Anti-Proliferative Effect of Radiotherapy and Implication of Immunotherapy in Anaplastic Thyroid Cancer Cells.

Radiotherapy and immunotherapy have shown promising efficacy for the treatment of solid malignancies. Here, we aim to clarify the potential of a combined application of radiotherapy and programmed cell death-ligand 1 (PD-L1) monoclonal antibody atezolizumab in primary anaplastic thyroid cancer (ATC) cells. The radiation caused a significant reduction in cell proliferation, measured by luminescence, and of the number of colonies.

Dual PI3K/mTOR Inhibitor NVP-BEZ235 Leads to a Synergistic Enhancement of Cisplatin and Radiation in Both HPV-Negative and -Positive HNSCC Cell Lines.

The standard of care for advanced head and neck cancers (HNSCCs) is radiochemotherapy, including cisplatin. This treatment results in a cure rate of approximately 85% for oropharyngeal HPV-positive HNSCCs, in contrast to only 50% for HPV-negative HNSCCs, and is accompanied by severe side effects for both entities. Therefore, innovative treatment modalities are required, resulting in a better outcome for HPV-negative HNSCCs, and lowering the adverse effects for both entities.

IL1 Pathway in HPV-Negative HNSCC Cells Is an Indicator of Radioresistance After Photon and Carbon Ion Irradiation Without Functional Involvement.

Background: Treatment of locally advanced HPV-negative head and neck squamous cell carcinoma (HNSCC) with photon radiation is the standard of care but shows only moderate success. Alterations in response toward DNA DSB repair, apoptosis, and senescence are underlying determinants of radioresistance in the tumor cells. Recently, senescence and the associated secretory phenotype (SASP) came into the focus of research and raised the need to identify the tumor-promoting molecular mechanisms of the SASP.

Establishment of a Transformation Coupled End Joining Assay to Estimate Radiosensitivity in Tumor Cells.

Here, we present a modified end-joining () assay to quantify EJ capacity, accuracy as well as pathway switch to alternative end-joining (Alt-EJ) or single strand annealing (SSA). A novel transformation assay was established to specifically measure circular repair products, which correlate with classical EJ efficiency. The assay was validated using EJ-deficient mammalian cell lines (Ku80, DNA-PKcs, LigIV, or XRCC4 mutants).

HPV-positive HNSCC cell lines show strongly enhanced radiosensitivity after photon but not after carbon ion irradiation.

Background And Purpose: HPV positive (pos.) HNSCC cells are significantly more radiosensitive to photon irradiation as compared to HPV negative (neg.) cells.

Dual PI3K/mTOR Inhibitor NVP-BEZ235 Enhances Radiosensitivity of Head and Neck Squamous Cell Carcinoma (HNSCC) Cell Lines Due to Suppressed Double-Strand Break (DSB) Repair by Non-Homologous End Joining.

The PI3K/Akt/mTOR pathway is frequently altered in human papillomavirus (HPV)-positive and negative squamous cell carcinoma of the head and neck (HNSCC) and overstimulation is associated with poor prognosis. PI3K drives Akt activation and constitutive signaling acts pro-proliferative, supports cell survival, DNA repair, and contributes to radioresistance. Since the small molecule NVP-BEZ235 (BEZ235) is a potent dual inhibitor of this pathway, we were interested whether BEZ235 could be an efficient radiosensitizer.

HPV-negative and HPV-positive HNSCC cell lines show similar numerical but different structural chromosomal aberrations.

Background: It was tested whether the difference in carcinogenesis between noxa and human papillomavirus (HPV)-driven head and neck squamous cell carcinoma (HNSCC) is associated with a variation in genomic instability.

Methods: Conventional and molecular cytogenetics in HPV-positive and HPV-negative HNSCC cell lines.

Results: Numerical aneuploidy determined by multicolor fluorescence in situ hybridization and DNA ploidy was very similar for both entities with most chromosomes being present either in quadruplicate or triplicate, and only few are still diploid with, however, a striking similarity in the overall pattern.

In HPV-Positive HNSCC Cells, Functional Restoration of the p53/p21 Pathway by Proteasome Inhibitor Bortezomib Does Not Affect Radio- or Chemosensitivity.

Human papillomavirus (HPV) associated squamous cell carcinomas of the head and neck region (HPV+ HNSCCs) harbor diverging biological features as compared to classical noxa-induced (HPV-) HNSCC. One striking difference between subtypes is that the tumor suppressor gene TP53 is usually not mutated in HPV+ HNSCCs. However, p53 is inhibited by viral oncoprotein E6, leading to premature proteasomal degradation.

Loss of causes DNA repair defects and enhances prostate cancer therapeutic responsiveness.

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Targeting CREB-binding protein overrides LPS induced radioresistance in non-small cell lung cancer cell lines.

Non-small cell lung cancer (NSCLC) has a very poor prognosis even when treated with the best therapies available today often including radiation. NSCLC is frequently complicated by pulmonary infections which appear to impair prognosis as well as therapy, whereby the underlying mechanisms are still not known. It was investigated here, whether the bacterial lipopolysaccharides (LPS) might alter the tumor cell radiosensitivity.

BCL2-overexpressing prostate cancer cells rely on PARP1-dependent end-joining and are sensitive to combined PARP inhibitor and radiation therapy.

Here we report that BCL2 blocks DNA double strand break (DSB) repair via nonhomologous end-joining (NHEJ), through sequestration of KU80 protein outside the nucleus. We find that this effect is associated with a repair switch to the error-prone PARP1-dependent end-joining (PARP1-EJ). We present in-vitro proof-of-concept for therapeutic targeting of this switch using PARP inhibitor to specifically enhance the radiosensitivity of BCL2-overexpressing cells.

Roscovitine strongly enhances the effect of olaparib on radiosensitivity for HPV neg. but not for HPV pos. HNSCC cell lines.

At present, advanced stage human Papillomavirus (HPV) negative and positive head and neck squamous cell carcinoma (HNSCC) are treated by intense multimodal therapy that includes radiochemotherapy, which are associated with relevant side effects. Patients with HPV positive tumors possess a far better prognosis than those with HPV negative cancers. Therefore, new therapeutic strategies are needed to improve the outcome especially of the latter one as well as quality of life for all HNSCC patients.

In cancer cell lines inhibition of SCF/c-Kit pathway leads to radiosensitization only when SCF is strongly over-expressed.

Background And Purpose: The SCF/c-Kit pathway is often overexpressed in human tumors leading to an enhanced tumorigenesis, proliferation and migration. It was now tested for NSCLC and prostate cancer cells growing in 2D and 3D whether the inhibition of this pathway can be used to achieve a significant radiosensitization and whether a respective biomarker may be identified.

Material And Methods: Experiments were performed with different cancer cell lines (NSCLC: H23, H520, H226, H1975 and PrCa: DU145) growing either under 2D or 3D conditions.

Loss of CHD1 causes DNA repair defects and enhances prostate cancer therapeutic responsiveness.

The CHD1 gene, encoding the chromo-domain helicase DNA-binding protein-1, is one of the most frequently deleted genes in prostate cancer. Here, we examined the role of CHD1 in DNA double-strand break (DSB) repair in prostate cancer cells. We show that CHD1 is required for the recruitment of CtIP to chromatin and subsequent end resection during DNA DSB repair.

Sorafenib inhibits cell growth but fails to enhance radio- and chemosensitivity of glioblastoma cell lines.

Background: Glioblastomas (GBM) are the most common malignant type of primary brain tumor. GBM are intensively treated with surgery and combined radiochemotherapy using X-irradiation and temozolomide (TMZ) but they are still associated with an extremely poor prognosis, urging for the development of new treatment strategies. To improve the outcome of GBM patients, the small molecule multi-kinase inhibitor sorafenib has moved into focus of recent research.

Impaired 53BP1/RIF1 DSB mediated end-protection stimulates CtIP-dependent end resection and switches the repair to PARP1-dependent end joining in G1.

End processing at DNA double strand breaks (DSB) is a decisive step in repair pathway selection. Here, we investigated the role of 53BP1/RIF1 in limiting BRCA1/CtIP-mediated end resection to control DSB repair pathway choice. ATM orchestrates this process through 53BP1 phosphorylation to promote RIF1 recruitment.

Radiosensitization of HNSCC cells by EGFR inhibition depends on the induction of cell cycle arrests.

The increase in cellular radiosensitivity by EGF receptor (EGFR) inhibition has been shown to be attributable to the induction of a G1-arrest in p53-proficient cells. Because EGFR targeting in combination with radiotherapy is used to treat head and neck squamous cell carcinomas (HNSCC) which are predominantly p53 mutated, we tested the effects of EGFR targeting on cellular radiosensitivity, proliferation, apoptosis, DNA repair and cell cycle control using a large panel of HNSCC cell lines. In these experiments EGFR targeting inhibited signal transduction, blocked proliferation and induced radiosensitization but only in some cell lines and only under normal (pre-plating) conditions.

Cancer cell motility is affected through 3D cell culturing and SCF/c-Kit pathway but not by X-irradiation.

Background And Purpose: Success of radiotherapy is often limited by therapy resistance and metastasis resulting from cancer cell motility. It was tested in vitro whether this cancer cell motility is affected by growth condition, active SCF/c-Kit pathway or X-irradiation.

Materials And Methods: Cell motility was measured with BioCoat™ Matrigel™ invasion chamber using four different cancer cell lines (NSCLC: H23, H520, H226 and PrCa: DU145).

Effect of sorafenib on cisplatin-based chemoradiation in head and neck cancer cells.

Despite aggressive chemoradiation (CRT) protocols in the treatment of patients with head and neck squamous cell carcinomas (HNSCC), the outcome is still unfavorable. To improve therapy efficacy we had already successfully tested the multikinase inhibitor sorafenib in combination with irradiation (IR) in previous studies on HNSCC cell lines. In this study we investigated its effect on combined CRT treatment using cisplatin.

Functional crosstalk between DNA damage response proteins 53BP1 and BRCA1 regulates double strand break repair choice.

Purpose: The aim of this study was to elucidate the impact of DNA damage response (DDR) proteins 53BP1 and BRCA1 on the double-strand break (DSB)-repair choice. This is important not only in order to understand the underlying mechanisms of DSB-repair pathway regulation but also to determine the therapeutic implications for BRCA1-associated tumors.

Materials And Methods: Human tumor cell lines A549 and HeLa were used.

Quantitative proteomics unveiled: Regulation of DNA double strand break repair by EGFR involves PARP1.

Background: EGFR inhibition blocks DNA double strand break (DSB) repair but the detailed mechanisms are still unclear. We asked whether EGFR inhibition blocks DSB repair by reducing the X-ray-induced phosphorylation of repair proteins using a phosphoproteomic approach.

Materials And Methods: Using UT-SCC5 and SAS head and neck cancer cells we established a differential phosphoproteomic approach for quantitative analysis of DNA repair proteins by stable isotope labeling with amino acids.

EGFRvIII does not affect radiosensitivity with or without gefitinib treatment in glioblastoma cells.

Background: Glioblastomas (GBM) are often characterized by an elevated expression of the epidermal growth factor receptor variant III (EGFRvIII). We used GBM cell lines with native EGFRvIII expression to determine whether this EGFR variant affects radiosensitivity with or without EGFR targeting.

Methods: Experiments were performed with GBM cell lines lacking (LN229, U87MG, U251, CAS-1) or endogenously expressing EGFRvIII (BS153, DKMG).

High levels of RAD51 perturb DNA replication elongation and cause unscheduled origin firing due to impaired CHK1 activation.

In response to replication stress ATR signaling through CHK1 controls the intra-S checkpoint and is required for the maintenance of genomic integrity. Homologous recombination (HR) comprises a series of interrelated pathways that function in the repair of DNA double strand breaks and interstrand crosslinks. In addition, HR, with its key player RAD51, provides critical support for the recovery of stalled forks during replication.

Radiosensitization of NSCLC cells by EGFR inhibition is the result of an enhanced p53-dependent G1 arrest.

Purpose: How EGF receptor (EGFR) inhibition induces cellular radiosensitization and with that increase in tumor control is still a matter of discussion. Since EGFR predominantly regulates cell cycle and proliferation, we studied whether a G1-arrest caused by EGFR inhibition may contribute to these effects.

Materials And Methods: We analyzed human non-small cell lung cancer (NSCLC) cell lines either wild type (wt) or mutated in p53 (A549, H460, vs.

The inhibition of PARP but not EGFR results in the radiosensitization of HPV/p16-positive HNSCC cell lines.

Background And Purpose: HPV-negative and HPV-positive HNSCC comprise distinct tumor entities with different biological characteristics. Specific regimens for the comparably well curable HPV-positive entity that reduce side effects without compromising outcome have yet to be established. Therefore, we tested here whether the inhibition of EGFR or PARP may be used to specifically enhance the radiosensitivity of HPV-positive HNSCC cells.