Establishment and characterization of cell lines from chromosomal instable colorectal cancer

Selective but not pan-CDK inhibition abrogates 5-FU-driven tissue factor upregulation in colon cancer

Thromboembolic events are complications in cancer patients and hypercoagulability has been linked to the tissue factor (TF) pathway, making this an attractive target. Here, we investigated the effects of chemotherapeutics and CDK inhibitors (CDKI) abemaciclib/palbociclib (CDK4/6), THZ-1 (CDK7/12/13), and dinaciclib (CDK1/2/5/9) alone and in combination regimens on TF abundance and coagulation. The human colorectal cancer (CRC) cell line HROC173 was treated with 5-FU or gemcitabine to stimulate TF expression. TF+ cells were sorted, recultured, and re-analyzed. The effect of treatment alone or in combination was assessed by functional assays. Low-dose chemotherapy induced a hypercoagulable state and significantly upregulated TF, even after reculture without treatment. Cells exhibited characteristics of epithelial-mesenchymal transition, including high expression of vimentin and mucin. Dinaciclib and THZ-1 also upregulated TF, while abemaciclib and palbociclib downregulated it. Similar results were observed in coagulation assays. The same anticoagulant activity of abemaciclib was seen after incubation with peripheral immune cells from healthy donors and CRC patients. Abemaciclib reversed 5-FU-induced TF upregulation and prolonged clotting times in second-line treatment. Effects were independent of cytotoxicity, senescence, and p27kip1 induction. TF-antibody blocking experiments confirmed the importance of TF in plasma coagulation, with Factor XII playing a minor role. Short-term abemaciclib counteracts 5-FU-induced hypercoagulation and eventually even prevents thromboembolic events.

Direct-Current Electrical Field Stimulation of Patient-Derived Colorectal Cancer Cells

Several cues for a directional migration of colorectal cancer cells were identified as being crucial in tumor progression. However, galvanotaxis, the directional migration in direct-current electrical fields, has not been investigated so far. Therefore, we asked whether direct-current electrical fields could be used to mobilize colorectal cancer cells along field vectors. For this purpose, five patient-derived low-passage cell lines were exposed to field strengths of 150-250 V/m in vitro, and migration along the field vectors was investigated. To further study the role of voltage-gated calcium channels on galvanotaxis and intracellular signaling pathways that are associated with migration of colorectal cancer cells, the cultures were exposed to selective inhibitors. In three out of five colorectal cancer cell lines, we found a preferred cathodal migration. The cellular integrity of the cells was not impaired by exposure of the cells to the selected field strengths. Galvanotaxis was sensitive to inhibition of voltage-gated calcium channels. Furthermore, signaling pathways such as AKT and MEK, but not STAT3, were also found to contribute to galvanotaxis in our in vitro model system. Overall, we identify electrical fields as an important contributor to the directional migration of colorectal cancer cells.

Establishment and Characterization of Novel Human Intestinal In Vitro Models for Absorption and First-Pass Metabolism Studies

Commonly used intestinal in vitro models are limited in their potential to predict oral drug absorption. They either lack the capability to form a tight cellular monolayer mimicking the intestinal epithelial barrier or the expression of cytochrome P450 3A4 (CYP3A4). The aim of this study was to establish a platform of colorectal cancer patient-derived cell lines for evaluation of human intestinal drug absorption and metabolism. We characterized ten 2D cell lines out of our collection with confluent outgrowth and long-lasting barrier forming potential as well as suitability for high throughput applications with special emphasis on expression and inducibility of CYP3A4. By assessment of the transepithelial electrical resistance (TEER) the cells barrier function capacity can be quantified. Very high TEER levels were detected for HROC60. A high basal CYP3A4 expression and function was found for HROC32. Eight cell lines showed higher CYP3A4 induction by stimulation via the vitamin D receptor compared to Caco-2 cells (5.1- to 16.8-fold change). Stimulation of the pregnane X receptor led to higher CYP3A4 induction in two cell lines. In sum, we identified the two cell lines HROC183 T0 M2 and HROC217 T1 M2 as useful tools for in vitro drug absorption studies. Due to their high TEER values and inducibility by drug receptor ligands, they may be superior to Caco-2 cells to analyze oral drug absorption and intestinal drug–drug interactions. Significance statement: Selecting appropriate candidates is important in preclinical drug development. Therefore, cell models to predict absorption from the human intestine are of the utmost importance. This study revealed that the human cell lines HROC183 T0 M2 and HROC217 T1 M2 may be better suited models and possess higher predictive power of pregnane X receptor- and vitamin D-mediated drug metabolism than Caco-2 cells. Consequently, they represent useful tools for predicting intestinal absorption and simultaneously enable assessment of membrane permeability and first-pass metabolism.

Preclinical Head and Neck Squamous Cell Carcinoma Models for Combined Targeted Therapy Approaches

This study aimed to refine combined targeted approaches on well-characterized, low-passage tumor models. Upon in vivo xenografting in immunodeficient mice, three cell lines from locally advanced or metastatic HNSCC were established. Following quality control and basic characterization, drug response was examined after therapy with 5-FU, Cisplatin, and cyclin-dependent kinase inhibitors (abemaciclib, THZ1). Our cell lines showed different in vitro growth kinetics, morphology, invasive potential, and radiosensitivity. All cell lines were sensitive to 5-FU, Cisplatin, and THZ1. One cell line (HNSCC48 P0 M1) was sensitive to abemaciclib. Here, Cyto-FISH revealed a partial CDKN2a deletion, which resulted from a R58* mutation. Moreover, this cell line demonstrated chromosome 12 polysomy, accompanied by an increase in CDK4-specific copy numbers. In HNSCC16 P1 M1, we likewise identified polysomy-associated CDK4-gains. Although not sensitive to abemaciclib per se, the cell line showed a G1-arrest, an increased number of acidic organelles, and a swollen structure. Notably, intrinsic resistance was conquered by Cisplatin because of cMYC and IDO-1 downregulation. Additionally, this Cisplatin-CDKI combination induced HLA-ABC and PD-L1 upregulation, which may enhance immunogenicity. Performing functional and molecular analysis on patient-individual HNSCC-models, we identified CDK4-gains as a biomarker for abemaciclib response prediction and describe an approach to conquer intrinsic CDKI resistance.

Microsatellite Status and IκBα Expression Levels Predict Sensitivity to Pharmaceutical Curcumin in Colorectal Cancer Cells

Simple Summary

The global burden of colorectal cancer is high. Chemotherapy has been the backbone of colorectal cancer therapy for decades. Toxic side effects and frequently occurring drug resistances remain challenging problems. Therefore, exploring natural compounds with low or even no toxicity holds great potential. However, natural curcumin is poorly absorbed, limiting its clinical use. Therefore, our focus was to screen different molecular types of colorectal cancer to find the ones with the highest sensitivity to curcumin. We observed very individual responses to curcumin for various colorectal cancer cell lines. Most curcumin-sensitive cell lines were of the microsatellite-stable molecular type, and expressed high baseline levels of the IκBα protein. Contrarily, curcumin-resistant lines were mainly microsatellite instable, with low baseline IκBα levels. Considering all of the data obtained, we conclude that patients with microsatellite-stable tumors and high baseline IκBα protein expression would benefit from treatment with novel curcumin formulations and derivatives.

Abstract

Clinical utilization of curcumin in colorectal cancer (CRC) was revived as a result of the development of novel curcumin formulations with improved bioavailability. Additionally, identification of biomarkers for curcumin sensitivity would also promote successful clinical applications. Here, we wanted to identify such biomarkers in order to establish a predictive model for curcumin sensitivity. Thirty-two low-passage CRC cell lines with specified tumor characteristics were included. Curcumin suppressed cell proliferation, yet sensitivity levels were distinct. Most curcumin-sensitive CRC cell lines were microsatellite stable and expressed high levels of IκBα. The predictive capacity of this biomarker combination possessed a statistical significance of 72% probability to distinguish correctly between curcumin-sensitive and -resistant CRC cell lines. Detailed functional analyses were performed with three sensitive and three resistant CRC cell lines. As curcumin’s mode of action, inhibition of NF-κB p65 activation via IκBα was identified. In consequence, we hypothesize that novel curcumin formulations—either alone or, more likely, in combination with standard therapeutics—can be expected to prove clinically beneficial for CRC patients with high IκBα expression levels.

The HROC-Xenobank-A High Quality Assured PDX Biobank of >100 Individual Colorectal Cancer Models

Simple Summary

Considering recent research, it was established that the best experimental models to conserve biological features of human tumors and to predict individual clinical treatment success are patient-derived xenografts (PDX). Their recognized and growing importance for translational research, especially for late-stage preclinical testing of novel therapeutics, necessitates a high number of well-defined PDX models from individual patients’ tumors. The starting platform for the Hansestadt Rostock colorectal cancer (HROC)-Xenobank was the assortment of colorectal tumor and normal tissue samples from patients stored in our university biobank.

Abstract

Based on our research group’s large biobank of colorectal cancers (CRC), we here describe the ongoing activity of establishing a high quality assured PDX biobank for more than 100 individual CRC cases. This includes sufficient numbers of vitally frozen (n > 30 aliquots) and snap frozen (n > 5) backups, “ready to use”. Additionally, PDX tumor pieces were paraffin embedded. At the current time, we have completed 125 cases. This resource allows histopathological examinations, molecular characterizations, and gene expression analysis. Due to its size, different issues of interest can be addressed. Most importantly, the application of low-passage, cryopreserved, and well-characterized PDX for in vivo studies guarantees the reliability of results due to the largely preserved tumor microenvironment. All cases described were molecularly subtyped and genetic identity, in comparison to the original tumor tissue, was confirmed by fingerprint analysis. The latter excludes ambiguity errors between the PDX and the original patient tumor. A cancer hot spot mutation analysis was performed for n = 113 of the 125 cases entities. All relevant CRC molecular subtypes identified so far are represented in the Hansestadt Rostock CRC (HROC)-Xenobank. Notably, all models are available for cooperative research approaches.

Preclinical models as patients' avatars for precision medicine in colorectal cancer: past and future challenges

Colorectal cancer (CRC) is a complex and heterogeneous disease, characterized by dismal prognosis and low survival rate in the advanced (metastatic) stage. During the last decade, the establishment of novel preclinical models, leading to the generation of translational discovery and validation platforms, has opened up a new scenario for the clinical practice of CRC patients. To bridge the results developed at the bench with the medical decision process, the ideal model should be easily scalable, reliable to predict treatment responses, and flexibly adapted for various applications in the research. As such, the improved benefit of novel therapies being tested initially on valuable and reproducible preclinical models would lie in personalized treatment recommendations based on the biology and genomics of the patient's tumor with the overall aim to avoid overtreatment and unnecessary toxicity. In this review, we summarize different in vitro and in vivo models, which proved efficacy in detection of novel CRC culprits and shed light into the biology and therapy of this complex disease. Even though cell lines and patient-derived xenografts remain the mainstay of colorectal cancer research, the field has been confidently shifting to the use of organoids as the most relevant preclinical model. Prioritization of organoids is supported by increasing body of evidence that these represent excellent tools worth further therapeutic explorations. In addition, novel preclinical models such as zebrafish avatars are emerging as useful tools for pharmacological interrogation. Finally, all available models represent complementary tools that can be utilized for precision medicine applications.

Patient-individual cancer cell lines and tissue analysis delivers no evidence of sequences from DNA viruses in colorectal cancer cells

Background

Several DNA viruses are highly suspicious to have oncogenic effects in humans. This study investigates the presence of potentially oncogenic viruses such as SV40, JCV, BKV and EBV in patient-derived colorectal carcinoma (CRC) cells typifying all molecular subtypes of CRC.

Methods

Sample material (gDNA and cDNA) of a total of 49 patient-individual CRC cell lines and corresponding primary material from 11 patients, including normal, tumor-derived and metastasis-derived tissue were analyzed for sequences of SV40, JVC, BKV and EBV using endpoint PCR. In addition, the susceptibility of CRC cells to JCV and BKV was examined using a long-term cultivation approach of patient-individual cells in the presence of viruses.

Results

No virus-specific sequences could be detected in all specimens. Likewise, no morphological changes were observed and no evidence for viral infection or integration could be provided after long term CRC cell cultivation in presence of viral particles.

Conclusions

In summary, the presented data suggest that there is no direct correlation between tumorigenesis and viral load and consequently no evidence for a functional role of the DNA viruses included into this analysis in CRC development.

Streptococcus gallolyticus abrogates anti-carcinogenic properties of tannic acid on low-passage colorectal carcinomas

The tannase-producing Gram-positive bacterial species Streptococcus gallolyticus subsp. gallolyticus (Sgg) is an opportunistic pathogen of the human gut and strongly associated with colorectal cancer (CRC). A unique feature of Sgg is its ability to degrade tannic acids (TA). TA constitute an important part of the human diet with known anti-tumorigenic properties. Here, we examined whether Sgg is able to protect tumor cells from the toxic effect of TA and thus drive tumorigenesis indirectly. Human CRC cell lines (n = 8) were treated with increasing concentrations of TA. We confirmed the cytotoxic activity of TA in a dose-dependent manner. In virtually all cell lines, viability decreased significantly (>60% inhibition). Moreover, pyrogallol, the degradation product of TA, had no effect on the tested cell lines. This suggests a specific effect of TA. Cytotoxicity was due to necrosis and induction of senescence in residual cells. Finally, when TA was degraded by Sgg, the cytotoxic effect could be abolished. Tumor cells even responded with boosted cell proliferation, highlighting the impact of Sgg on CRC progression. We here provide another piece of evidence for the active interplay between Sgg and cancer preventive components. These data will help to move forward in designing concepts for therapeutic and eventually also prophylactic approaches to combat gastrointestinal malignancies.

Targeting Immune-Related Molecules in Cancer Therapy: A Comprehensive In Vitro Analysis on Patient-Derived Tumor Models

This study investigated the impact of immune-related pathway inhibition, among them indolamine 2,3-dioxygenase (IDO), alone and together with immune cells on growth and viability of colorectal cancer (CRC) cells. A panel of patient-derived CRC cell lines with different molecular characteristics (CpG island methylator phenotype, chromosomal, and microsatellite instability) was included. Initial phenotyping of CRC cell lines (n=17) revealed high abundance of immunosuppressive checkpoint-molecules in general, but an individual profile for IDO. Presence of immune-related molecules was independent of the molecular subtype. Selective treatment of CRC cell lines showing high or low IDO expression (n=2 cell lines each) was performed with single agents and combinations of Indoximod, Curcumin, and Gemcitabine with and without the addition of peripheral blood lymphocytes (PBL) in an allogeneic setting. All substances affected CRC cell growth in a cell line specific manner. The combination of Curcumin and Gemcitabine proved to be most effective in tumor cell elimination. Functional read-out analyses identified cellular senescence, after both single and combined treatment. Curcumin alone exerted strong cytotoxic effects by inducing early and late apoptosis. Necrosis was not detectable at all. Addition of lymphocytes generally boosted antitumoral effects of all IDO-inhibitors, with up to 80 % cytotoxicity for the Curcumin treatment. Here, no obvious differences became apparent between individual cell lines. Combined application of Curcumin and low-dose chemotherapy is a promising strategy to kill tumor target cells and to stimulate antitumoral immune responses.

Establishment, functional and genetic characterization of three novel patient-derived rectal cancer cell lines

AIM

To establish patient-individual tumor models of rectal cancer for analyses of novel biomarkers, individual response prediction and individual therapy regimens.

METHODS

Establishment of cell lines was conducted by direct in vitro culturing and in vivo xenografting with subsequent in vitro culturing. Cell lines were in-depth characterized concerning morphological features, invasive and migratory behavior, phenotype, molecular profile including mutational analysis, protein expression, and confirmation of origin by DNA fingerprint. Assessment of chemosensitivity towards an extensive range of current chemotherapeutic drugs and of radiosensitivity was performed including analysis of a combined radio- and chemotherapeutic treatment. In addition, glucose metabolism was assessed with ¹⁸F-fluorodeoxyglucose (FDG) and proliferation with ¹⁸F-fluorothymidine.

RESULTS

We describe the establishment of ultra-low passage rectal cancer cell lines of three patients suffering from rectal cancer. Two cell lines (HROC126, HROC284Met) were established directly from tumor specimens while HROC239 T0 M1 was established subsequent to xenografting of the tumor. Molecular analysis classified all three cell lines as CIMP-0/ non-MSI-H (sporadic standard) type. Mutational analysis revealed following mutational profiles: HROC126: APC^wt, TP53^wt, KRAS^wt, BRAF^wt, PTEN^wt; HROC239 T0 M1: APC^mut, P53^wt, KRAS^mut, BRAF^wt, PTEN^mut and HROC284Met: APC^wt, P53^mut, KRAS^mut, BRAF^wt, PTEN^mut. All cell lines could be characterized as epithelial (EpCAM⁺) tumor cells with equivalent morphologic features and comparable growth kinetics. The cell lines displayed a heterogeneous response toward chemotherapy, radiotherapy and their combined application. HROC126 showed a highly radio-resistant phenotype and HROC284Met was more susceptible to a combined radiochemotherapy than HROC126 and HROC239 T0 M1. Analysis of ¹⁸F-FDG uptake displayed a markedly reduced FDG uptake of all three cell lines after combined radiochemotherapy.

CONCLUSION

These newly established and in-depth characterized ultra-low passage rectal cancer cell lines provide a useful instrument for analysis of biological characteristics of rectal cancer.

Establishment, functional and genetic characterization of a colon derived large cell neuroendocrine carcinoma cell line

AIM

To establish cell line and patient-derived xenograft (PDX) models for neuroendocrine carcinomas (NEC) which is highly desirable for gaining insight into tumor development as well as preclinical research including biomarker testing and drug response prediction.

METHODS

Cell line establishment was conducted from direct in vitro culturing of colonic NEC tissue (HROC57). A PDX could also successfully be established from vitally frozen tumor samples. Morphological features, invasive and migratory behavior of the HROC57 cells as well as expression of neuroendocrine markers were vastly analyzed. Phenotypic analysis was done by microscopy and multicolor flow cytometry. The extensive molecular-pathological profiling included mutation analysis, assessment of chromosomal and microsatellite instability; and in addition, fingerprinting (i.e., STR analysis) was performed from the cell line in direct comparison to primary patient-derived tissues and the PDX model established. Drug responsiveness was examined for a panel of chemotherapeutics in clinical use for the treatment of solid cancers.

RESULTS

The established cell line HROC57 showed distinct morphological and molecular features of a poorly differentiated large-cell NEC with KI-67 > 50%. Molecular-pathological analysis revealed a CpG island promoter methylation positive cell line with microsatellite instability being absent. The following mutation profile was observed: KRAS (wt), BRAF (mut). A high sensitivity to etoposide, cisplatin and 5-FU could be demonstrated while it was more resistant towards rapamycin.

CONCLUSION

We successfully established and characterized a novel patient-derived NEC cell line in parallel to a PDX model as a useful tool for further analysis of the biological characteristics and for development of novel diagnostic and therapeutic options for NEC.

Murine Endogenous Retroviruses Are Detectable in Patient-Derived Xenografts but Not in Patient-Individual Cell Lines of Human Colorectal Cancer

Endogenous retroviruses are remnants of retroviral infections. In contrast to their human counterparts, murine endogenous retroviruses (mERV) still can synthesize infectious particles and retrotranspose. Xenotransplanted human cells have occasionally been described to be mERV infected. With genetic engineered mice and patient-derived xenografts (PDXs) on the rise as eminent research tools, we here systematically investigated, if different tumor models harbor mERV infections. Relevant mERV candidates were first preselected by next generation sequencing (NGS) analysis of spontaneous lymphomas triggered by colorectal cancer (CRC) PDX tissue. Two primer systems were designed for each of these candidates (AblMLV, EcoMLV, EndoPP, MLV, and preXMRV) and implemented in an quantitative real-time (RT-qPCR) screen using murine tissues (n = 11), PDX-tissues (n = 22), PDX-derived cell lines (n = 13), and patient-derived tumor cell lines (n = 14). The expression levels of mERV varied largely both in the PDX samples and in the mouse tissues. No mERV signal was, however, obtained from cDNA or genomic DNA of CRC cell lines. Expression of EcoMLV was higher in PDX than in murine tissues; for EndoPP it was the opposite. These two were thus further investigated in 40 additional PDX. In addition, four patient-derived cell lines free of any mERV expression were subcutaneously injected into immunodeficient mice. Outgrowing cell-derived xenografts barely expressed EndoPP. In contrast, the expression of EcoMLV was even higher than in surrounding mouse tissues. This expression gradually vanished within few passages of re-cultivated cells. In summary, these results strongly imply that: (i) PDX and murine tissues in general are likely to be contaminated by mERV, (ii) mERV are expressed transiently and at low level in fresh PDX-derived cell cultures, and (iii) mERV integration into the genome of human cells is unlikely or at least a very rare event. Thus, mERVs are stowaways present in murine cells, in PDX tissues and early thereof-derived cell cultures. We conclude that further analysis is needed concerning their impact on results obtained from studies performed with PDX but also with murine tumor models.

β-catenin-independent regulation of Wnt target genes by RoR2 and ATF2/ATF4 in colon cancer cells

Wnt signaling is an evolutionarily conserved signaling route required for development and homeostasis. While canonical, β-catenin-dependent Wnt signaling is well studied and has been linked to many forms of cancer, much less is known about the role of non-canonical, β-catenin-independent Wnt signaling. Here, we aimed at identifying a β-catenin-independent Wnt target gene signature in order to understand the functional significance of non-canonical signaling in colon cancer cells. Gene expression profiling was performed after silencing of key components of Wnt signaling pathway and an iterative signature algorithm was applied to predict pathway-dependent gene signatures. Independent experiments confirmed several target genes, including PLOD2, HADH, LCOR and REEP1 as non-canonical target genes in various colon cancer cells. Moreover, non-canonical Wnt target genes are regulated via RoR2, Dvl2, ATF2 and ATF4. Furthermore, we show that the ligands Wnt5a/b are upstream regulators of the non-canonical signature and moreover regulate proliferation of cancer cells in a β-catenin-independent manner. Our experiments indicate that colon cancer cells are dependent on both β-catenin-dependent and –independent Wnt signaling routes for growth and proliferation.

Characterization of novel low passage primary and metastatic colorectal cancer cell lines

In vitro models are essential to understanding the molecular characteristics of colorectal cancer (CRC) and the testing of therapies for CRC. Many efforts to establish and characterize primary CRC cell lines have been published, most describing a small number of novel cell lines. However, there remains a lack of a large panel of uniformly established and characterized cell lines. To this end we established 20 novel CRC cell lines, of which six were derived from liver metastases. Genetic, genomic and transcriptomic profiling was performed in order to characterize these new cell lines. All data are made publically available upon publication.

By combining mutation profiles with CNA and gene expression profiles, we generated an overall profile of the alterations in the major CRC-related signaling pathways. The combination of mutation profiles with genome, transcriptome and methylome data means that these low passage cell lines are among the best characterized of all CRC cell lines. This will allow researchers to select model cell lines appropriate to specific experiments, facilitating the optimal use of these cell lines as in vitro models for CRC. All cell lines are available for further research.

Application of in vivo imaging techniques to monitor therapeutic efficiency of PLX4720 in an experimental model of microsatellite instable colorectal cancer

OBJECTIVES

Patient-derived tumor cell lines are a powerful tool to analyze the sensitivity of individual tumors to specific therapies in mice. An essential prerequisite for such an approach are reliable quantitative techniques to monitor tumor progression in vivo.

METHODS

We have employed HROC24 cells, grown heterotopically in NMRI Foxn1^nu mice, as a model of microsatellite instable colorectal cancer to investigate the therapeutic efficiencies of 5'-fluorouracil (5'-FU) and the mutant BRAF inhibitor PLX4720, a vemurafenib analogue, by three independent methods: external measurement by caliper, magnetic resonance imaging (MRI) and positron emission tomography/computed tomography (PET/CT) with 2-deoxy-2-(¹⁸F)fluoro-D-glucose (¹⁸F-FDG).

RESULTS

Repeated measure ANOVA by a general linear model revealed that time-dependent changes of anatomic tumor volumes measured by MRI differed significantly from those of anatomic volumes assessed by caliper and metabolic volumes determined by PET/CT. Over the investigation period of three weeks, neither 5'-FU, PLX4720 nor a combination of both drugs affected the tumor volumes. Also, there was no drug effect on the apparent diffusion constant (ADC) value as detected by MRI. Interestingly, however, PET/CT imaging showed that PLX4720-containing therapies transiently reduced the standardized uptake value (SUV), indicating a temporary response to treatment.

CONCLUSIONS

5'-FU and PLX4720 were largely ineffective with respect to HROC24 tumor growth. Tumoral uptake of ¹⁸F-FDG, as expressed by the SUV, proved as a sensitive indicator of small therapeutic effects. Metabolic imaging by ¹⁸F-FDG PET/CT is a suitable approach to detect effects of tumor-directed therapies early and even in the absence of morphological changes.

Reactivating p53 and Inducing Tumor Apoptosis (RITA) Enhances the Response of RITA-Sensitive Colorectal Cancer Cells to Chemotherapeutic Agents 5-Fluorouracil and Oxaliplatin

Colorectal carcinoma (CRC) is the most common cancer of the gastrointestinal tract with frequently dysregulated intracellular signaling pathways, including p53 signaling. The mainstay of chemotherapy treatment of CRC is 5-fluorouracil (5FU) and oxaliplatin. The two anticancer drugs mediate their therapeutic effect via DNA damage-triggered signaling. The small molecule reactivating p53 and inducing tumor apoptosis (RITA) is described as an activator of wild-type and reactivator of mutant p53 function, resulting in elevated levels of p53 protein, cell growth arrest, and cell death. Additionally, it has been shown that RITA can induce DNA damage signaling. It is expected that the therapeutic benefits of 5FU and oxaliplatin can be increased by enhancing DNA damage signaling pathways. Therefore, we highlighted the antiproliferative response of RITA alone and in combination with 5FU or oxaliplatin in human CRC cells. A panel of long-term established CRC cell lines (n = 9) including p53 wild-type, p53 mutant, and p53 null and primary patient-derived, low-passage cell lines (n = 5) with different p53 protein status were used for this study. A substantial number of CRC cells with pronounced sensitivity to RITA (IC₅₀< 3.0 μmol/l) were identified within established (4/9) and primary patient-derived (2/5) CRC cell lines harboring wild-type or mutant p53 protein. Sensitivity to RITA appeared independent of p53 status and was associated with an increase in antiproliferative response to 5FU and oxaliplatin, a transcriptional increase of p53 targets p21 and NOXA, and a decrease in MYC mRNA. The effect of RITA as an inducer of DNA damage was shown by a strong elevation of phosphorylated histone variant H2A.X, which was restricted to RITA-sensitive cells. Our data underline the primary effect of RITA, inducing DNA damage, and demonstrate the differential antiproliferative effect of RITA to CRC cells independent of p53 protein status. We found a substantial number of RITA-sensitive CRC cells within both panels of established CRC cell lines and primary patient-derived CRC cell lines (6/14) that provide a rationale for combining RITA with 5FU or oxaliplatin to enhance the antiproliferative response to both chemotherapeutic agents.

Comparison of patient-derived high and low phosphatidylserine-exposing colorectal carcinoma cells in their interaction with anti-cancer peptides

Current cancer treatment is frequently compromised by severe adverse effects on healthy cells and tissues as well as by the increasing burden of (multi-)drug resistances. Some representatives of small, amphipathic peptides known as host defense peptides possess the potential to overcome these limitations and to evolve as future anti-cancer therapeutics. Peptide NK-2, derived from porcine NK-lysin, was originally discovered due to its broad-spectrum antimicrobial activities. Today, also potent anti-cancer activity is proven and accompanied by low toxicity towards normal human cells. The molecular basis underlying this target selectivity remains rather elusive. Nevertheless, it is presumptive that preferential peptide interactions with surface factors non-abundant on healthy human cells play a key role. Here, we investigated the cytotoxicity of peptide NK-2 and structurally improved anti-cancer variants thereof against two patient-derived colorectal cancer cell lines, exposing high and low levels of phosphatidylserine on their cell surfaces, respectively. Concluding from a range of in vitro tests involving cellular as well as lipid vesicle-based methods, it is proposed that the magnitude of the accessible membrane surface charge is not a primarily decisive factor for selective peptide interactions. Instead, it is suggested that the level of membrane surface-exposed phosphatidylserine is of crucial importance for the activity of peptide NK-2 and enhanced variants thereof in terms of their cancer cell selectivity, the overall efficacy, as well as the underlying mode of action and kinetics. Copyright © 2017 European Peptide Society and John Wiley & Sons, Ltd.

Efficacy of NEDD8 Pathway Inhibition in Preclinical Models of Poorly Differentiated, Clinically Aggressive Colorectal Cancer

Background

The NEDD8 conjugation pathway modulates the ubiquitination and activity of a wide range of intracellular proteins, and its blockade by pevonedistat is emerging as a promising therapeutic approach in various cancer settings. However, systematic characterization of pevonedistat efficacy in specific tumor types and definition of response predictors are still missing.

Methods

We investigated in vitro sensitivity to pevonedistat in 122 colorectal cancer (CRC) cell lines by an ATP-based proliferation assay and evaluated apoptosis and DNA content by flow cytometry. Associations between pevonedistat sensitivity and CRC molecular features were assessed by Student's t test. A 184-gene transcriptional predictor was generated in cell lines and applied to 87 metastatic CRC samples for which patient-derived xenografts (PDXs) were available. In vivo reponse to pevonedistat was assessed in PDX models (≥5 mice per group). All statistical tests were two-sided.

Results

Sixteen (13.1%) cell lines displayed a marked response to pevonedistat, featuring DNA re-replication, proliferative block, and increased apoptosis. Pevonedistat sensitivity did not statistically significantly correlate with microsatellite instability or mutations in KRAS or BRAF and was functionally associated with low EGFR pathway activity. While ineffective on predicted resistant PDXs, in vivo administration of pevonedistat statistically significantly impaired growth of five out of six predicted sensitive models (P < .01). In samples from CRC patients, transcriptional prediction of pevonedistat sensitivity was associated with poor prognosis after surgery (hazard ratio [HR] = 2.49, 95% confidence interval [CI] = 1.34 to 4.62, P = .003) and early progression under cetuximab treatment (HR = 3.59, 95% CI = 1.60 to 8.04, P < .001). Histological and immunohistochemical analyses revealed that the pevonedistat sensitivity signature captures transcriptional traits of poor differentiation and high-grade mucinous adenocarcinoma.

Conclusions

These results highlight NEDD8-pathway inhibition by pevonedistat as a potentially effective treatment for poorly differentiated, clinically aggressive CRC.

Generation, Characterization and Application of Antibodies Directed against HERV-H Gag Protein in Colorectal Samples

Introduction

A substantial part of the human genome originates from transposable elements, remnants of ancient retroviral infections. Roughly 8% of the human genome consists of about 400,000 LTR elements including human endogenous retrovirus (HERV) sequences. Mainly, the interplay between epigenetic and post-transcriptional mechanisms is thought to silence HERV expression in most physiological contexts. Interestingly, aberrant reactivation of several HERV-H loci appears specific to colorectal carcinoma (CRC).

Results

The expression of HERV-H Gag proteins (Gag-H) was assessed using novel monoclonal mouse anti Gag-H antibodies. In a flow cytometry screen four antibody clones were tested on a panel of primary CRC cell lines and the most well performing ones were subsequently validated in western blot analysis. Finally, Gag-H protein expression was analyzed by immune histology on cell line cytospins and on clinical samples. There, we found a heterogeneous staining pattern with no background staining of endothelial, stromal and infiltrating immune cells but diffuse staining of the cytoplasm for positive tumor and normal crypt cells of the colonic epithelium.

Conclusion

Taken together, the Gag-H antibody clone(s) present a valuable tool for staining of cells with colonic origin and thus form the basis for future more detailed investigations. The observed Gag-H protein staining in colonic epithelium crypt cells demands profound analyses of a potential role for Gag-H in the normal physiology of the human gut.

Establishment and characterization of HROC69 - a Crohn´s related colonic carcinoma cell line and its matched patient-derived xenograft

Colitis-associated colorectal cancer (CAC) seems to be a rather unique entity and differs in its genetic alterations, tumour formation capacities, and clinical features from sporadic colorectal carcinoma. Most descriptions about tumour biology of CAC refer to ulcerative colitis; data about Crohn´s colitis related carcinomas are scarce. The majority of patients with Crohn´s disease are under immunosuppression which generates a different environment for tumour growth. We first describe the clinical case of a fast growing CAC in a long-term immunosuppressed patient with Crohn´s disease and successful establishment and characterization of carcinoma cell lines along with their corresponding patient-derived xenograft. Subsequently, these tumor models were molecularly and functionally analysed. Beside numerous chromosomal alterations, mutations in TP53, APC, PTEN and SMAD3 were identified. The cell lines express numerous cancer testis antigens, surface molecules involved in immune evasion but low levels of HLA class I molecules. They show strong invasive but in comparison weak migratory activity. The present work is the first description of patient-derived in vitro and in vivo models for CAC from a Crohn´s disease patient. They might be valuable tools for analysis of genetic and epigenetic alterations, biomarker identification, functional testing, including response prediction, and the development of specific therapeutical strategies.

Functional Characterization and Drug Response of Freshly Established Patient-Derived Tumor Models with CpG Island Methylator Phenotype

Patient-individual tumor models constitute a powerful platform for basic and translational analyses both in vitro and in vivo. However, due to the labor-intensive and highly time-consuming process, only few well-characterized patient-derived cell lines and/or corresponding xenografts exist. In this study, we describe successful generation and functional analysis of novel tumor models from patients with sporadic primary colorectal carcinomas (CRC) showing CpG island methylator phenotype (CIMP). Initial DNA fingerprint analysis confirmed identity with the patient in all four cases. These freshly established cells showed characteristic features associated with the CIMP-phenotype (HROC40: APC^wt, TP53^mut, KRAS^mut; 3/8 marker methylated; HROC43: APC^mut, TP53^mut, KRAS^mut; 4/8 marker methylated; HROC60: APC^wt, TP53^mut, KRAS^wt; 4/8 marker methylated; HROC183: APC^mut, TP53^mut, KRAS^mut; 6/8 marker methylated). Cell lines were of epithelial origin (EpCAM⁺) with distinct morphology and growth kinetics. Response to chemotherapeutics was quite individual between cells, with stage I-derived cell line HROC60 being most susceptible towards standard clinically approved chemotherapeutics (e.g. 5-FU, Irinotecan). Of note, most cell lines were sensitive towards “non-classical” CRC standard drugs (sensitivity: Gemcitabin > Rapamycin > Nilotinib). This comprehensive analysis of tumor biology, genetic alterations and assessment of chemosensitivity towards a broad range of (chemo-) therapeutics helps bringing forward the concept of personalized tumor therapy.