Clonal and "Intrinsic" Heterogeneity of Somatic Variants in Microsatellite-Stable Colorectal Carcinomas and Their Metastases.

To test the traditional model of tumor progression, Darwinian-type evolution, against the more recent Big Bang model, we selected 6 microsatellite-stable colorectal standard-type adenocarcinomas and their synchronous lymph node and liver metastases. Somatic genomic variants were identified by whole-exome sequencing (WES) of large tumor fragments from the primaries and 1 liver metastasis each, and used to design targeted resequencing next-generation sequencing (NGS) panels, 1 per case. Targeted deep resequencing (mean coverage, 2725; median, 2222) was performed with DNA from punch samples (1-mm tissue microarrayer needles) obtained from different regions of the primaries and their metastases. In total, 255 genomic variants were interrogated in 108 punch samples. Clonal heterogeneity was infrequent: a pattern of clonal heterogeneity consistent with a role in metastasis formation was observed only in 1 case in a single gene (p. Asp604Tyr of the PTPRT gene). However, when comparing variant allele frequencies (VAFs) of genomic variants in adjacent positions on chromosomes ("matched genomic variant loci") across punch samples, differences that exceeded 2 SD of the NGS assay variations (ad hoc dubbed VAF dysbalance) were observed in 7.1% of the punch samples (2.6%-12.0% per case), which indicates an intricate intermixing of mutated and nonmutated tumor cells ("intrinsic heterogeneity"). Additional OncoScan array analyses on a subset of the punch samples (31 in total) showed gross genomic aberrations as a possible explanation in only some (39.2%) of the matched genomic variant loci with VAF dysbalance. Our study provides a fairly direct (statistical model-free) view of the genomic states of microsatellite-stable colorectal carcinomas and their metastases, and suggests that Darwinian-type tumor evolution is not the key pathway of the metastasizing disease; instead, we recorded an "intrinsic" genomic heterogeneity, which may echo an initial Big Bang-like event.

ROCK2 inhibition triggers the collective invasion of colorectal adenocarcinomas.

The metastatic progression of cancer is a multi-step process initiated by the local invasion of the peritumoral stroma. To identify the mechanisms underlying colorectal carcinoma (CRC) invasion, we collected live human primary cancer specimens at the time of surgery and monitored them ex vivo. This revealed that conventional adenocarcinomas undergo collective invasion while retaining their epithelial glandular architecture with an inward apical pole delineating a luminal cavity. To identify the underlying mechanisms, we used microscopy-based assays on 3D organotypic cultures of Caco-2 cysts as a model system. We performed two siRNA screens targeting Rho-GTPases effectors and guanine nucleotide exchange factors. These screens revealed that ROCK2 inhibition triggers the initial leader/follower polarization of the CRC cell cohorts and induces collective invasion. We further identified FARP2 as the Rac1 GEF necessary for CRC collective invasion. However, FARP2 activation is not sufficient to trigger leader cell formation and the concomitant inhibition of Myosin-II is required to induce invasion downstream of ROCK2 inhibition. Our results contrast with ROCK pro-invasive function in other cancers, stressing that the molecular mechanism of metastatic spread likely depends on tumour types and invasion mode.

NSG mice as hosts for oncological precision medicine.

Patient-derived xenograft (PDX) models have been rediscovered as meaningful research tool. By using severely immunodeficient mice, high-engraftment rates can be theoretically achieved, permitting clinical stratification strategies. Apart from engraftment efficacy, tolerability towards certain cytostatic drugs varies among individual mouse strains thus impeding large-scale screenings. Here, we aimed at optimizing an in vivo treatment schedule using the widely applied cytostatic drug 5-fluoruracil (5-FU) for exemplary response prediction in colorectal cancer (CRC) PDX models. Four different individual CRC PDX models were engrafted into NOD.Cg-PrkdcscidIl2rgtm1Wjl (NSG) mice. Mice with established PDX were allocated to different treatment groups, receiving 5-FU, the oral prodrug Capecitabine, or 5-FU/leucovorin (LV) at different doses. Body weight, tumor size, and general behavior were assessed during therapy. Ex vivo analyses were done from blood samples, liver, as well as tumor resection specimen. Engraftment efficacy was high as expected in NSG mice, yielding stable PDX growth for therapy stratification. However, overall tolerability towards 5-FU was unexpectedly low, whereas the prodrug Capecitabine as well as the combination of 5-FU/LV at low doses were well tolerated. Accompanying plasma level determination of DYPD, the rate-limiting enzyme for 5-FU-mediated toxicity, revealed reduced activity in NSG mice compared with other common laboratory mouse strains, offering a likely explanation for the drug incompatibility. Also, the De Ritis quotient was highly elevated in treated mice, reflecting overall organ injury even at low doses. Summarizing these findings, NSG mice are ideal hosts for in vivo engraftment studies. However, the complex immunodeficiency reduces tolerance to certain drugs, thus making those mice especially sensitive. Consequently, such dose finding and tolerance tests constitute a necessity for similar cancer precision medicine approaches.

High mutational burden in colorectal carcinomas with monoallelic POLE mutations: absence of allelic loss and gene promoter methylation.

Hypermutator-type colorectal carcinomas are microsatellite-stable and have point mutations of the exonuclease domain of the DNA polymerase ε or δ genes (POLE and POLD1, respectively), and an ultrahigh tumor mutational burden (TMB). These tumors may be associated with enhanced antitumor immunity and preferentially afflict younger patients, but this notion awaits validation by accrual of further cases for detailed correlative phenotypic and molecular study. We performed POLE and POLD1 exonuclease domain Sanger sequencing of 271 unselected colorectal carcinomas. We identified two microsatellite-stable tumors with somatic POLE p.P286R variants, both with ultrahigh TMBs as demonstrated by whole exome sequencing. A POLE p.V411L was found in another two microsatellite-stable tumors with ultrahigh TMBs. Two of these four tumors were from young patients (<50 years old, nonsyndromic), and there was seen a prominent T-cell infiltration in three of them. Furthermore, a somatic POLE p.A465T was found in a Lynch-associated tumor, which, hypothetically, might have enhanced TMB (which was the highest of all). In two tumors, a somatic POLE p.V411L and a POLD1 p.E279K, respectively, were found only focally, and TMBs were low. It is commonly assumed that compromise of one allele is sufficient, but this has not been specifically addressed. Therefore, resequencing of the POLE or POLD1 mutations was done with DNA from tumor cells isolated by laser-capture microdissection. This demonstrated that the mutations were monoallelic, and there was no evidence of a "second hit", neither by allelic loss (allelotyping with polymorphic microsatellite markers), nor by promoter methylation (Pyromark CpG assays). Taken together, including at least the more common DNA polymerase mutations in NGS panels allows for straightforward identification of hypermutator-type colorectal carcinomas which often may be "immunoreactive". This is important at least in young patients or when a metastasizing stage of disease has been reached and immune-checkpoint therapy enters deliberation.

Suspected Hereditary Cancer Syndromes in Young Patients: Heterogeneous Clinical and Genetic Presentation of Colorectal Cancers.

Colorectal cancer (CRC) is rare in young patients without a confirmed family history of cancer. Reports of an increased prevalence of POLD1/POLE mutations in young patients with colorectal cancer have raised awareness and support routine genetic testing for patients with early-onset tumors. In cases of CRC without proven MMR-germline mutation, molecular analyses are warranted to confirm or rule out other familial CRC syndromes. This article describes the cases of two young male patients, who presented with locally advanced and metastatic CRC, and reports the results of the germline mutational analyses done for both patients. These cases demonstrate the importance of special care and molecular diagnostic procedures for young patients with CRC. KEY POINTS: Patients with colorectal cancer who are younger than 50 years at initial diagnosis (early onset) should routinely undergo genetic testing.Early- and very-early-onset patients (younger than 40 years) with absence of microsatellite instability should be considered for tumor mutation burden testing and/or DNA polymerase proofreading mutation.The mutational signature of HSP110 within mismatch repair deficiency-related tumors may help to identify patients likely to benefit from 5-fluorouracil-based chemotherapy.Intensified, maintained, and specific surveillance may help to reduce secondary tumor progression.

Engraftment Efficiency after Intra-Bone Marrow versus Intravenous Transplantation of Bone Marrow Cells in a Canine Nonmyeloablative Dog Leukocyte Antigen-Identical Transplantation Model.

An intra-bone marrow (IBM) hematopoietic stem cell transplantation (HSCT) is assumed to optimize the homing process and therefore to improve engraftment as well as hematopoietic recovery compared with conventional i.v. HSCT. This study investigated the feasibility and efficacy of IBM HSCT after nonmyeloablative conditioning in an allogeneic canine HSCT model. Two study cohorts received IBM HSCT of either density gradient (IBM-I, n = 7) or buffy coat (IBM-II, n = 6) enriched bone marrow cells. An historical i.v. HSCT cohort served as control. Before allogeneic HSCT experiments were performed, we investigated the feasibility of IBM HSCT by using technetium-99m marked autologous grafts. Scintigraphic analyses confirmed that most IBM-injected autologous cells remained at the injection sites, independent of the applied volume. In addition, cell migration to other bones occurred. The enrichment process led to different allogeneic graft volumes (IBM-I, 2 × 5 mL; IBM-II, 2 × 25 mL) and significantly lower counts of total nucleated cells in IBM-I grafts compared with IBM-II grafts (1.6 × 108/kg versus 3.8 × 108/kg). After allogeneic HSCT, dogs of the IBM-I group showed a delayed engraftment with lower levels of donor chimerism when compared with IBM-II or to i.v. HSCT. Dogs of the IBM-II group tended to reveal slightly faster early leukocyte engraftment kinetics than intravenously transplanted animals. However, thrombocytopenia was significantly prolonged in both IBM groups when compared with i.v. HSCT. In conclusion, IBM HSCT is feasible in a nonmyeloablative HSCT setting but failed to significantly improve engraftment kinetics and hematopoietic recovery in comparison with conventional i.v. HSCT.

Frameshift mutational target gene analysis identifies similarities and differences in constitutional mismatch repair-deficiency and Lynch syndrome.

Mismatch-repair deficient (MMR-D) malignancies include Lynch Syndrome (LS), which is secondary to germline mutations in one of the MMR genes, and the rare childhood-form of constitutional mismatch repair-deficiency (CMMR-D); caused by bi-allelic MMR gene mutations. A hallmark of LS-associated cancers is microsatellite instability (MSI), characterized by coding frameshift mutations (cFSM) in target genes. By contrast, tumors arising in CMMR-D patients are thought to display a somatic mutation pattern differing from LS. This study has the main goal to identify cFSM in MSI target genes relevant in CMMR-D and to compare the spectrum of common somatic mutations, including alterations in DNA polymerases POLE and D1 between LS and CMMR-D. CMMR-D-associated tumors harbored more somatic mutations compared to LS cases, especially in the TP53 gene and in POLE and POLD1, where novel mutations were additionally identified. Strikingly, MSI in classical mononucleotide markers BAT40 and CAT25 was frequent in CMMR-D cases. MSI-target gene analysis revealed mutations in CMMR-D-associated tumors, some of them known to be frequently hit in LS, such as RNaseT2, HT001, and TGFßR2. Our results imply a general role for these cFSM as potential new drivers of MMR-D tumorigenesis.

The PD-1 expressing immune phenotype of T cell exhaustion is prominent in the 'immunoreactive' microenvironment of colorectal carcinoma.

AIMS: This study was designed to test programmed cell death 1 (PD-1) expression of T cells, the hallmark of T cell exhaustion, in different 'immune-classes' of colorectal carcinoma microenvironments as delineated by unsupervised hierarchical cluster analysis. METHODS AND RESULTS: A tissue microarray was made with punches from the invasive margins of 40 microsatellite-unstable and 34 microsatellite-stable colorectal carcinomas. Immune cells were phenotyped by CD8, granzyme B, CD4, FoxP3, CD68, S-100, PD-1 and programmed cell death ligand 1 (PD-L1) immunohistochemistry; tumour area per tissue spot was quantified by cytokeratin (CK)18 immunohistochemistry. For each tissue spot, intra-epithelial immune cells were counted and densities of the various immune cells were calculated. Unsupervised hierarchical cluster analysis with these data yielded a group of 'anergic/immune-naive' microenvironments (47.3%), a group of 'intermediates' (27.0%) and a group of 'immunoreactives' (25.7%) in which PD-1 expressing T cells were prominent. Sixteen of 19 tissue spots representing immunoreactive microenvironments derived from microsatellite-unstable tumours and three were from microsatellite-stable tumours. Further phenotyping of intra-epithelial T cells by sequential immunohistochemistry showed frequent granzyme B/CD8 co-expression, whereas PD-1/CD8 co-expression was more variable. Using receiver operating curve (ROC) analysis, assignment to immune classes was seen to be feasible with good sensitivity and specificity by CD8 counts only. CONCLUSION: A subset of colorectal carcinoma microenvironments is distinguished from the rest by an immune cell composition suggestive of active host anti-tumour immune defence, but this appears to be antagonized by a brisk undercurrent of T cell exhaustion. This observation may have implications for selecting colorectal carcinoma patients for immune checkpoint therapy.

Tumor regression in rectal cancer after intensified neoadjuvant chemoradiation: a morphometric and clinicopathological study.

BACKGROUND: High interobserver variation is a well known drawback of conventional tumor regression grading, and reaching consensus among pathologists may require a considerable effort. Therefore, in this study, morphometry was tried to assess tumor regression, and its prognostic role was explored. METHODS: Tumor regression was quantified by a point counting method to yield tumor area fraction (TAF) as an index of remaining vital tumor. RESULTS: In a series of 104 patients with clinically advanced rectal cancer treated with neoadjuvant radiochemotherapy, TAFs were distributed continuously towards complete regression which was observed in 8.7% of the cases. Plotting TAFs grouped by a conventional regression grading (Dworak's) revealed considerable overlap between groups. In a control series of untreated cancers, only TAFs of cancers with an expansive invasive border were setoff clearly from TAFs obtained for the study cases, but TAFs of control cases with an infiltrative invasive border and mucinous carcinomas extended well into the range of TAFs recorded for regressing tumors. Locoregional recurrence (N = 10) was significantly associated with perineural tumor infiltration and capsule transgressing lymph node metastasis/tumor deposits but not with the degree of tumor regression. Overall survival was better for patients with major regressions (≤20th percentile by morphometry, or Dworak regression grade (DRG) 4/5), although statistical significance was not reached. CONCLUSIONS: Morphometry of tumor regression is feasible and explains why conventional regression grading is so difficult to perform. Assessment of tumor regression, by subjective grading or morphometry, does not appear to convey major prognostic information, at least not substantially beyond histopathological tumor staging. This observation discourages expending too much effort on developing this aspect of the pathomorphological workup of the resection specimens.

Urinary Retention Due to Severe Pseudocystic Mucoid Degeneration of the Prostatic Matrix: A Rare Urologic Manifestation of Cystic Fibrosis.

Cystic fibrosis (CF) is an autosomal recessive genetic disease, which is characterized by the production of thick mucus in exocrine glands. The main cause for morbidity and mortality in CF patients is respiratory failure. The gastrointestinal system is also commonly affected. Urologic manifestations of CF include infertility and azoospermia, nephrolithiasis, and stress urinary incontinence. In this report, we describe a 33-year-old male, who presented with recurrent urinary retention due to prostatic enlargement despite his young age. After transurethral resection, the voiding problems resolved. Histopathological examination, however, revealed a severe pseudocystic mucoid degeneration of the prostatic matrix as a cause of his subvesical obstruction. Although these structural changes are most probably due to his underlying disease, detailed histologic features have not been described in the literature.

Prognosis of rectal cancer patients improves with downstaging by intensified neoadjuvant radiochemotherapy - a matched pair analysis.

BACKGROUND: Neoadjuvant radiochemotherapy has been proven superior to adjuvant treatment in reducing the rate of local recurrence without impairing cancer related survival or the incidence of distant metastases in standard protocols of neoadjuvant radiochemotherapy. The present study aimed at addressing the effects of an intensified neoadjuvant radiochemotherapy on long term cancer related and disease free survival. METHODS: A total of 387 patients underwent oncologic resection for rectal cancer in our institution between January 2000 and December 2009. There were 106 patients (27.4%) who received an intensified radiochemotherapy protocol completely and without excluding criteria (study group). A matched pair analysis was performed by comparing the study group with patients undergoing primary surgery and postoperative radiochemotherapy, if necessary and possible (control group). Matching was carried out in descending order for UICC stage, R-status, tumor height, T-, N-, V-, L-, M- and G-category of the TNM-system according to the histopathological staging. Follow-up data included local recurrence rate, cancer related and disease free survival. RESULTS: In the study group histopathological work-up of the specimen revealed a treatment response in terms of tumor regression in 92.5% (98/106) of these patients. Undergoing intensified neoadjuvant RCT the actuarial cancer related and disease free survival was 67.9% and 70.4%, local recurrence was 5.7% after an observation period of 4.3 ± 2.55 years. In the control group cancer related and disease free survival was 71.7% and 82.7%, local recurrence was 4.7% after an observation period of 3.8 ± 3.05 years revealing no statistical significant difference between the two groups. Moreover, estimated 5-year results of cancer related survival (66.7% vs 67.9% (controls)), the disease free survival (66.7% vs 79.9% (controls)) as well as subgroup analysis of UICC 0-III and UICC IV patients showed no difference between the study and control group as well. CONCLUSION: In our study, intensified neoadjuvant radio-chemotherapy shows a high rate of tumor regression. The resulting inferior histopathological tumor stage shows the same long term local control and systemic tumor control as the control group with a primary more favorable tumor stage.

The "North German Tumor Bank of Colorectal Cancer": status report after the first 2 years of support by the German Cancer Aid Foundation.

PURPOSE: Research projects and clinical trials strongly rely on high-quality biospecimens which are provided by biobanks. Since differences in sample processing and storage can strongly affect the outcome of such studies, standardization between biobanks is necessary to guarantee reliable results of large, multicenter studies. The German Cancer Aid Foundation (Deutsche Krebshilfe e.V.) has therefore initiated the priority program "tumor tissue banks" in 2010 by funding four biobank networks focusing on central nervous system tumors, melanomas, breast carcinomas, and colorectal carcinomas. The latter one, the North German Tumor Bank of Colorectal Cancer (ColoNet) is managed by surgeons, pathologists, gastroenterologists, oncologists, scientists, and medical computer scientists. METHODS AND RESULTS: The ColoNet consortium has developed and harmonized standard operating procedures concerning all biobanking aspects. Crucial steps for quality assurance have been implemented and resulted in certification according to DIN EN ISO 9001. A further achievement is the construction of a web-based database for exploring available samples. In addition, common scientific projects have been initiated. Thus, ColoNet's repository will be used for research projects in order to improve early diagnosis, therapy, follow-up, and prognosis of colorectal cancer patients. Apart from the routine sample storage at -170 °C, the tumor banks' unique characteristic is the participation of outpatient clinics and private practices to further expand the sample and clinical data collection. CONCLUSION: The first 2 years of funding by the German Cancer Aid Foundation have already led to a closer scientific connection between the participating institutions and to a substantial collection of biospecimens obtained under highly standardized conditions.

Intensified neoadjuvant radiochemotherapy for rectal cancer enhances surgical complications.

BACKGROUND: Neoadjuvant radiochemotherapy has proven superior to adjuvant treatment in reducing the rate of local recurrence without impairing cancer related survival or the incidence of distant metastases. The present study aimed at addressing the effects of an intensified protocol of neoadjuvant treatment on the development of postoperative complications. METHODS: A total of 387 patients underwent oncological resection for rectal cancer in our institution between January 2000 and December 2009. 106 patients received an intensified radiochemotherapy. Perioperative morbidity and mortality were analyzed retrospectively with special attention on complication rates after intensified radio-chemotherapy. Therefore, for each patient subjected to neoadjuvant treatment a patient without neoadjuvant treatment was matched in the following order for tumor height, discontinuous resection/exstirpation, T-category of the TNM-system, dividing stoma and UICC stage. RESULTS: Of all patients operated for rectal cancer, 27.4% received an intensified neoadjuvant treatment. Tumor location in the matched patients were in the lower third (55.2%), middle third (41.0%) and upper third (3.8%) of the rectum. Postoperatively, surgical morbidity was higher after intensified neoadjuvant treatment. In the subgroup with low anterior resection (LAR) the anastomosis leakage rate was higher (26.6% vs. 9.7%) and in the subgroup of patients with rectal exstirpations the perineal wound infection rate was increased (42.2% vs. 18.8%) after intensified radiochemotherapy. CONCLUSIONS: In rectal cancer the decision for an intensified neoadjuvant treatment comes along with an increase of anastomotic leakage and perineal wound infection. Quality of life is often reduced considerably and has to be balanced against the potential benefit of intensifying neoadjuvant radiochemotherapy.

Establishment, characterization, and drug screening of low-passage patient individual non-small cell lung cancer in vitro models including the rare pleomorphic subentity.

Introduction: For pre-clinical drug development and precision oncology research, robust cancer cell models are essential. Patient-derived models in low passages retain more genetic and phenotypic characteristics of their original tumors than conventional cancer cell lines. Subentity, individual genetics, and heterogeneity greatly influence drug sensitivity and clinical outcome. Materials and methods: Here, we report on the establishment and characterization of three patient-derived cell lines (PDCs) of different subentities of non-small cell lung cancer (NSCLC): adeno-, squamous cell, and pleomorphic carcinoma. The in-depth characterization of our PDCs included phenotype, proliferation, surface protein expression, invasion, and migration behavior as well as whole-exome and RNA sequencing. Additionally, in vitro drug sensitivity towards standard-of-care chemotherapeutic regimens was evaluated. Results: The pathological and molecular properties of the patients' tumors were preserved in the PDC models HROLu22, HROLu55, and HROBML01. All cell lines expressed HLA I, while none were positive for HLA II. The epithelial cell marker CD326 and the lung tumor markers CCDC59, LYPD3, and DSG3 were also detected. The most frequently mutated genes included TP53, MXRA5, MUC16, and MUC19. Among the most overexpressed genes in tumor cells compared to normal tissue were the transcription factors HOXB9, SIM2, ZIC5, SP8, TFAP2A, FOXE1, HOXB13, and SALL4; the cancer testis antigen CT83; and the cytokine IL23A. The most downregulated genes on the RNA level encode the long non-coding RNA LANCL1-AS1, LINC00670, BANCR, and LOC100652999; the regulator of angiogenesis ANGPT4; the signaling molecules PLA2G1B and RS1; and the immune modulator SFTPD. Furthermore, neither pre-existing therapy resistances nor drug antagonistic effects could be observed. Conclusion: In summary, we successfully established three novel NSCLC PDC models from an adeno-, a squamous cell, and a pleomorphic carcinoma. Of note, NSCLC cell models of the pleomorphic subentity are very rare. The detailed characterization including molecular, morphological, and drug-sensitivity profiling makes these models valuable pre-clinical tools for drug development applications and research on precision cancer therapy. The pleomorphic model additionally enables research on a functional and cell-based level of this rare NCSLC subentity.

Microdensitometry of osteopontin as an immunohistochemical prognostic biomarker in colorectal carcinoma tissue microarrays: potential and limitations of the method in 'biomarker pathology'.

AIMS: To explore the potential and limitations of 'biomarker pathology' with quantitative immunohistochemistry on tissue microarrays, taking osteopontin and colorectal carcinoma as a model system. METHODS AND RESULTS: Microdensitometry for quantitative evaluation of osteopontin immunohistochemistry (clone OP3N) on digital microphotographs using the public domain software ImageJ was observed to be straightforward to perform and reliable. However, using colorectal carcinoma cell lines (n = 11) the correlation between densitometric evaluations of Western blots and microdensitometry of immunocytochemistry of slide cultures was only moderate. A virtual resampling method to simulate tissue microarrays showed that, due to heterogeneity of immunostaining, tumours were misclassified in nearly 20% of the arrays, even if four punches were used. With regard to prognosis, microdensitometric evaluation of a tissue microarray made of a clinicopathologically well-characterized series of colorectal carcinomas with long-term follow-up (222 cases evaluable in the tissue microarray, UICC Stages I-III/R0) showed a moderate survival advantage of patients with high osteopontin expression by microdensitometry. CONCLUSIONS: These results challenge the basic assumption that microdensitometry is a precise technique for the quantification of proteins detected by immunohistochemistry and delineate drawbacks encountered when working with tissue microarrays in clinicopathological studies.

A novel sialyl Le(X) expression score as a potential prognostic tool in colorectal cancer.

BACKGROUND: Treatment decisions in colorectal cancer subsequent to surgery are based mainly on the TNM system. There is a need to establish novel prognostic markers based on the molecular characterization of tumor cells. Evidence exists that sialyl Le(X) expression is correlated with an unfavorable outcome in colorectal cancer. The aim of this study was to establish a simple sialyl Le(X) staining score and to determine a potential correlation with the prognosis in a series of advanced colorectal carcinoma patients. METHODS: In order to implement routine use of sialyl Le(X) immunohistology, we established a new, easily reproducible score and defined a cutoff which discriminated groups with better or worse outcome, respectively. We then correlated sialyl Le(X) expression of 215 UICC stage III and IV patients with disease-free and cancer-related survival. RESULTS: A five-stage score could be established based on automated immunohistochemical stainings. Using a statistical model, we calculated a cutoff to discriminate between weak and strong staining positivity of sialyl Le(X). Patients with strong positive specimens had a worse cancer-related survival (P = 0.004) but no difference was observed for disease-free survival (P = 0.352). CONCLUSIONS: These results demonstrate a strong correlation between high sialyl Le(X)-expression in colorectal carcinomas and cancer-related survival. Our highly standardized and easy-to-use staining score is suitable for routine use and hence it could be recommended to evaluate sialyl Le(X)-expression as part of the standard histopathological analysis of colorectal carcinomas and to validate the score prospectively based on a larger population.

HROP68: A rare case of medullary pancreatic cancer-characterization and chemosensitivity of the first patient-derived cell line.

Introduction: Medullary pancreatic carcinoma (MPC) is a rare subtype of pancreatic ductal adenocarcinoma. MPCs represent less than 1% of all pancreatic cancers, and, with only 26 cases in the literature, knowledge regarding drug response and treatment outcome is very limited. Material and methods: We present the case of a 64-year-old male patient with MPC who was treated by left pancreatic resection and adjuvant chemotherapy. Due to local recurrence, the patient underwent intended curative reoperation. From both surgical specimens, patient-derived xenografts (PDXs) and, from the recurrence, a patient-derived cell line (PDCL) were established. We subsequently performed an in-depth characterization of this cell line including phenotypic characterization, surface protein expression, growth, and migratory performance as well as mutational analysis using whole-exome sequencing (WES). Additionally, in vitro drug sensitivity toward the standard-of-care chemotherapeutic regimen and selected targeted therapies was evaluated. Results: The pathological and molecular properties of this rare MPC case observed in the patient's tumors are preserved in the corresponding PDX and the PDCL of HROP68Tu2. Despite displaying an "immunogenic phenotype" with marked T-cell infiltration and a high-level expression of HLA II and Programmed death-ligand 1 (PD-L1), molecular analysis revealed microsatellite stability but a multitude of mutations affecting KRAS, TP53, KAT6B, FOXG1, RUNX1, and GRIK2 among others. Furthermore, HROP68Tu2 cells were susceptible toward 5-FU, irinotecan, oxaliplatin, gemcitabine, paclitaxel, and erlotinib as single agents, but only a moderate synergistic response was seen to the drugs of the FOLFIRINOX regimen. Even worse, the drugs of the two combinations gemcitabine plus paclitaxel and gemcitabine plus erlotinib showed antagonistic effects. Moreover, lapatinib, PRIMA-Met1, and olaparib selected as targeted therapeutics according to the mutational profiles and protein expression inhibited HROP68Tu2 cells' growth. Conclusion: This study illustrates the establishment of the first preclinical MPC models as well as the first in-depth characterization of an MPC PDCL. Since the scientific and clinical knowledge of this rare pancreatic cancer type is very limited, the presented models contribute to a better understanding of MPC and might be a valuable tool for the development of future treatment options.