TY  - JOUR
A1  - Fischer, Thomas
A1  - Hartmann, Oliver
A1  - Reissland, Michaela
A1  - Prieto-Garcia, Cristian
A1  - Klann, Kevin
A1  - Pahor, Nikolett
A1  - Schülein-Völk, Christina
A1  - Baluapuri, Apoorva
A1  - Polat, Bülent
A1  - Abazari, Arya
A1  - Gerhard-Hartmann, Elena
A1  - Kopp, Hans-Georg
A1  - Essmann, Frank
A1  - Rosenfeldt, Mathias
A1  - Münch, Christian
A1  - Flentje, Michael
A1  - Diefenbacher, Markus E.
T1  - PTEN mutant non-small cell lung cancer require ATM to suppress pro-apoptotic signalling and evade radiotherapy
JF  - Cell & Bioscience
N2  - Background
Despite advances in treatment of patients with non-small cell lung cancer, carriers of certain genetic alterations are prone to failure. One such factor frequently mutated, is the tumor suppressor PTEN. These tumors are supposed to be more resistant to radiation, chemo- and immunotherapy.

Results
We demonstrate that loss of PTEN led to altered expression of transcriptional programs which directly regulate therapy resistance, resulting in establishment of radiation resistance. While PTEN-deficient tumor cells were not dependent on DNA-PK for IR resistance nor activated ATR during IR, they showed a significant dependence for the DNA damage kinase ATM. Pharmacologic inhibition of ATM, via KU-60019 and AZD1390 at non-toxic doses, restored and even synergized with IR in PTEN-deficient human and murine NSCLC cells as well in a multicellular organotypic ex vivo tumor model.

Conclusion
PTEN tumors are addicted to ATM to detect and repair radiation induced DNA damage. This creates an exploitable bottleneck. At least in cellulo and ex vivo we show that low concentration of ATM inhibitor is able to synergise with IR to treat PTEN-deficient tumors in genetically well-defined IR resistant lung cancer models.
KW  - PTEN
KW  - ATM
KW  - IR
KW  - NSCLC
KW  - radiotherapy
KW  - cancer
KW  - DNA-PK
KW  - PI3K
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-299865
SN  - 2045-3701
VL  - 12
ER  - 
TY  - JOUR
A1  - Djuzenova, Cholpon S.
A1  - Fischer, Thomas
A1  - Katzer, Astrid
A1  - Sisario, Dmitri
A1  - Korsa, Tessa
A1  - Streussloff, Gudrun
A1  - Sukhorukov, Vladimir L.
A1  - Flentje, Michael
T1  - Opposite effects of the triple target (DNA-PK/PI3K/mTOR) inhibitor PI-103 on the radiation sensitivity of glioblastoma cell lines proficient and deficient in DNA-PKcs
JF  - BMC Cancer
N2  - Background: Radiotherapy is routinely used to combat glioblastoma (GBM). However, the treatment efficacy is often limited by the radioresistance of GBM cells.

Methods: Two GBM lines MO59K and MO59J, differing in intrinsic radiosensitivity and mutational status of DNA-PK and ATM, were analyzed regarding their response to DNA-PK/PI3K/mTOR inhibition by PI-103 in combination with radiation. To this end we assessed colony-forming ability, induction and repair of DNA damage by gamma H2AX and 53BP1, expression of marker proteins, including those belonging to NHEJ and HR repair pathways, degree of apoptosis, autophagy, and cell cycle alterations.

Results: We found that PI-103 radiosensitized MO59K cells but, surprisingly, it induced radiation resistance in MO59J cells. Treatment of MO59K cells with PI-103 lead to protraction of the DNA damage repair as compared to drug-free irradiated cells. In PI-103-treated and irradiated MO59J cells the foci numbers of both proteins was higher than in the drug-free samples, but a large portion of DNA damage was quickly repaired. Another cell line-specific difference includes diminished expression of p53 in MO59J cells, which was further reduced by PI-103. Additionally, PI-103-treated MO59K cells exhibited an increased expression of the apoptosis marker cleaved PARP and increased subG1 fraction. Moreover, irradiation induced a strong G2 arrest in MO59J cells (similar to 80% vs. similar to 50% in MO59K), which was, however, partially reduced in the presence of PI-103. In contrast, treatment with PI-103 increased the G2 fraction in irradiated MO59K cells.

Conclusions: The triple-target inhibitor PI-103 exerted radiosensitization on MO59K cells, but, unexpectedly, caused radioresistance in the MO59J line, lacking DNA-PK. The difference is most likely due to low expression of the DNA-PK substrate p53 in MO59J cells, which was further reduced by PI-103. This led to less apoptosis as compared to drug-free MO59J cells and enhanced survival via partially abolished cell-cycle arrest. The findings suggest that the lack of DNA-PK-dependent NHEJ in MO59J line might be compensated by DNA-PK independent DSB repair via a yet unknown mechanism.
KW  - DNA damage
KW  - DNA-PK
KW  - Histone gamma H2AX
KW  - p53
KW  - Radiation sensitivity
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-265826
VL  - 21
ER  -