCC). Preneoplastic hepatocytes are identified on the basis of their overexpression of the inactivating phase 11 enzyme glutathione - S-transferase Pi (GST-P). In the presence of continuos exposure to carcinogen, initiated hepatocytes expand clonally to form hepatic enzyme-altered foci (EAF). Such development of EAF might be considered to be an adaptive response and their pattern of gene expression may provide mechanistic information concerning the action of a putative carcinogen. Our studies have focused on the response of the tumor suppressor p53 to DNA damage in EAR Activated by several types of cellular stress, the p53 protein is involved in regulating cell cycle arrest and apoptosis. The overall aim of our project was to characterize the attenuated p53 response to DNA damage in preneoplastic EAF lesions and the possible role of this attenuation in the development of EAF by diethylnitrosamine (DEN). To this end, after receiving an initiating neonatal dos of DEN female Sprague-Dawley rats were exposed to DEN or the non-genotoxic agent phenobarbital (PB), which induced the development of EAF in both cases. A challenging dose of DEN was also administered 24 hours prior to sacrifice to elicit a p53 response in these EAF. Only EAF arising from treatment with DEN exhibited an attenuated p53 response in comparison to that of surrounding, non-EAF tissue and PB-induced EAF. This attenuation was enhanced by prolonging the period of treatment, as well as in larger EAF. The attenuated p53 response to DEN-induced DNA damage was also present in primary co-cultures of hepatocytes isolated from EAF (GST -P -positive hepatocytes) and from non-EAF tissue (GST-P-negative hepatocytes). Treatment of such co-cultures with CoCl2, which mimics hypoxia, resulted in nuclear accumulation of p53 in the GST-P-positive cells. This finding demonstrates that a p53 response may be evoked by hypoxic stress, but not by genotoxic chemicals. Additional studies with the P13 kinase inhibitors caffeine and wortmannin, as well as with ATM antisense oligonucleotides indicated that ATM is involved in signalling to p53 following DEN-induced damage of DNA. Immunohistochemical analysis of the livers of DEN-treated rats and Western blotting of macroscopic EAF tissue revealed lowered expression of ATM in these tissues. Thus, down-regulation of ATM may to some extent explain the attenuated p53 response to DEN exhibited by EAT. Upon examining the combined p53-MDM2 response in rat liver at different time-points following a single injection of DEN, significant temporal and spatial variations were observed. Midzonal areas demonstrated a transient combined p53 - MDM2 response 6 - 24 hours after the DEN challenge, whereas in centrilobular areas this response culminated 24 - 72 hours after injection. MDM2 was constitutively expressed in midzonal areas. Furthermore, following repeated treatment with low doses of DEN, GST -P -positive EAF were found to be particularly prevalent in this same zone. Finally, the influence of the p53 gene dosage on the development of p53-negative preneoplastic lesions was investigated. Treatment of p53 (+/+) and (+/-) mice for 15 - 20 weeks with DEN revealed a genotype - dependent difference in the numbers of p53-negative preneoplastic hepatic lesions obtained, with p53 (+/-) mice developing significantly fewer p53 -negative lesions than p53 wild-type (+/+) mice. However, the total number and average size of all preneoplastic lesions were similar in these two types of mice. In conclusion, these findings indicate that an attenuated p53 response to DNA damage confers a growth advantage on preneoplastic focal lesions in the liver. The selective pressure for focal lesions exhibiting such p53 attenuation can be modulated by altering the p53 gene dosage or by exposure to xenobiotics. These observations indicate that the attenuated p53 response in preneoplastic lesions is an adaptive response to genotoxic stress.
|
|
| 2. |
- Kerzeli, Iliana K., et al.
(författare)
-
MALT1 inhibition suppresses antigen-specific T cell responses
- 2024
-
Ingår i: Cellular Immunology. - : Elsevier. - 0008-8749 .- 1090-2163. ; 397
-
Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to assess the potential use of a selective small molecule MALT1 inhibitor in solid tumor treatment as an immunotherapy targeting regulatory T-cells (Tregs). In vitro, MALT1 inhibition suppressed the proteolytic cleavage of the MALT1-substrate HOIL1 and blocked IL-2 secretion in Jurkat cells. It selectively suppressed the proliferation of PBMC-derived Tregs, with no effect on conventional CD4+ T-cells. In vivo, however, no evident anti-tumor effect was achieved by MALT1 inhibition monotherapy or in combination with anti-CTLA4 in the MB49 cancer model. Despite decreased Treg-frequencies in lymph nodes of tumor-bearing animals, intratumoral Treg depletion was not observed. We also showed that MALT1-inhibition caused a reduction of antigen-specific CD8+ T-cells in an adoptive T-cell transfer model. Thus, selective targeting of Tregs would be required to improve the immunotherapeutic effect of MALT1-inhibition. Also, various dosing schedules and combination therapy strategies should be carefully designed and evaluated further.
|
|
| 3. |
- Kerzeli, Iliana Kyriaki, et al.
(författare)
-
MALT1 inhibition suppresses T-cell dependent immune surveillance
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- MALT1 supports the development of natural regulatory T cells (Tregs), while protease-dead MALT1 (MALT1-PD) mice develop autoimmunity and an intrinsic capacity to reject syngeneic tumor transplantation. Herein, a small molecule inhibitor targeting MALT1 was developed and evaluated for potential use in Treg inhibition as part of a cancer immunotherapy strategy.In vitro, MALT1 inhibitor treatment inhibited the proteolytic cleavage of the MALT1 substrate HOIL1 in Jurkat cells and blocked IL-2 secretion by immune cells. Moreover, orally administrated MV088428 inhibited anti-CD3 induced IL-2 release in vivo. In vitro MALT1 inhibition selectively suppressed the proliferation of PBMC derived CD25+ FoxP3+ CD4+ T cells, while no direct effect was noted on the proliferation and viability of CD25- CD4+ T cells. In vivo, no evident anti-tumor effect as a monotherapy in the MB49 bladder cancer model was achieved and despite selective decrease of Treg frequencies in lymph nodes of tumor bearing animals, intratumoral Treg depletion was not observed. No synergistic anti-tumor effects were noted when MALT1 inhibitor was combined with anti-PD1 therapy, and concomitant treatment with MALT1 inhibitor abrogated the efficacy of anti-CTLA4 therapy. MALT1 inhibition had no impact on the frequencies of viable NK, lymphocyte and myeloid cells or on proliferation of conventional CD4 and CD8 T cells. However, there was a significant decrease of antigen-specific T cells in vivo upon adoptive T cell transfer and peptide vaccination. Thus, while MALT1 inhibition substantially reduced Treg populations in lymph nodes, but less so in tumors, off-target effects on antigen-experienced T cells along with the lack of impact on tumor Tregs likely abolish the compound’s efficacy. The off-target effect on antigen-experienced T cells could present implications for the use of MALT1 inhibitors for cancer indications where tumor control is likely to be mediated via T cell driven immune surveillance. Thus, dosing length and combination therapy strategies should be carefully designed and evaluated further.
|
|
