Inhibition of the ATR kinase enhances 5-FU sensitivity independently of nonhomologous end-joining and homologous recombination repair pathways

The epigenetic modifier HDAC2 and the checkpoint kinase ATM determine the responses of microsatellite instable colorectal cancer cells to 5-fluorouracil

The epigenetic modifier histone deacetylase-2 (HDAC2) is frequently dysregulated in colon cancer cells. Microsatellite instability (MSI), an unfaithful replication of DNA at nucleotide repeats, occurs in about 15% of human colon tumors. MSI promotes a genetic frameshift and consequently a loss of HDAC2 in up to 43% of these tumors. We show that long-term and short-term cultures of colorectal cancers with MSI contain subpopulations of cells lacking HDAC2. These can be isolated as single cell-derived, proliferating populations. Xenografted patient-derived colon cancer tissues with MSI also show variable patterns of HDAC2 expression in mice. HDAC2-positive and HDAC2-negative RKO cells respond similarly to pharmacological inhibitors of the class I HDACs HDAC1/HDAC2/HDAC3. In contrast to this similarity, HDAC2-negative and HDAC2-positive RKO cells undergo differential cell cycle arrest and apoptosis induction in response to the frequently used chemotherapeutic 5-fluorouracil, which becomes incorporated into and damages RNA and DNA. 5-fluorouracil causes an enrichment of HDAC2-negative RKO cells in vitro and in a subset of primary colorectal tumors in mice. 5-fluorouracil induces the phosphorylation of KAP1, a target of the checkpoint kinase ataxia-telangiectasia mutated (ATM), stronger in HDAC2-negative cells than in their HDAC2-positive counterparts. Pharmacological inhibition of ATM sensitizes RKO cells to cytotoxic effects of 5-fluorouracil. These findings demonstrate that HDAC2 and ATM modulate the responses of colorectal cancer cells towards 5-FU.

Efficient chemosensitizing and antimetastatic combinations of a naturally occurring trans-ferulic acid with different chemotherapies on an in vitro hepatocellular carcinoma model

Trans-ferulic acid (TFA) is a polyphenolic compound present in many dietary supplements. The aim of this study was to get better chemotherapeutic outcomes through treatment protocols for human hepatocellular carcinoma (HCC). This study focused on the exploration of the in vitro influence of a combination of TFA with 5-fluorouracil (5-FU), doxorubicin (DOXO), and cisplatin (CIS) on HepG2 cell line. Treatment with 5-FU, DOXO, and CIS alone down-regulated oxidative stress and alpha-fetoprotein (AFP), and decreased cell migration through the depression of metalloproteinases (MMP-3, MMP-9, and MMP-12) expression. Co-treatment with TFA synergized the effects of these chemotherapies by decreased MMP-3, MMP-9, and MMP-12 expression, and gelatinolytic activity of both MMP-9 and MMP-2 in cancer cells. TFA significantly reduced the elevated levels of AFP and NO, and depressed cell migration ability (metastasis) in HepG2 groups. Co-treatment with TFA elevated the chemotherapeutic potency of 5-FU, DOXO, and CIS in managing HCC.

Colon cancer organoids using monoclonal organoids established in four different lesions of one cancer patient reveal tumor heterogeneity and different real-time responsiveness to anti-cancer drugs

Organoid culture technique has been taking center stage as a next-generation ex-vivo model due to advancement of stem cell research techniques. The importance of the laboratory-based ex vivo model has increasingly been recognized for recapitulating histological, and physioglocal conditions of in vivo microenviorment. Accordingly, the use of this technique has also broadened the understanding of intratumoral heterogeneity which is closely associated with varied drug responses observed in patients. Likewise, studies on heterogeneity within a single tumor tissue have drawn much attention. Here, we isolated 15 single clones from 4 tumor organoid lines from 1 patient at a primary passage from one patient. Each organoid line showed variable alterations in both genotype and phenotype. Furthermore, our methodological approach on drug test employing a high-throughput screening system enabled us to pinpoint the optimal time frame for anti-cancer drugs within a single tumor. We propose that our method can effectively reveal the heterogeneity of time-point in drug response, and the most optimal therapeutic strategies for individual patient.

ATR inhibition sensitizes liposarcoma to doxorubicin by increasing DNA damage

Liposarcomas account for approximately 20% of all adult sarcomas and have limited therapeutic options outside of surgery. Inhibition of ataxia-telangiectasia and Rad3 related protein kinase (ATR) has emerged as a promising chemotherapeutic strategy in various cancers. However, its activation, expression, and function in liposarcoma remain unkown. In this study, we investigated the expression, function, and potential of ATR as a therapeutic target in liposarcoma. Activation and expression of ATR in liposarcoma was analyzed by immunohistochemistry, which was further explored for correlation with patient clinical characteristics. ATR-specific siRNA and the ATR inhibitor VE-822 were applied to determine the effect of ATR inhibition on liposarcoma cell proliferation and anti-apoptotic activity. Migration activity and clonogenicity were examined using wound healing and clonogenic assays. ATR (p-ATR) was overexpressed in 88.1% of the liposarcoma specimens and correlated with shorter overall survival in patients. Knockdown of ATR via specific siRNA or inhibition with VE-822 suppressed liposarcoma cell growth, proliferation, migration, colony-forming ability, and spheroid growth. Importantly, ATR inhibition significantly and synergistically enhanced liposarcoma cell line chemosensitivity to doxorubicin. Our findings support ATR as critical to liposarcoma proliferation and doxorubicin resistance. Therefore, the addition of ATR inhibition to a standard doxorubicin regimen is a potential treatment strategy for liposarcoma.

DNA damage response- and JAK-dependent regulation of PD-L1 expression in head and neck squamous cell carcinoma (HNSCC) cells exposed to 5-fluorouracil (5-FU)

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PD-L1 is an important immune checkpoint molecule expressed by HNSCC.

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5-FU induces PD-L1 expression in HNSCC cells.

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PD-L1 upregulation is DNA damage Response- and JAK-dependent.

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5-FU potentiates the effect of the inflammatory cytokine Ifn-γ.

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Targeting EGFR with cetuximab blunts PD-L1 expression induced by 5-FU.

Objectives

The immune checkpoint molecule PD-L1 (CD274) is a crucial regulator of the tumor immune response. Its expression has been reported in the therapeutic context in Head and Neck Squamous Cell Carcinoma (HNSCC), but it remains unclear how therapeutically approved molecules regulate PD-L1 expression in HNSCC cells.

Materials and methods

Three HNSCC cell lines (BICR6, PE/CA-PJ34 and PE/CA-PJ41) were used to analyze PD-L1 expression by immunoblotting, immunofluorescence and QPCR. Freely-available single cell RNAseq data from HNSCC were also used.

Results

5-Fluorouracil (5-FU) increased the expression of PD-L1 with high efficacy in HNSCC cells. Single cell RNAseq data suggested the specificity of the regulation of PD-L1 in this context. The effect of 5-FU on PD-L1 expression was related to its genotoxic effect and was prevented by extracellular application of thymidine or using a chemical inhibitor of the DNA damage Response kinases ATM/ATR. We found that the effect of 5-FU was additive or synergistic with IFN-γ, the canonical inducer of PD-L1 in epithelial cells. QPCR analysis confirmed this finding and identified JAK-dependent transcriptional activation of PD-L1/CD274 as the underlying mechanism. The induction of PD-L1 by 5-FU was partially prevented by Epidermal Growth Factor Receptor (EGFR) inhibition with cetuximab.

Conclusion

Our study highlights the specific DNA Damage Response- and JAK- dependent induction of PD-L1 by 5-FU in HNSCC cells. This induction is regulated by the cytokine context and is potentially therapeutically actionable.