The prognostic effect of tumor-associated macrophages in stage I-III colorectal cancer depends on T cell infiltration

BACKGROUND

Tumor-associated macrophages (TAMs) are associated with unfavorable patient prognosis in many cancer types. However, TAMs are a heterogeneous cell population and subsets have been shown to activate tumor-infiltrating T cells and confer a good patient prognosis. Data on the prognostic value of TAMs in colorectal cancer are conflicting. We investigated the prognostic effect of TAMs in relation to tumor-infiltrating T cells in colorectal cancers.

METHODS

The TAM markers CD68 and CD163 were analyzed by multiplex fluorescence immunohistochemistry and digital image analysis on tissue microarrays of 1720 primary colorectal cancers. TAM density in the tumor stroma was scored in relation to T cell density (stromal CD3+ and epithelial CD8+ cells) and analyzed in Cox proportional hazards models of 5-year relapse-free survival. Multivariable survival models included clinicopathological factors, MSI status and BRAFV600E mutation status.

RESULTS

High TAM density was associated with a favorable 5-year relapse-free survival in a multivariable model of patients with stage I-III tumors (p = 0.004, hazard ratio 0.94, 95% confidence interval 0.90-0.98). However, the prognostic effect was dependent on tumoral T-cell density. High TAM density was associated with a good prognosis in patients who also had high T-cell levels in their tumors, while high TAM density was associated with poorer prognosis in patients with low T-cell levels (pinteraction = 0.0006). This prognostic heterogeneity was found for microsatellite stable tumors separately.

CONCLUSIONS

This study supported a phenotypic heterogeneity of TAMs in colorectal cancer, and showed that combined tumor immunophenotyping of multiple immune cell types improved the prediction of patient prognosis.

E-cadherin is a robust prognostic biomarker in colorectal cancer and low expression is associated with sensitivity to inhibitors of topoisomerase, aurora, and HSP90 in preclinical models

Cell–cell and cell–matrix adhesion proteins that have been implicated in colorectal epithelial integrity and epithelial‐to‐mesenchymal transition could be robust prognostic and potential predictive biomarkers for standard and novel therapies. We analyzed in situ protein expression of E‐cadherin (ECAD), integrin β4 (ITGB4), zonula occludens 1 (ZO‐1), and cytokeratins in a single‐hospital series of Norwegian patients with colorectal cancer (CRC) stages I–IV (n = 922) using multiplex fluorescence‐based immunohistochemistry (mfIHC) on tissue microarrays. Pharmacoproteomic associations were explored in 35 CRC cell lines annotated with drug sensitivity data on > 400 approved and investigational drugs. ECAD, ITGB4, and ZO‐1 were positively associated with survival, while cytokeratins were negatively associated with survival. Only ECAD showed independent prognostic value in multivariable Cox models. Clinical and molecular associations for ECAD were technically validated on a different mfIHC platform, and the prognostic value was validated in another Norwegian series (n = 798). In preclinical models, low and high ECAD expression differentially associated with sensitivity to topoisomerase, aurora, and HSP90 inhibitors, and EGFR inhibitors. E‐cadherin protein expression is a robust prognostic biomarker with potential clinical utility in CRC.

The expressed mutational landscape of microsatellite stable colorectal cancers

Background

Colorectal cancer is the 2nd leading cause of cancer-related deaths with few patients benefiting from biomarker-guided therapy. Mutation expression is essential for accurate interpretation of mutations as biomarkers, but surprisingly, little has been done to analyze somatic cancer mutations on the expression level. We report a large-scale analysis of allele-specific mutation expression.

Methods

Whole-exome and total RNA sequencing was performed on 137 samples from 121 microsatellite stable colorectal cancers, including multiregional samples of primary and metastatic tumors from 4 patients. Data were integrated with allele-specific resolution. Results were validated in an independent set of 241 colon cancers. Therapeutic associations were explored by pharmacogenomic profiling of 15 cell lines or patient-derived organoids.

Results

The median proportion of expressed mutations per tumor was 34%. Cancer-critical mutations had the highest expression frequency (gene-wise mean of 58%), independent of frequent allelic imbalance. Systematic deviation from the general pattern of expression levels according to allelic frequencies was detected, including preferential expression of mutated alleles dependent on the mutation type and target gene. Translational relevance was suggested by correlations of KRAS/NRAS or TP53 mutation expression levels with downstream oncogenic signatures (p < 0.03), overall survival among patients with stage II and III cancer (KRAS/NRAS: hazard ratio 6.1, p = 0.0070), and targeted drug sensitivity. The latter was demonstrated for EGFR and MDM2 inhibition in pre-clinical models.

Conclusions

Only a subset of mutations in microsatellite stable colorectal cancers were expressed, and the “expressed mutation dose” may provide an opportunity for more fine-tuned biomarker interpretations.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13073-021-00955-2.

Prediction of relapse-free survival according to adjuvant chemotherapy and regulator of chromosome condensation 2 (RCC2) expression in colorectal cancer

BACKGROUND

There is a need for improved selection of patients for adjuvant chemotherapy after resection of non-metastatic colorectal cancer (CRC). Regulator of chromosome condensation 2 (RCC2) is a potential prognostic biomarker. We report on the establishment of a robust protocol for RCC2 expression analysis and prognostic tumour biomarker evaluation in patients who did and did not receive adjuvant chemotherapy.

MATERIALS AND METHODS

RCC2 was analysed in 2916 primary CRCs from the QUASAR2 randomised trial and two single-hospital Norwegian series. A new protocol using fluorescent antibody staining and digital image analysis was optimised. Biomarker value for 5-year relapse-free survival was analysed in relation to tumour stage, adjuvant chemotherapy and the molecular markers microsatellite instability, KRAS/BRAFV600E/TP53 mutations and CDX2 expression.

RESULTS

Low RCC2 expression was scored in 41% of 2696 evaluable samples. Among patients with stage I-III CRC who had not received adjuvant chemotherapy, low RCC2 expression was an independent marker of inferior 5-year relapse-free survival in multivariable Cox models including clinicopathological factors and molecular markers (HR 1.45, 95% CI 1.09 to 1.94, p=0.012, N=521). RCC2 was not prognostic in patients who had received adjuvant chemotherapy, neither in QUASAR2 nor the pooled Norwegian series. The interaction between RCC2 and adjuvant chemotherapy for prediction of patient outcome was significant in stage III, and strongest among patients with microsatellite stable tumours (pinteraction=0.028).

CONCLUSIONS

Low expression of RCC2 is a biomarker for poor prognosis in patients with stage I-III CRC and seems to be a predictive biomarker for effect of adjuvant chemotherapy.

Abstract 1433: Role of the E3 ubiquitin ligase NEDD4 in the regulation of PTEN and MDM2 in colorectal cancer

Introduction: NEDD4 (neural precursor cell-expressed developmentally down-regulated 4), a member of the HECT (homologous to E6AP C-terminus) family of E3 ubiquitin ligases, has been shown to be an important regulator of multiple proteins involved in cancer development, including the tumor suppressor PTEN and the proto-oncogene MDM2. Furthermore, NEDD4 has been shown to be overexpressed and act as an oncogene in multiple cancer types. We have previously shown that NEDD4 is overexpressed in colorectal cancer (CRC) and that it can promote growth of colon cancer cells independently of PTEN and PI3K/AKT signaling. In the present study, we investigated the role of NEDD4 in regulating the PTEN/PI3K pathway and the MDM2/p53 axis in CRC.

Materials and Methods: The CRISPR/Cas9 system was applied to generate a Caco2 NEDD4 knockout cell line, and NEDD4 knockdown was performed in LS174T and SW480 cells. Gene expression profiles of 412 primary CRCs, 51 normal mucosa samples, 38 CRC cell lines, as well as the Caco2 parental and NEDD4 knockout cell lines, were generated using exon-resolution Affymetrix Human Exon Arrays or Human Transcriptome Arrays. The NEDD4 expression level was correlated with the mutation status of KRAS, PTEN, TP53, PIK3CA, BRAF and NRAS. Western blotting was used to detect and quantify NEDD4, PTEN and MDM2 protein levels.

Results and Discussions: Gene expression analysis of the patient material confirmed our previous study that NEDD4 is significantly upregulated in CRC as compared to normal colonic mucosa. There was no correlation between NEDD4 expression and mutations in KRAS, BRAF, NRAS, PTEN, PIK3CA and TP53. CRISPR/Cas9-mediated NEDD4 knockout in Caco2 cells resulted in a reduction (P &lt;0.01) in both the PTEN and MDM2 protein levels as compared to control cells. Gene set analysis showed that PI3K/AKT/MTOR signaling was upregulated in the NEDD4 knockout cells as compared to control cells. siRNA-mediated depletion of NEDD4 in LS174T cells was associated with reduced levels of MDM2, but did not affect the PTEN protein level. In SW480 cells, depletion of NEDD4 affected neither the MDM2 nor the PTEN protein level. By analyzing the expression of NEDD4, PTEN and MDM2 in 38 CRC cell lines by Western blotting, a positive correlation (P&lt;0.01) was observed between NEDD4 and PTEN protein, while there was no significant correlation between NEDD4 and MDM2.

Conclusion: The data show that NEDD4 is significantly upregulated in CRC, and that NEDD4 expression correlates with PTEN expression. The data further suggest that NEDD4 has the ability to regulate the PTEN and MDM2 protein levels in colon cancer cells in a cell line-specific manner.

Citation Format: Lars M. Knudsen, Anita Sveen, Christer A. Andreassen, Christian H. Bergsland, Ina A. Eilertsen, Nikoline L. Rasmussen, Max Z. Totland, Peter W. Eide, Jarle Bruun, Ragnhild A. Lothe, Edward Leithe. Role of the E3 ubiquitin ligase NEDD4 in the regulation of PTEN and MDM2 in colorectal cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1433.

Molecular correlates of sensitivity to PARP inhibition beyond homologous recombination deficiency in pre-clinical models of colorectal cancer point to wild-type TP53 activity

BACKGROUND

PARP inhibitors are active in various tumour types beyond BRCA-mutant cancers, but their activity and molecular correlates in colorectal cancer (CRC) are not well studied.

METHODS

Mutations and genome-wide mutational patterns associated with homologous recombination deficiency (HRD) were investigated in 255 primary CRCs with whole-exome sequencing and/or DNA copy number data. Efficacy of five PARP inhibitors and their molecular correlates were evaluated in 93 CRC cell lines partly annotated with mutational-, DNA copy number-, and/or gene expression profiles. Post-treatment gene expression profiling and specific protein expression analyses were performed in two pairs of PARP inhibitor sensitive and resistant cell lines.

FINDINGS

A subset of microsatellite stable (MSS) CRCs had truncating mutations in homologous recombination-related genes, but these were not associated with genomic signatures of HRD. Eight CRC cell lines (9%) were sensitive to PARP inhibition, but sensitivity was not predicted by HRD-related genomic and transcriptomic signatures. In contrast, drug sensitivity in MSS cell lines was strongly associated with TP53 wild-type status (odds ratio 15.7, p = 0.023) and TP53-related expression signatures. Increased downstream TP53 activity was among the primary response mechanisms, and TP53 inhibition antagonized the effect of PARP inhibitors. Wild-type TP53-mediated suppression of RAD51 was identified as a possible mechanism of action for sensitivity to PARP inhibition.

INTERPRETATION

PARP inhibitors are active in a subset of CRC cell lines and preserved TP53 function may increase the likelihood of response.

Abstract A19: Modeling intrapatient pharmacotranscriptomic heterogeneity with organoids derived from colorectal cancer liver metastases

Patients with metastatic colorectal cancer (CRC) have few targeted treatment options compared with other major malignancies, and both over- and undertreatment with cytostatic drugs remain a challenge. Recent studies show that patient-derived organoids (PDOs) can predict clinical responses to systemic therapies in a personalized manner, but tumor heterogeneity may limit the clinical benefit of anticancer therapies, as well as the accuracy of preclinical predictions. PDO lineage establishment from multiple distinct lesions per patient presents a novel opportunity for preclinical investigation of intrapatient pharmacotranscriptomic heterogeneity. From September 2017 until November 2019, we have established a living biobank of 107 PDOs from 53 patients who underwent resection of CRC liver metastases at Oslo University Hospital, Norway, 31 of whom had multiple (2-5) metastases. All PDOs were screened for sensitivity to 40 anticancer agents, including clinically relevant targeted drugs and conventional chemotherapies. Molecular profiling by gene expression and mutation analyses is ongoing and currently completed for 27 PDOs. Recapitulation of known pharmacogenomic/transcriptomic associations was confirmed in PDOs for EGFR inhibition and RAS/BRAFV600E mutation status, as well as TP53-MDM2 inhibition and TP53 mutation status and TP53 transcriptional activity. Antimetabolites such as gemcitabine and methotrexate, or small-molecule inhibitors in late-stage clinical development targeting Aurora A, PLK1, and HSP90, showed strong differential activities, enabling identification of sensitive subgroups. Strong sensitivity to HSP90 inhibition was associated with low protein expression of Heat Shock Transcription Factor 1, which had a homogenous intrapatient intermetastatic expression pattern. Principal component analyses revealed a clear patient-wise separation of PDOs based on both their pharmacologic and transcriptomic profiles separately, indicating only modest intrapatient heterogeneity among distinct metastatic lesions. Accurate prediction of clinical responses to 5-FU and oxaliplatin was shown in PDOs from one patient treated for recurrent liver metastases. Additionally, PDOs from recurrent liver metastases showed an increased sensitivity to off-label drugs compared to PDOs from the first liver resection, supporting therapy repurposing in later lines of treatment. In summary, patient-derived models of CRC liver metastases reveal modest intrapatient pharmacotranscriptomic heterogeneity—an encouraging result for further efforts to develop personalized drug repurposing strategies for this poor-prognosis patient group.

Citation Format: Kushtrim Kryeziu, Jarle Bruun, Peter W. Eide, Seyed H. Moosavi, Ina A. Eilertsen, Jonas Langerud, Bård Røsok, Tuva H. Brunsell, Marianne G. Guren, Andreas Abildgaard, Arild Nesbakken, Bjørn Atle Bjørnbeth, Anita Sveen, Ragnhild A. Lothe. Modeling intrapatient pharmacotranscriptomic heterogeneity with organoids derived from colorectal cancer liver metastases [abstract]. In: Proceedings of the AACR Special Conference on the Evolving Landscape of Cancer Modeling; 2020 Mar 2-5; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2020;80(11 Suppl):Abstract nr A19.

Patient-Derived Organoids from Multiple Colorectal Cancer Liver Metastases Reveal Moderate Intra-patient Pharmacotranscriptomic Heterogeneity

PURPOSE

Molecular tumor heterogeneity may have important implications for the efficacy of targeted therapies in metastatic cancers. Inter-metastatic heterogeneity of sensitivity to anticancer agents has not been well explored in colorectal cancer.

EXPERIMENTAL DESIGN

We established a platform for ex vivo pharmacogenomic profiling of patient-derived organoids (PDO) from resected colorectal cancer liver metastases. Drug sensitivity testing (n = 40 clinically relevant agents) and gene expression profiling were performed on 39 metastases from 22 patients.

RESULTS

Three drug-response clusters were identified among the colorectal cancer metastases, based primarily on sensitivities to EGFR and/or MDM2 inhibition, and corresponding with RAS mutations and TP53 activity. Potentially effective therapies, including off-label use of drugs approved for other cancer types, could be nominated for eighteen patients (82%). Antimetabolites and targeted agents lacking a decisive genomic marker had stronger differential activity than most approved chemotherapies. We found limited intra-patient drug sensitivity heterogeneity between PDOs from multiple (2-5) liver metastases from each of ten patients. This was recapitulated at the gene expression level, with a highly proportional degree of transcriptomic and pharmacological variation. One PDO with a multi-drug resistance profile, including resistance to EGFR inhibition in a RAS-mutant background, showed sensitivity to MEK plus mTOR/AKT inhibition, corresponding with low-level PTEN expression.

CONCLUSIONS

Intra-patient inter-metastatic pharmacological heterogeneity was not pronounced and ex vivo drug screening may identify novel treatment options for metastatic colorectal cancer. Variation in drug sensitivities was reflected at the transcriptomic level, suggesting potential to develop gene expression-based predictive signatures to guide experimental therapies.

Digital image analysis of multiplex fluorescence IHC in colorectal cancer recognizes the prognostic value of CDX2 and its negative correlation with SOX2

Flourescence-based multiplex immunohistochemistry (mIHC) combined with multispectral imaging and digital image analysis (DIA) is a quantitative high-resolution method for determination of protein expression in tissue. We applied this method for five biomarkers (CDX2, SOX2, SOX9, E-cadherin, and β-catenin) using tissue microarrays of a Norwegian unselected series of primary colorectal cancer. The data were compared with previously obtained chromogenic IHC data of the same tissue cores, visually assessed by the Allred method. We found comparable results between the methods, although confirmed that DIA offered improved resolution to differentiate cases with high and low protein expression. However, we experienced inherent challenges with digital image analysis of membrane staining, which was better assessed visually. DIA and mIHC enabled quantitative analysis of biomarker coexpression on the same tissue section at the single-cell level, revealing a strong negative correlation between the differentiation markers CDX2 and SOX2. Both methods confirmed known prognostic associations for CDX2, but DIA improved data visualization and detection of clinicopathological and biological associations. In summary, mIHC combined with DIA is an efficient and reliable method to evaluate protein expression in tissue, here shown to recapitulate and improve detection of known clinicopathological and survival associations for the emerging biomarker CDX2, and is therefore a candidate approach to standardize CDX2 detection in pathology laboratories.

Correction: Tumour-infiltrating CD8+ lymphocytes and colorectal cancer recurrence by tumour and nodal stage

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Tumour-infiltrating CD8+ lymphocytes and colorectal cancer recurrence by tumour and nodal stage

BACKGROUND

Intratumoural T-cell infiltrate intensity cortes wrelaith clinical outcome in stage II/III colorectal cancer (CRC). We aimed to determine whether this association varies across this heterogeneous group.

METHODS

We performed a pooled analysis of 1804 CRCs from the QUASAR2 and VICTOR trials. Intratumoural CD8+ and CD3+ densities were quantified by immunohistochemistry in tissue microarray (TMA) cores, and their association with clinical outcome analysed by Cox regression. We validated our results using publicly available gene expression data in a pooled analysis of 1375 CRCs from seven independent series.

RESULTS

In QUASAR2, intratumoural CD8+ was a stronger predictor of CRC recurrence than CD3+ and showed similar discriminative ability to both markers in combination. Pooled multivariable analysis of both trials showed increasing CD8+ density was associated with reduced recurrence risk independent of confounders including DNA mismatch repair deficiency, POLE mutation and chromosomal instability (multivariable hazard ratio [HR] for each two-fold increase = 0.92, 95%CI = 0.87-0.97, P = 3.6 × 10-3). This association was not uniform across risk strata defined by tumour and nodal stage: absent in low-risk (pT3,N0) cases (HR = 1.03, 95%CI = 0.87-1.21, P = 0.75), modest in intermediate-risk (pT4,N0 or pT1-3,N1-2) cases (HR = 0.92, 95%CI = 0.86-1.0, P = 0.046) and strong in high-risk (pT4,N1-2) cases (HR = 0.87, 95%CI = 0.79-0.97, P = 9.4 × 10-3); PINTERACTION = 0.090. Analysis of tumour CD8A expression in the independent validation cohort revealed similar variation in prognostic value across risk strata (PINTERACTION = 0.048).

CONCLUSIONS

The prognostic value of intratumoural CD8+ cell infiltration in stage II/III CRC varies across tumour and nodal risk strata.

Exploratory analyses of consensus molecular subtype-dependent associations of TP53 mutations with immunomodulation and prognosis in colorectal cancer

Background

Accumulating evidence suggests immunomodulatory and context-dependent effects of TP53 mutations in cancer. We performed an exploratory analysis of the transcriptional, immunobiological and prognostic associations of TP53 mutations within the gene expression-based consensus molecular subtypes (CMSs) of colorectal cancer (CRC).

Materials and methods

In a single-hospital series of 401 stage I–IV primary CRCs, we sequenced the whole coding region of TP53 and analysed CMS-dependent transcriptional consequences of the mutations by gene expression profiling. Immunomodulatory associations were validated by multiplex, fluorescence-based immunohistochemistry of immune cell markers. Prognostic associations of TP53 mutations were analysed in an aggregated series of 635 patients classified according to CMS, including publicly available data from a French multicentre cohort (GSE39582).

Results

TP53 mutations were found in 60% of the CRCs. However, gene set enrichment analyses indicated that their transcriptional consequences varied among the CMSs and were most pronounced in CMS1-immune and CMS4-mesenchymal. Subtype specificity was primarily seen as an upregulation of gene sets reflecting cell cycle progression in CMS4 and a downregulation of T cell activity in CMS1. The subtype-dependent immunomodulatory associations were reinforced by significant depletion of several immune cell populations in mutated tumours compared with wild-type (wt) tumours exclusively in CMS1, including cytotoxic lymphocytes (adjusted p value in CMS1=0.002 and CMS2−4>0.9, Microenvironment Cell Populations (MCP)-counter algorithm). This was validated by immunohistochemistry-based quantification of tumour infiltrating CD8+ cells. Within CMS1, the immunomodulatory association of TP53 mutations was strongest among microsatellite stable (MSS) tumours, and this translated into a propensity for metastatic disease and poor prognostic value of the mutations specifically in the CMS1/MSS subtype (both series overall survival: TP53 mutation vs wt: HR 5.52, p=0.028).

Conclusions

Integration of TP53 mutation status with the CMS framework in primary CRC suggested subtype-dependent immunobiological associations with prognostic and potentially immunotherapeutic implications, warranting independent validation.

Combination therapies with HSP90 inhibitors against colorectal cancer

Oncogene stability and homeostasis mediated by the HSP90 chaperone is a crucial protection trait of cancer cells. Therefore, HSP90 represents an attractive therapeutic target for many cancers, including colorectal cancer. Although monotherapy has limited clinical efficacy, preclinical and early-phase clinical studies indicate improved antitumor activity when HSP90 inhibitors are combined with chemotherapies or targeted agents. This may be further improved with a biomarker-guided approach based on oncogenic HSP90 clients, or stratification based on the consensus molecular subtypes of colorectal cancer, suggesting a synergistic activity with 5-fluorouracil in preclinical models of the chemorefractory mesenchymal subtype. Furthermore, HSP90 inhibition may activate mechanisms to turn non-immunogenic tumors hot and improve their recognition by the immune system, suggesting synergy with immune checkpoint blockade.

Abstract B30: Digital multiplex immunofluorescence analysis identifies immune profiles in the tumor stroma associated with clinical outcome

Background: The recent successes of immunotherapy in non-small cell lung cancer (NSCLC) raise the interest to the deeper understanding of the diversity of the immune microenvironment. Meticulous characterization of the immune cell infiltrates is crucial for patients’ prognosis and the prediction therapeutic effects. The aim of this study was to analyze expression profiles of the immune cells and their linkage to clinical parameters in NSCLC patients.

Methods: A tissue microarray of the NSCLC cohort comprised of 55 cases was used in the study. The staining was performed with the antibodies against CD8, CD20, CD4, FoxP3, CD45RO and pan-cytokeratin together with immuno-fluorescent markers (Opal, Perkin Elmer) and digital images acquired by a multispectral imaging system (Vectra 3, PerkinElmer). Marker expression pattern was evaluated on a cell level in total sample area, or in stroma and tumor area separately. Conventional immunohistochemical techniques and RNAseq data were used to validate the method.

Results: Marker expression intensities were used to identify 5 non-epithelial cell classes, which express CD8, CD20, CD4, FoxP3, CD45RO. Relative abundance of marker-positive cells in individual cases were subjected to hierarchical clustering analysis, for the discovery of distinct immune cell infiltration patterns. The resulted clusters were exploratively analyzed with regard to survival associations. Patients with specific immune profile with high infiltration of FoxP3+ cells, moderate infiltration of CD4+ and CD8+ cells and low quantity of CD20+ and CD45RO+ cells in the stroma were associated with longer survival (median 87 vs. 54 month, log-rank p=0.050).

Conclusion: Multi-marker analysis on single-cell levels with the fluorescence multiplexed IHC technique provides a valuable basic immune profile of cancer patients. Clustering analysis of the expression of immune markers identified a group of patients with improved survival in NSCLC independent of histology.

Note: This abstract was not presented at the conference.

Citation Format: Artur Mezheyeuski, Christian Bergsland, Max Backman, Tobias Sjöblom, Ragnhild A. Lothe, Jarle Bruun, Patrick Micke. Digital multiplex immunofluorescence analysis identifies immune profiles in the tumor stroma associated with clinical outcome [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2017 Oct 1-4; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2018;6(9 Suppl):Abstract nr B30.

Prognostic, predictive, and pharmacogenomic assessments of CDX2 refine stratification of colorectal cancer

We aimed to refine the value of CDX2 as an independent prognostic and predictive biomarker in colorectal cancer (CRC) according to disease stage and chemotherapy sensitivity in preclinical models. CDX2 expression was evaluated in 1045 stage I–IV primary CRCs by gene expression (n = 403) or immunohistochemistry (n = 642) and in relation to 5‐year relapse‐free survival (RFS), overall survival (OS), and chemotherapy. Pharmacogenomic associations between CDX2 expression and 69 chemotherapeutics were assessed by drug screening of 35 CRC cell lines. CDX2 expression was lost in 11.6% of cases and showed independent poor prognostic value in multivariable models. For individual stages, CDX2 was prognostic only in stage IV, independent of chemotherapy. Among stage I–III patients not treated in an adjuvant setting, CDX2 loss was associated with a particularly poor survival in the BRAF‐mutated subgroup, but prognostic value was independent of microsatellite instability status and the consensus molecular subtypes. In stage III, the 5‐year RFS rate was higher among patients with loss of CDX2 who received adjuvant chemotherapy than among patients who did not. The CDX2‐negative cell lines were significantly more sensitive to chemotherapeutics than CDX2‐positive cells, and the multidrug resistance genes MDR1 and CFTR were significantly downregulated both in CDX2‐negative cells and in patient tumors. Loss of CDX2 in CRC is an adverse prognostic biomarker only in stage IV disease and appears to be associated with benefit from adjuvant chemotherapy in stage III. Early‐stage patients not qualifying for chemotherapy might be reconsidered for such treatment if their tumor has loss of CDX2 and mutated BRAF.

Abstract 565: CDX2 targets, GPA33 and LI-cadherin, are novel biomarkers with prognostic value in gastric cancer

Gastric cancer is one of the most common types of cancer and the third cause of cancer-related death worldwide. The aggressiveness of the disease is related to, among other factors, tumour differentiation. CDX2 is a known intestinal differentiation marker with prognostic value in gastric cancer and two of its targets are expressed at the cell surface: GPA33 (glycoprotein A33) and LI-cadherin (liver intestine cadherin). Whether these membrane proteins are good biomarkers in gastric cancer and could refine the significance of CDX2 expression remains unknown. In order to answer these questions, we evaluated the expression of CDX2, GPA33 and LI-cadherin using immunohistochemistry in 350 gastric cancer samples arranged in TMAs (tissue microarrays) and evaluated the co-localization of the biomarkers using fluorescent multiplex immunohistochemistry.

CDX2 was expressed in 36% of the cases, while GPA33 and LI-cadherin were positive in 55% and 66%, respectively. All markers were significantly correlated with each other and are more often expressed in early stage (I and II) cancers (p &lt; 0.05). Overall survival analysis showed that both GPA33 and LI-cadherin predict better outcome. When stratifying the series in early (I and II) and late (III and IV) stages, both proteins significantly associate with better outcome for late stages of disease progression. Overall, these data indicate that the presence of an intestinal differentiation program in gastric cancer is a marker of good prognosis.

The concordance rate between CDX2 and GPA33 and CDX2 and LI-cadherin expression was 68% and 64%, respectively. Since CDX2 displays a heterogeneous pattern of expression and TMA sampling can, by chance, select a negative area in a positive tumour, we also compared CDX2 expression between whole-tissue sections and TMAs. In our series we obtained 68 discrepant cases (positive for CDX2 in whole-tissue sections and negative in the TMAs). For the majority of these cases (50, corresponding to 74%) the combined expression of CDX2 targets, GPA33 and LI-cadherin, can rescue the underrepresentation of CDX2 expression in the TMAs and identifies CDX2-dependent intestinal differentiation.

We conclude that CDX2, GPA33 and LI-cadherin are significantly associated with each other and are commonly expressed in early stages of gastric cancer. The expression of GPA33 and LI-cadherin is associated with better overall survival, particularly in late-stage disease patients. Finally, GPA33 and LI-cadherin are good cell surface surrogate markers for CDX2 expression, not only because of the good concordance of expression, but also because the combined expression of GPA33 and LI-cadherin rescues false negative CDX2 cases in TMAs versus whole-tissue samples.

Citation Format: Nair Lopes, Christian Bergsland, Merete Bjornslett, Jarle Bruun, Ragnhild Lothe, Raquel Almeida, Leonor David. CDX2 targets, GPA33 and LI-cadherin, are novel biomarkers with prognostic value in gastric cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 565.

Multispectral imaging for quantitative and compartment-specific immune infiltrates reveals distinct immune profiles that classify lung cancer patients

Semiquantitative assessment of immune markers by immunohistochemistry (IHC) has significant limitations for describing the diversity of the immune response in cancer. Therefore, we evaluated a fluorescence-based multiplexed immunohistochemical method in combination with a multispectral imaging system to quantify immune infiltrates in situ in the environment of non-small-cell lung cancer (NSCLC). A tissue microarray including 57 NSCLC cases was stained with antibodies against CD8, CD20, CD4, FOXP3, CD45RO, and pan-cytokeratin, and immune cells were quantified in epithelial and stromal compartments. The results were compared with those of conventional IHC, and related to corresponding RNA-sequencing (RNAseq) expression values. We found a strong correlation between the visual and digital quantification of lymphocytes for CD45RO (correlation coefficient: r = 0.52), FOXP3 (r = 0.87), CD4 (r = 0.79), CD20 (r = 0.81) and CD8 (r = 0.90) cells. The correlation with RNAseq data for digital quantification (0.35-0.65) was comparable to or better than that for visual quantification (0.38-0.58). Combination of the signals of the five immune markers enabled further subpopulations of lymphocytes to be identified and localized. The specific pattern of immune cell infiltration based either on the spatial distribution (distance between regulatory CD8⁺ T and cancer cells) or the relationships of lymphocyte subclasses with each other (e.g. cytotoxic/regulatory cell ratio) were associated with patient prognosis. In conclusion, the fluorescence multiplexed immunohistochemical method, based on only one tissue section, provided reliable quantification and localization of immune cells in cancer tissue. The application of this technique to clinical biopsies can provide a basic characterization of immune infiltrates to guide clinical decisions in the era of immunotherapy. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Colorectal Cancer Consensus Molecular Subtypes Translated to Preclinical Models Uncover Potentially Targetable Cancer Cell Dependencies

Purpose: Response to standard oncologic treatment is limited in colorectal cancer. The gene expression-based consensus molecular subtypes (CMS) provide a new paradigm for stratified treatment and drug repurposing; however, drug discovery is currently limited by the lack of translation of CMS to preclinical models.Experimental Design: We analyzed CMS in primary colorectal cancers, cell lines, and patient-derived xenografts (PDX). For classification of preclinical models, we developed an optimized classifier enriched for cancer cell-intrinsic gene expression signals, and performed high-throughput in vitro drug screening (n = 459 drugs) to analyze subtype-specific drug sensitivities.Results: The distinct molecular and clinicopathologic characteristics of each CMS group were validated in a single-hospital series of 409 primary colorectal cancers. The new, cancer cell-adapted classifier was found to perform well in primary tumors, and applied to a panel of 148 cell lines and 32 PDXs, these colorectal cancer models were shown to recapitulate the biology of the CMS groups. Drug screening of 33 cell lines demonstrated subtype-dependent response profiles, confirming strong response to EGFR and HER2 inhibitors in the CMS2 epithelial/canonical group, and revealing strong sensitivity to HSP90 inhibitors in cells with the CMS1 microsatellite instability/immune and CMS4 mesenchymal phenotypes. This association was validated in vitro in additional CMS-predicted cell lines. Combination treatment with 5-fluorouracil and luminespib showed potential to alleviate chemoresistance in a CMS4 PDX model, an effect not seen in a chemosensitive CMS2 PDX model.Conclusions: We provide translation of CMS classification to preclinical models and uncover a potential for targeted treatment repurposing in the chemoresistant CMS4 group. Clin Cancer Res; 24(4); 794-806. ©2017 AACR.

Drug sensitivity and resistance testing identifies PLK1 inhibitors and gemcitabine as potent drugs for malignant peripheral nerve sheath tumors

Patients with malignant peripheral nerve sheath tumor (MPNST), a rare soft tissue cancer associated with loss of the tumor suppressor neurofibromin (NF1), have poor prognosis and typically respond poorly to adjuvant therapy. We evaluated the effect of 299 clinical and investigational compounds on seven MPNST cell lines, two primary cultures of human Schwann cells, and five normal bone marrow aspirates, to identify potent drugs for MPNST treatment with few side effects. Top hits included Polo-like kinase 1 (PLK1) inhibitors (volasertib and BI2536) and the fluoronucleoside gemcitabine, which were validated in orthogonal assays measuring viability, cytotoxicity, and apoptosis. DNA copy number, gene expression, and protein expression were determined for the cell lines to assess pharmacogenomic relationships. MPNST cells were more sensitive to BI2536 and gemcitabine compared to a reference set of 94 cancer cell lines. PLK1, RRM1, and RRM2 mRNA levels were increased in MPNST compared to benign neurofibroma tissue, and the protein level of PLK1 was increased in the MPNST cell lines compared to normal Schwann cells, indicating an increased dependence on these drug targets in malignant cells. Furthermore, we observed an association between increased mRNA expression of PLK1, RRM1, and RRM2 in patient samples and worse disease outcome, suggesting a selective benefit from inhibition of these genes in the most aggressive tumors.

Multi-omics of 34 colorectal cancer cell lines - a resource for biomedical studies

Background

Colorectal cancer (CRC) cell lines are widely used pre-clinical model systems. Comprehensive insights into their molecular characteristics may improve model selection for biomedical studies.

Methods

We have performed DNA, RNA and protein profiling of 34 cell lines, including (i) targeted deep sequencing (n = 612 genes) to detect single nucleotide variants and insertions/deletions; (ii) high resolution DNA copy number profiling; (iii) gene expression profiling at exon resolution; (iv) small RNA expression profiling by deep sequencing; and (v) protein expression analysis (n = 297 proteins) by reverse phase protein microarrays.

Results

The cell lines were stratified according to the key molecular subtypes of CRC and data were integrated at two or more levels by computational analyses. We confirm that the frequencies and patterns of DNA aberrations are associated with genomic instability phenotypes and that the cell lines recapitulate the genomic profiles of primary carcinomas. Intrinsic expression subgroups are distinct from genomic subtypes, but consistent at the gene-, microRNA- and protein-level and dominated by two distinct clusters; colon-like cell lines characterized by expression of gastro-intestinal differentiation markers and undifferentiated cell lines showing upregulation of epithelial-mesenchymal transition and TGFβ signatures. This sample split was concordant with the gene expression-based consensus molecular subtypes of primary tumors. Approximately ¼ of the genes had consistent regulation at the DNA copy number and gene expression level, while expression of gene-protein pairs in general was strongly correlated. Consistent high-level DNA copy number amplification and outlier gene- and protein- expression was found for several oncogenes in individual cell lines, including MYC and ERBB2.

Conclusions

This study expands the view of CRC cell lines as accurate molecular models of primary carcinomas, and we present integrated multi-level molecular data of 34 widely used cell lines in easily accessible formats, providing a resource for preclinical studies in CRC.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-017-0691-y) contains supplementary material, which is available to authorized users.

Abstract 3122: Pharmacogenomic profiling to identify novel therapeutic strategies in colorectal cancer

Colorectal cancer (CRC) is amongst the most frequent cancers worldwide and the fourth most common cause of cancer mortality. Surgery is the standard treatment of care, while chemotherapy and/or radiotherapy are offered to subgroups of patients according to disease stage. Current guidelines do not have sufficient accuracy to identify chemotherapy responders, resulting in under- or overtreatment of many patients.To discover novel therapeutic strategies for CRC we performed a high-throughput drug screen containing 461 approved and preclinical drugs on a representative panel of 42 CRC cell lines. Integrative pharmacogenomic profiles were explored by matching data from gene expression, exome sequencing, copy number and reverse-phase protein arrays. These analyses identified defined molecular subgroups sensitive to targeted drugs like Inhibitors of EGFR, IGF-1R and downstream signaling mediators like B-Raf, MEK, PI3K/AKT, as well as inhibitors of aurora mitotic kinases, heat shock protein 90 and p53. Additionally, a correlation between microsatellite instability and sensitivity against topoisomerase-I inhibitors was found. Comparison of the most sensitive and the most resistant cell models against HSP90 inhibitors indicated that drug sensitivity does not depend on target expression but is likely attributed to the cell line-specific expression of client proteins. Real-time cell analyses measured with the xCELLigence system demonstrated a strong impact on cell proliferation but not on the migration of HSP90-sensitive cells treated with HSP90 inhibitors as compared to resistant cells. These integrative analyses have unraveled pharmacogenomic relationships that if validated in in vivo model systems, might be used to stratify patients for therapeutic intervention in biomarker guided clinical trials.

Citation Format: Jarle Bruun, Peter W. Eide, Kushtrim Kryeziu, Anita Sveen, Astrid Murumägi, Matthias Kolberg, Mariliina Arjama, Olli Kallioniemi, Ragnhild A. Lothe. Pharmacogenomic profiling to identify novel therapeutic strategies in colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3122. doi:10.1158/1538-7445.AM2017-3122

Novel drug discovery by pharmacogenomic profiling of 36 colorectal cancer cell lines

604

Background: Patients with advanced colorectal cancer (CRC) are commonly administered chemotherapy by 5-Fluorouracil in various combinations with leucovorin, oxaliplatin and irinotecan. Metastatic CRCs are additionally eligible for targeted anti-VEGF treatment and anti-EGFR therapy if the tumor is KRASwt. Unfortunately, the response rates are low and novel drugs are needed. Cell lines have successfully been employed to predict drug response and several studies have demonstrated that CRC cell lines recapitulate the genetic variation among primary CRCs. Methods: We performed a high-throughput drug screen (n= 461) of 36 CRC cell lines. A multiplexed assay assessed drug effects on cell viability and cytotoxicity from a five-fold concentration range. Sensitivities were measured by calculating a drug sensitivity score for each drug using a validated algorithm that estimates the relative inhibition by normalization against the top asymptote of the drug concentration curve. By integrating drug sensitivity data with in-house datasets on DNA copy number, gene expression and deep DNA sequencing, we aimed to validate genetically indicated drug sensitivities and identify novel drug sensitivities among subsets of CRCs. Results: Pharmacological relationships for molecular subgroups of CRC were revealed by clustering analyses, outlier analysis and t-tests of the drug sensitivity scores. We found robust correlations between BRAF-mutation status and response to BRAF-inhibitors, and lack of response to Fluorouracil and its prodrug Capecitabine for cell lines with microsatelite instability. These cell lines were sensitive to Topoisomerase I-inhibitors, such as Irinotecan, Valrubicin and Idarubicin. Cell lines with TP53wt were sensitive to the TP53-MDM2 interaction inhibitor Nutlin-3. We additionally identified a more potent novel TP53-MDM2 interaction inhibitor. Pharmacologic correlations for drug classes such as MEK-, EGFR-, Aurora A/B-, PI3K/AKT-, HSP90 and IGF1R-inhibitors were also found. Conclusions: A comprehensive drug screen of 36 CRC cell lines confirms pharmacogenomic relationships and reveals novel potentially relevant therapies for CRC.

Identification of Novel Fusion Genes in Testicular Germ Cell Tumors

Testicular germ cell tumors (TGCT) are the most frequently diagnosed solid tumors in young men ages 15 to 44 years. Embryonal carcinomas (EC) comprise a subset of TGCTs that exhibit pluripotent characteristics similar to embryonic stem (ES) cells, but the genetic drivers underlying malignant transformation of ECs are unknown. To elucidate the abnormal genetic events potentially contributing to TGCT malignancy, such as the existence of fusion genes or aberrant fusion transcript expression, we performed RNA sequencing of EC cell lines and their nonmalignant ES cell line counterparts. We identified eight novel fusion transcripts and one gene with alternative promoter usage, ETV6. Four out of nine transcripts were found recurrently expressed in an extended panel of primary TGCTs and additional EC cell lines, but not in normal parenchyma of the testis, implying tumor-specific expression. Two of the recurrent transcripts involved an intrachromosomal fusion between RCC1 and HENMT1 located 80 Mbp apart and an interchromosomal fusion between RCC1 and ABHD12B. RCC1-ABHD12B and the ETV6 transcript variant were found to be preferentially expressed in the more undifferentiated TGCT subtypes. In vitro differentiation of the NTERA2 EC cell line resulted in significantly reduced expression of both fusion transcripts involving RCC1 and the ETV6 transcript variant, indicating that they are markers of pluripotency in a malignant setting. In conclusion, we identified eight novel fusion transcripts that, to our knowledge, are the first fusion genes described in TGCT and may therefore potentially serve as genomic biomarkers of malignant progression.

Regulator of Chromosome Condensation 2 Identifies High-Risk Patients within Both Major Phenotypes of Colorectal Cancer

PURPOSE

Colorectal cancer has high incidence and mortality worldwide. Patients with microsatellite instable (MSI) tumors have significantly better prognosis than patients with microsatellite stable (MSS) tumors. Considerable variation in disease outcome remains a challenge within each subgroup, and our purpose was to identify biomarkers that improve prediction of colorectal cancer prognosis.

EXPERIMENTAL DESIGN

Mutation analyses of 42 MSI target genes were performed in two independent MSI tumor series (n = 209). Markers that were significantly associated with prognosis in the test series were assessed in the validation series, followed by functional and genetic explorations. The clinical potential was further investigated by immunohistochemistry in a population-based colorectal cancer series (n = 903).

RESULTS

We identified the cell-cycle gene regulator of chromosome condensation 2 (RCC2) as a cancer biomarker. We found a mutation in the 5' UTR region of RCC2 that in univariate and multivariate analyses was significantly associated with improved outcome in the MSI group. This mutation caused reduction of protein expression in dual luciferase gene reporter assays. siRNA knockdown in MSI colon cancer cells (HCT15) caused reduced cell proliferation, cell-cycle arrest, and increased apoptosis. Massive parallel sequencing revealed few RCC2 mutations in MSS tumors. However, weak RCC2 protein expression was significantly associated with poor prognosis, independent of clinical high-risk parameters, and stratifies clinically important patient subgroups with MSS tumors, including elderly patients (>75 years), stage II patients, and those with rectal cancer.

CONCLUSIONS

Impaired RCC2 affects functional and clinical endpoints of colorectal cancer. High-risk patients with either MSI or MSS tumors can be identified with cost-effective routine RCC2 assays.

Exome sequencing of bilateral testicular germ cell tumors suggests independent development lineages

Intratubular germ cell neoplasia, the precursor of testicular germ cell tumors (TGCTs), is hypothesized to arise during embryogenesis from developmentally arrested primordial germ cells (PGCs) or gonocytes. In early embryonal life, the PGCs migrate from the yolk sac to the dorsal body wall where the cell population separates before colonizing the genital ridges. However, whether the malignant transformation takes place before or after this separation is controversial. We have explored the somatic exome-wide mutational spectra of bilateral TGCT to provide novel insight into the in utero critical time frame of malignant transformation and TGCT pathogenesis. Exome sequencing was performed in five patients with bilateral TGCT (eight tumors), of these three patients in whom both tumors were available (six tumors) and two patients each with only one available tumor (two tumors). Selected loci were explored by Sanger sequencing in 71 patients with bilateral TGCT. From the exome-wide mutational spectra, no identical mutations in any of the three bilateral tumor pairs were identified. Exome sequencing of all eight tumors revealed 87 somatic non-synonymous mutations (median 10 per tumor; range 5-21), some in already known cancer genes such as CIITA, NEB, platelet-derived growth factor receptor α (PDGFRA), and WHSC1. SUPT6H was found recurrently mutated in two tumors. We suggest independent development lineages of bilateral TGCT. Thus, malignant transformation into intratubular germ cell neoplasia is likely to occur after the migration of PGCs. We reveal possible drivers of TGCT pathogenesis, such as mutated PDGFRA, potentially with therapeutic implications for TGCT patients.

Prognostic Significance of β-Catenin, E-Cadherin, and SOX9 in Colorectal Cancer: Results from a Large Population-Representative Series

Robust biomarkers that can precisely stratify patients according to treatment needs are in great demand. The literature is inconclusive for most reported prognostic markers for colorectal cancer (CRC). Hence, adequately reported studies in large representative series are necessary to determine their clinical potential. We investigated the prognostic value of three Wnt signaling-associated proteins, β-catenin, E-cadherin, and SOX9, in a population-representative single-hospital series of 1290 Norwegian CRC patients by performing immunohistochemical analyses of each marker using the tissue microarray technology. Loss of membranous or cytosolic β-catenin and loss of cytosolic E-cadherin protein expression were significantly associated with reduced 5-year survival in 903 patients who underwent major resection (722 evaluable tissue cores) independently of standard clinicopathological high-risk parameters. Pre-specified subgroup analyses demonstrated particular effect for stage IV patients for β-catenin membrane staining (P = 0.018; formal interaction test P = 0.025). Among those who underwent complete resection (714 patients, 568 evaluable), 5-year time-to-recurrence analyses were performed, and stage II patients with loss of cytosolic E-cadherin were identified as an independent high-risk subgroup (P = 0.020, formal interaction test was not significant). Nuclear β-catenin and SOX9 protein, regardless of intracellular location, were not associated with prognosis. In conclusion, the protein expression level of membranous or cytosolic β-catenin and E-cadherin predicts CRC patient subgroups with inferior prognosis.

Prognostic Significance of β-Catenin, E-Cadherin, and SOX9 in Colorectal Cancer: Results from a Large Population-Representative Series

Robust biomarkers that can precisely stratify patients according to treatment needs are in great demand. The literature is inconclusive for most reported prognostic markers for colorectal cancer (CRC). Hence, adequately reported studies in large representative series are necessary to determine their clinical potential. We investigated the prognostic value of three Wnt signaling-associated proteins, β-catenin, E-cadherin, and SOX9, in a population-representative single-hospital series of 1290 Norwegian CRC patients by performing immunohistochemical analyses of each marker using the tissue microarray technology. Loss of membranous or cytosolic β-catenin and loss of cytosolic E-cadherin protein expression were significantly associated with reduced 5-year survival in 903 patients who underwent major resection (722 evaluable tissue cores) independently of standard clinicopathological high-risk parameters. Pre-specified subgroup analyses demonstrated particular effect for stage IV patients for β-catenin membrane staining (P = 0.018; formal interaction test P = 0.025). Among those who underwent complete resection (714 patients, 568 evaluable), 5-year time-to-recurrence analyses were performed, and stage II patients with loss of cytosolic E-cadherin were identified as an independent high-risk subgroup (P = 0.020, formal interaction test was not significant). Nuclear β-catenin and SOX9 protein, regardless of intracellular location, were not associated with prognosis. In conclusion, the protein expression level of membranous or cytosolic β-catenin and E-cadherin predicts CRC patient subgroups with inferior prognosis.

Connexins in colorectal cancer pathogenesis

The connexins constitute a family of integral membrane proteins that form channels between adjacent cells. These channels are assembled in plasma membrane domains known as gap junctions and enable cells to directly exchange ions and small molecules. Intercellular communication via gap junctions plays important roles in regulating cell growth and differentiation and in maintaining tissue homeostasis. This type of cell communication is often impaired during cancer development, and several members of the connexin protein family have been shown to act as tumor suppressors. Emerging evidence suggests that the connexin protein family has important roles in colorectal cancer development. In the normal colonic epithelial tissue, three connexin isoforms, connexin 26 (Cx26), Cx32 and Cx43, have been shown to be expressed at the protein level. Colorectal cancer development is associated with loss of connexin expression or relocalization of connexins from the plasma membrane to intracellular compartments. Downregulation of connexins in colorectal carcinomas at the transcriptional level involves cancer-specific promoter hypermethylation. Recent studies suggest that Cx43 may constrain growth of colon cancer cells by interfering with the Wnt/β-catenin pathway. There is also increasing evidence that the connexins may have potential as prognostic markers in colorectal cancer. This review discusses the role of connexins in colorectal cancer pathogenesis, as well as their potential as prognostic markers and targets in the prevention and treatment of the disease.

The gap junction channel protein connexin 43 is covalently modified and regulated by SUMOylation

SUMOylation is a posttranslational modification in which a member of the small ubiquitin-like modifier (SUMO) family of proteins is conjugated to lysine residues in specific target proteins. Most known SUMOylation target proteins are located in the nucleus, but there is increasing evidence that SUMO may also be a key determinant of many extranuclear processes. Gap junctions consist of arrays of intercellular channels that provide direct transfer of ions and small molecules between adjacent cells. Gap junction channels are formed by integral membrane proteins called connexins, of which the best-studied isoform is connexin 43 (Cx43). Here we show that Cx43 is posttranslationally modified by SUMOylation. The data suggest that the SUMO system regulates the Cx43 protein level and the level of functional Cx43 gap junctions at the plasma membrane. Cx43 was found to be modified by SUMO-1, -2, and -3. Evidence is provided that the membrane-proximal lysines at positions 144 and 237, located in the Cx43 intracellular loop and C-terminal tail, respectively, act as SUMO conjugation sites. Mutations of lysine 144 or lysine 237 resulted in reduced Cx43 SUMOylation and reduced Cx43 protein and gap junction levels. Altogether, these data identify Cx43 as a SUMOylation target protein and represent the first evidence that gap junctions are regulated by the SUMO system.

Smad ubiquitination regulatory factor-2 controls gap junction intercellular communication by modulating endocytosis and degradation of connexin43

Gap junctions consist of arrays of intercellular channels that enable adjacent cells to communicate both electrically and metabolically. Gap junction channels are made of a family of integral membrane proteins called connexins, of which the best-studied member is connexin43. Gap junctions are dynamic plasma membrane domains, and connexin43 has a high turnover rate in most tissue types. However, the mechanisms involved in the regulation of connexin43 endocytosis and transport to lysosomes are still poorly understood. Here, we demonstrate by live-cell imaging analysis that treatment of cells with 12-O-tetradecanoylphorbol 13-acetate (TPA) induces endocytosis of subdomains of connexin43 gap junctions. The internalized, connexin43-enriched vesicles were found to fuse with early endosomes, which was followed by transport of connexin43 to the lumen of early endosomes. The HECT E3 ubiquitin ligase smad ubiquitination regulatory factor-2 (Smurf2) was found to be recruited to connexin43 gap junctions in response to TPA treatment. Depletion of Smurf2 by small interfering RNA (siRNA) resulted in enhanced levels of connexin43 gap junctions between adjacent cells and increased gap junction intercellular communication. Smurf2 depletion also counteracted the TPA-induced endocytosis and degradation of connexin43. Collectively, these data identify Smurf2 as a novel regulator of connexin43 gap junctions.

Connexin43 acts as a colorectal cancer tumor suppressor and predicts disease outcome

This article is the first to show that loss of connexin43 (Cx43) expression in colorectal tumors is correlated with significantly shorter relapse-free and overall survival. Cx43 was further found to negatively regulate growth of colon cancer cells, in part by enhancing apoptosis. In addition, Cx43 was found to colocalize with β-catenin and reduce Wnt signaling. The study represents the first evidence that Cx43 acts as a colorectal cancer tumor suppressor and that loss of Cx43 expression during colorectal cancer development is associated with reduced patient survival. The study has important implications for the assessment of Cx43 as a prognostic marker and target in colorectal cancer prevention and therapy. Gap junctions consist of intercellular channels that permit direct transfer of ions and small molecules between adjacent cells. The gap junction channel protein Cx43 plays important roles in cell growth control and differentiation and is frequently dysregulated in human cancers. However, the functional importance and clinical relevance of Cx43 in cancer development has remained elusive. Here, we show that Cx43 is downregulated or aberrantly localized in colon cancer cell lines and colorectal carcinomas, which is associated with loss of gap junction intercellular communication. The in situ protein expression of Cx43 was analyzed in colorectal tumors in a cohort of 674 patients and related to established clinicopathological variables and survival. A subgroup of the patients had weak or no expression of Cx43 in tumors. Loss of Cx43 expression was significantly correlated with shorter relapse-free and overall survival. Loss of Cx43 further identified a high-risk subgroup among stage I and stage II patients with reduced relapse-free and overall survival. Ectopic expression of Cx43 in the colon cancer cell line HT29 was associated with reduced growth in monolayer and soft agar cultures and in tumor xenografts. Cx43 was found to colocalize with β-catenin and negatively regulate the Wnt signaling pathway, and expression of Cx43 was associated with increased levels of apoptosis. Altogether, these data indicate that Cx43 is a colorectal cancer tumor suppressor protein that predicts clinical outcome.

Inhibition of connexin 43 gap junction channels by the endocrine disruptor ioxynil

Gap junctions are intercellular plasma membrane domains containing channels that mediate transport of ions, metabolites and small signaling molecules between adjacent cells. Gap junctions play important roles in a variety of cellular processes, including regulation of cell growth and differentiation, maintenance of tissue homeostasis and embryogenesis. The constituents of gap junction channels are a family of trans-membrane proteins called connexins, of which the best-studied is connexin 43. Connexin 43 functions as a tumor suppressor protein in various tissue types and is frequently dysregulated in human cancers. The pesticide ioxynil has previously been shown to act as an endocrine disrupting chemical and has multiple effects on the thyroid axis. Furthermore, both ioxynil and its derivative ioxynil octanoate have been reported to induce tumors in animal bioassays. However, the molecular mechanisms underlying the possible tumorigenic effects of these compounds are unknown. In the present study we show that ioxynil and ioxynil octanoate are strong inhibitors of connexin 43 gap junction channels. Both compounds induced rapid loss of connexin 43 gap junctions at the plasma membrane and increased connexin 43 degradation. Ioxynil octanoate, but not ioxynil, was found to be a strong activator of ERK1/2. The compounds also had different effects on the phosphorylation status of connexin 43. Taken together, the data show that ioxynil and ioxynil octanoate are potent inhibitors of intercellular communication via gap junctions.

Are Specific Antiretrovirals associated with an Increased Risk of Discontinuation due to Toxicities or Patient/Physician Choice in patients with Hepatitis C Virus Coinfection?

Background

Liver damage associated with hepatitis C (HCV) may influence the likelihood of experiencing discontinuation due to toxicities or patient/physician choice (TOXPC) in patients taking combination antiretroviral therapy (cART). Little information to address this concern is available from clinical trials as patients with HCV are often excluded.

Aims

To compare incidence rates of discontinuation due to TOXPC associated with specific antiretrovial drugs in patients with or without HCV.

Patients/methods

A total of 4929 patients from EuroSIDA under follow-up from January 1999 on a specific nucleoside pair (zidovudine/lamivudine, didanosine/stavudine, stavudine/lamivudine, or other) with a third drug (abacavir, nelfinavir, indinavir, nevirapine, efavirenz, lopinavir/ ritonavir or other boosted-protease inhibitor (PI)-containing regimen) and with known HCV serostatus were studied for the incidence of discontinuation of any nucleoside pair or third drug due to TOXPC. Incidence rate ratios were derived from Poisson regression models.

Results

In total 1358 patients had HCV (27.5%). During 12 799 person-years of follow-up there were 2141 discontinuations due to TOXPC for nucleoside pairs and 2501 for third drugs. The incidence of discontinuation due to TOXPC was consistently higher in patients with HCV after stratification by nucleoside pair or third drug. After adjustment for CD4+ count, gender, exposure group, time on HAART, region and treatment regimen, there were few differences in the rate of discontinuation due to TOXPC in those with HCV compared with those without for any nucleoside pairs or third drugs. Similar results were seen when concentrating on discontinuation due to toxicities alone.

Conclusions

Although patients with HCV generally had higher rates of discontinuation due to TOXPC compared with patients without HCV, there was little evidence to suggest that this was associated with any specific nucleoside pair or third drug used as part of cART. Our results do not suggest that any specific component of cART is more poorly tolerated in patients with HCV or that the presence of HCV should influence the choice between antiretrovirals used as part of a cART regimen.

Thymidine Analogue Mutation Profiles: Factors Associated with Acquiring Specific Profiles and their Impact on the Virological Response to Therapy

Background

Studies have suggested that HIV-1 may develop thymidine analogue mutations (TAMs) by one of two distinct pathways – the TAM1 pathway (including mutations 41L, 210W and 215Y) or the TAM2 pathway (including mutations 67N, 70R and 219E/Q) – under the pressure of a not fully suppressive thymidine-analogue-containing regimen.

Methods

Frozen plasma samples stored in the EuroSIDA repository were selected and sent to two central laboratories for genotypic analysis. We considered 733 patients with at least one genotypic test showing ≥1 TAMs (the first of these tests in chronological order was used). TAM1 and TAM2 genotypic profiles were defined in accordance with previous literature. Statistical modelling involved logistic regression and linear regression analysis for censored data.

Results

The observed frequencies of patterns classifiable as TAM1 or TAM2 profiles were markedly higher than the probabilities of falling into these classifications by chance alone. The chance of detecting a TAM2 profile increased by 25% per additional year of exposure to zidovudine. We found that mutations 67N and 184V were not associated with a particular TAM profile. In the presence of TAM2 profiles, the adjusted mean difference in the 6-month viral reduction was 0.96 log10 copies/ml (95% confidence interval: 0.20; 1.73) higher in patients who started stavudine-containing regimens instead of zidovudine-containing regimens.

Conclusions

This study provides evidence that the suggested TAM clustering is a real phenomenon and that it may be driven by which thymidine analogue the patients has used. In patients with TAM2-resistant viruses, stavudine appears to retain greater viral activity than zidovudine.

Baseline Resistance and Virological Outcome in Patients with Virological Failure who Start a Regimen Containing Abacavir: Eurosida Study

Objectives

To investigate the ability of several HIV-1 drug-resistance interpretation systems, as well as the number of pre-specified combinations of abacavir-related mutations, to predict virological response to abacavir-containing regimens in antiretroviral therapy-experienced, abacavir-naive patients starting an abacavir-containing regimen in the EuroSIDA cohort.

Patients and methods

A total of 100 HIV-infected patients with viral load (VL) >500 copies/ml who had a plasma sample available at the time of starting abacavir (baseline) were included. Resistance to abacavir was interpreted by using eight different commonly used systems that consisted of rules-based algorithms or tables of mutations. Correlation between baseline abacavir-resistance mutations and month 6 virological response was performed on this population using a multivariable linear regression model accounting for censored data.

Results

The baseline VL was 4.36 log10 RNA copies/ml [interquartile range (IQR): 3.65–4.99 log10 RNA copies/ml] and the median CD4 cell count was 210 cells/μl (IQR: 67–305 cells/μl). Our patients were pre-exposed to a median of seven antiretrovirals (2–12) before starting abacavir therapy. The median (range) number of abacavir mutations (according to the International AIDS Society-USA) detected at baseline was 3.5 (0–8). Overall, the Kaplan–Meier estimate of the median month 6 VL decline was 0.86 log10 RNA copies/ml [95% confidence intervals (95% CI): 0.45–1.24]. The VL in those patients ( n=31) who intensified treatment by adding only abacavir decreased by a median 0.20 log10 RNA copies/ml (95% CI: -0.18; +0.94). The proportion of patients who harboured viruses fully resistant to abacavir among the eight genotypic resistance interpretation algorithms ranged from 12% [Agence Nationale de Recherches sur le SIDA (ANRS)] to 79% [Stanford HIV RT and PR Sequence Database (HIVdb)]. Some interpretation systems showed statistically significant associations between the predicted resistance status and the virological response while others showed no consistent association. The number of active drugs in the regimen was associated with greater virological suppression (additional month 6 VL reduction per additional sensitive drug=0.51, 95% CI: 0.15–0.88, P=0.006); baseline VL was also weakly associated (additional month 6 VL reduction per log10 higher=0.30, 95% CI: -0.02; +0.62, P=0.06). In contrast, the number of drugs previously received was associated with diminished viral reduction (additional month 6 VL reduction per additional drug=-0.14, 95% CI: -0.28; 0.00, P=0.05).

Conclusions

Our results revealed a high degree of variability among several genotypic resistance interpretation algorithms currently in use for abacavir. Therefore, the interpretation of genotypic resistance for predicting response to regimens containing abacavir remains a major challenge.

Immunoglobulin levels amongst persons with and without human immunodeficiency virus type 1 infection in Uganda and Norway

CD4+-cell count and viral load monitoring are expensive and unavailable to most human immunodeficiency virus (HIV)-infected people in Africa. In an attempt to evaluate alternative methods for monitoring antiretroviral (ARV) therapy, we measured concentrations of immunoglobulin (Ig)A, IgM, IgG and IgG1 amongst adults with and without HIV in Uganda and Norway. We adjusted for disease severity by stratifying HIV-positive subjects on CD4+-cell counts above and below 200 cells/ micro l. Median serum levels of IgG, IgG1 and IgA were significantly higher in HIV-positive persons compared with HIV-negative persons in both countries (P < 0.001 and P = 0.018 for IgA in Ugandan patients). Levels of IgA in Ugandan HIV-negative subjects were significantly lower than those in HIV-positive subjects with low CD4+ compared with those with high CD4+-cell counts (P < 0.001 and P = 0.069, respectively). IgM levels were different between the HIV-negative and the two HIV-positive groups in Norway (P < 0.001). The mean levels of IgM, IgG and IgG1 in HIV-negative and -positive African subjects were generally higher than those in comparable groups of Western subjects. Our results verify that levels of IgA, IgG and IgG1 vary between HIV-negative and -positive individuals in both study populations. Their determination may be useful in monitoring both disease progression and response to ARV therapy.

Relationships of Efficiency to Reproductive Disorders in Danish Milk Production: A Stochastic Frontier Analysis

Relationships of various reproductive disorders and milk production performance of Danish dairy farms were investigated. A stochastic frontier production function was estimated using data collected in 1998 from 514 Danish dairy farms. Measures of farm-level milk production efficiency relative to this production frontier were obtained, and relationships between milk production efficiency and the incidence risk of reproductive disorders were examined. There were moderate positive relationships between milk production efficiency and retained placenta, induction of estrus, uterine infections, ovarian cysts, and induction of birth. Inclusion of reproductive management variables showed that these moderate relationships disappeared, but directions of coefficients for almost all those variables remained the same. Dystocia showed a weak negative correlation with milk production efficiency. Farms that were mainly managed by young farmers had the highest average efficiency scores. The estimated milk losses due to inefficiency averaged 1142, 488, and 256 kg of energy-corrected milk per cow, respectively, for low-, medium-, and high-efficiency herds. It is concluded that the availability of younger cows, which enabled farmers to replace cows with reproductive disorders, contributed to high cow productivity in efficient farms. Thus, a high replacement rate more than compensates for the possible negative effect of reproductive disorders. The use of frontier production and efficiency/inefficiency functions to analyze herd data may enable dairy advisors to identify inefficient herds and to simulate the effect of alternative management procedures on the individual herd's efficiency.

Risk factors for metritis in Danish dairy cows

A retrospective longitudinal study of metritis was conducted in Denmark on data collected during 1993-1994. Data on herd size, breed, parity, and treatment of disease were obtained from the Danish Cattle Database. Management and production-facility data were collected using a questionnaire, conducted as a telephone interview in 1994. The study included 2144 herds from three regions in Denmark (102,060 cows). Herd-level variables included were: herd size, housing, flooring, grazing, calving measures, and calving supervision. Cow-level variables were: parity, breed, calving season and whether the cow had been treated by a veterinarian for dystocia or the diseases: retained placenta, reproductive disease, ketosis, milk fever, or dry cow mastitis. Marginal multivariable logistic-regression analyses were performed. The cow with highest odds of metritis was a first or greater than or equal to third parity cow, of large breed, that calved during November-April, in a zero-grazing herd. The cow had been treated for dystocia, retained placenta, and at least one other reproductive disease, but not for ketosis.

Response to Antiretroviral Therapy among Patients Exposed to Three Classes of Antiretrovirals: Results from the Eurosida Study

There is an increasing proportion of HIV-positive patients exposed to all licensed classes of antiretrovirals, and the response to salvage regimens may be poor. Among over 8500 patients in EuroSIDA, the proportion of treated patients exposed to nucleosides, protease inhibitors (PIs) and non-nucleoside reverse transcriptase inhibitor (NNRTI) increased from 0% in 1996 to 47% in 2001. Four-hundred-and-thirteen patients, who had failed virologically two highly active antiretroviral therapy (HAART) regimens and experienced all three main drug classes, started a salvage regimen of at least three drugs, in which at least one new PI or NNRTI was included. Median viral load was 4.7 log copies/ml [Interquartile range (IQR) 4.2–5.2], CD4 lymphocyte count 150/mm3 (IQR 60–274/mm3) and follow-up 14 months. Of these patients, 283 (69%) subsequently experienced at least a 1 log decline in viral load and 202 (49%) achieved a viral load <500 copies/ml. Conversely, the CD4 count halved from the baseline value in 88 (21%), and 45 (11%) experienced a new AIDS-defining disease. In multivariable analyses, a 1 log viral load reduction was related to baseline viral load [relative hazard (RH) 1.27 per 1 log higher; P=0.008], a previous viral load of less than 500 copies/ml (RH 1.69; P=0.002), more recent initiation of the regimen (RH 1.36 per year more recent; P=0.02), number of new drugs in the regimen (RH 1.20 per drug; P=0.02), time since start of antiretroviral therapy (RH 0.94 per extra year; P=0.035) and time spent on HAART with viral load >1000 copies/ml (RH 0.96 per extra month; P=0.0001). Analysis of factors associated with CD4 count decline and new AIDS disease also indicated improved outcomes in more recent times and a tendency for a better response in those starting more new drugs, but no relationship with the total number of drugs. Outcomes in people starting salvage regimens appear to depend on the number of new drugs started but not on the total number of drugs being used.

Estrogen receptors in the human male prostatic urethra and prostate in prostatic cancer and benign prostatic hyperplasia

Estrogen receptors (ERs) in the prostate and prostatic urethra were examined in 33 men with benign prostatic hyperplasia (BPH) and in 11 with prostate cancer (PC). The Abbot monoclonal ER-ICA assay was used for immunohistochemical investigation. In the BPH group, ERs were revealed in the prostatic stroma in eight cases and in the glandular epithelium in one. In four cases ERs were seen in the prostatic stroma and in the glandular epithelium. In the prostatic urethra, ERs were found in 19 cases located in the urothelium, lamina propria and/or periurethral glands. In the PC group, ERs were demonstrated in the prostatic stroma and/or prostatic urethra in 6 out of 11 cases. In both BPH and PC patients, immunoreactivity was weak and confined to few cells, indicating low ER content in the prostate as well as in the prostatic urethra. Dextran-coated charcoal (DCC) analysis was used for detection and quanticization of cytosolic and nuclear ERs. In the BPH group, ERs were detected once in the prostate and prostatic urethra in the nuclear and cytosol, and additionally in the prostatic urethra in the cytosol fraction in three cases. In all cases, ER content was low, ranging from 10-15 fmol/mg protein. In the PC group, ERs were detected in the prostatic urethra and/or prostate in the cytosol fraction from two patients. The contents were low, ranging from 10-13 fmol/mg protein. We conclude that in human BPH and PC, ERs can be present in the prostate and prostatic urethra. In the prostate, ERs are mainly located in the stroma, but in BPH specimens they can also be found in the glandular epithelium. Biochemically, the use of the DCC analysis is of limited value, since ER content in the human prostate and prostatic urethra is at the limit of detection with this method.

Amlodipine dynamic effects and myocardial pharmacokinetics in the isolated and perfused guinea-pig heart

Myocardial dynamic effects and pharmacokinetics of amlodipine were studied in the isolated retrogradely perfused and spontaneously beating guinea-pig heart. Pharmacokinetic analysis of drug accumulation showed one-compartment characteristics with an half-life of 76 min. Whereas disposition exhibited two-compartment characteristics with phasic half-lives of 25 and 174 min., respectively. Myocardial drug accumulation was increased by 600 times at steady-state compared to the perfusion liquid. Dynamic effect parameters were studied during increasing amlodipine concentrations from 0.16 to 220 nM. Dynamic steady-states developed within 20 min. Coronary flow-rate increased with an Emax of 119% and an EC50 of 1.2 x 10(-8) M. Amlodipine produced inhibitory effects on contraction amplitude and velocities of contraction and relaxation. Observed Emax-values and curve-fitted EC50-values were: 97, 97 and 94% and 1.10(-8), 7.7 x 10(-9) and 2.1 x 10(-8) M, respectively. Heart frequency was not changed. Oxygen consumption increased markedly to a maximum of 44% at 3 x 10(-8) M amlodipine and then decreased to nearly initial values. The frequency-corrected QT-interval decreased to a maximal extent of 20% at the three highest concentrations. Myocardial efficiency expressed as the ratio of contraction velocity times frequency to oxygen consumption exhibited a progressive decline to about 2% of initial values. The PQ-interval was not changed and the QRS-interval showed only a small but significant decrease at the highest amlodipine concentration. No arrythmogenic effects were observed. The study demonstrated a very slow accumulation and disposition of amlodipine in the guinea-pig heart with a steady-state myocardial drug concentrating accumulation of 600 times. Marked increase in coronary flow-rate and oxygen consumption accompanied by a progressive negative inotropic effect were observed.