[State of the Art Rectal Surgery]. / State of the Art Rektumchirurgie.

The multimodal treatment of rectal cancer has differentiated considerably over the last decade depending on the characteristics of the tumor and the patient's circumstances. Surgery continues to be an important pillar of therapy, the quality of which is of prognostic relevance for affected patients. This review provides an up-to-date overview of the indications for the various surgical procedures, current developments in perioperative management and the timing of surgery.

Molecular differences of angiogenic versus vessel co-opting colorectal cancer liver metastases at single-cell resolution.

BACKGROUND: Colorectal cancer liver metastases (CRCLM) are associated with a poor prognosis, reflected by a five-year survival rate of 14%. Anti-angiogenic therapy through anti-VEGF antibody administration is one of the limited therapies available. However, only a subgroup of metastases uses sprouting angiogenesis to secure their nutrients and oxygen supply, while others rely on vessel co-option (VCO). The distinct mode of vascularization is reflected by specific histopathological growth patterns (HGPs), which have proven prognostic and predictive significance. Nevertheless, their molecular mechanisms are poorly understood. METHODS: We evaluated CRCLM from 225 patients regarding their HGP and clinical data. Moreover, we performed spatial (21,804 spots) and single-cell (22,419 cells) RNA sequencing analyses to explore molecular differences in detail, further validated in vitro through immunohistochemical analysis and patient-derived organoid cultures. RESULTS: We detected specific metabolic alterations and a signature of WNT signalling activation in metastatic cancer cells related to the VCO phenotype. Importantly, in the corresponding healthy liver of CRCLM displaying sprouting angiogenesis, we identified a predominantly expressed capillary subtype of endothelial cells, which could be further explored as a possible predictor for HGP relying on sprouting angiogenesis. CONCLUSION: These findings may prove to be novel therapeutic targets to the treatment of CRCLM, in special the ones relying on VCO.

Rectal Cancer: Open Questions in 2022 Current Standards of Clinical Practice and Ongoing Trials.

BACKGROUND: Rectal cancer remains a complex disease and a relevant global health issue, increasingly affecting also younger patients. This update review summarizes the current standard of care and discusses the individualized treatment approaches taking into consideration individual tumor characteristics and patients preferences. SUMMARY: Remaining "gray zones" of rectal cancer therapy warranting further prospective studies are identified including surgical approaches for rectal cancer, e.g., minimally invasive surgical techniques and lateral lymph node dissection for low rectal cancers. The emerging concept of a watch-and-wait strategy upon clinical complete response after chemoradiotherapy is discussed, also considering the still limited evidence and the clinical challenges arising from individualized patient management. KEY MESSAGES: Finally, currently conducted clinical trials of the German Rectal Cancer Study Group are described, aiming to further individualize multimodal treatment according to risk profiles and strict MRI criteria.

Prognostic value of the micronucleus assay for clinical endpoints in neoadjuvant radiochemotherapy for rectal cancer.

BACKGROUND: The question whether lymphocyte radiosensitivity is representative of patients' response to radiotherapy (RT) remains unsolved. We analyzed lymphocyte cytogenetic damage in patients who were homogeneously treated with preoperative radiochemotherapy (RCT) for rectal cancer within clinical trials. We tested for interindividual variation and consistent radiosensitivity after in-vivo and in-vitro irradiation, analyzed the effect of patients' and RCT characteristics on cytogenetic damage, and tested for correlations with patients' outcome in terms of tumor response, survival and treatment-related toxicity. METHODS: The cytokinesis-block micronucleus cytome (CBMNcyt) assay was performed on the peripheral blood lymphocytes (PBLCs) of 134 patients obtained before, during, at the end of RCT, and during the 2-year follow-up. A subset of PBLCs obtained before RCT was irradiated in-vitro with 3 Gy. RCT included 50.4 Gy of pelvic RT with 5-fluorouracil (5-FU) alone (n = 78) or 5-FU plus oxaliplatin (n = 56). The analyzed variables included patients' age, gender, RT characteristics (planning target volume size [PTV size], RT technique), and chemotherapy characteristics (5-FU plasma levels, addition of oxaliplatin). Outcome was analyzed as tumor regression, patient survival, and acute and late toxicity. RESULTS: Cytogenetic damage increased significantly with the radiation dose and varied substantially between individuals. Women were more sensitive than men; no significant age-dependent differences were observed. There was a significant correlation between the cytogenetic damage after in-vitro irradiation and in-vivo RCT. We found a significant effect of the PTV size on the yields of cytogenetic damage after RCT, while the RT technique had no effect. Neither the addition of oxaliplatin nor the 5-FU levels influenced cytogenetic damage. We found no correlation between patient outcome and the cytogenetic damage. CONCLUSIONS: We found consistent cytogenetic damage in lymphocytes after in-vivo RCT and in-vitro irradiation. Gender was confirmed as a well-known, and the PTV size was identified as a less well-known influencing variable on lymphocyte cytogenetic damage after partial-body irradiation. A consistent level of cytogenetic damage after in-vivo and in-vitro irradiation may indicate the importance of genetic factors for individual radiosensitivity. However, we found no evidence that in-vivo or in-vitro irradiation-induced cytogenetic damage is an adequate biomarker for the response to RCT in rectal cancer patients.

Enhancer of Zeste Homolog 2 in Colorectal Cancer Development and Progression.

BACKGROUND: Colorectal cancer (CRC) is the leading gastrointestinal malignancy. The development from premalignant intraepithelial lesions leading to invasive cancer is paradigmatic for the stepwise carcinogenesis of epithelial cancers, but the knowledge of the underlying mechanism of carcinogenesis and progression of CRC is still incomplete. The understanding of epigenetic mechanisms of carcinogenesis has led to new therapeutic approaches during the last years. Enhancer of zeste homolog 2 (EZH2) is one central epigenetic silencer of the polycomb repressor complex 2 (PRC2) that is already in clinical use as a novel drug target and is associated with poorer prognosis in several cancer entities. PATIENTS AND METHODS: The protein expression of EZH2 and other members of the PRC2 as well as resulting posttranslational modifications were investigated by immunohistochemistry in 187 patients with CRC and in 94 patients with premalignant colorectal lesions and correlated with their clinical outcome. Furthermore, the corresponding mRNA expression levels were analyzed in 217 patients with rectal cancer that were enrolled in a prospective clinical trial. RESULTS: We found a weak expression of EZH2 in normal colon mucosa that increased in low grade, peaked in high grade intraepithelial neoplasia, and decreased again in invasive CRC. The posttranslational modification caused by EZH2 as a measure of EZH2 activity showed the same behavior. Strong protein and mRNA expression of EZH2 were significantly correlated with favorable prognosis in both investigated cohorts. CONCLUSION: The expression and activity of EZH2 are associated with colorectal carcinogenesis and most expressed in intraepithelial high-grade lesions. Strong expression of EZH2 is associated with a significantly favorable prognosis in patients suffering from CRC.

EndoDB: a database of endothelial cell transcriptomics data.

Endothelial cells (ECs) line blood vessels, regulate homeostatic processes (blood flow, immune cell trafficking), but are also involved in many prevalent diseases. The increasing use of high-throughput technologies such as gene expression microarrays and (single cell) RNA sequencing generated a wealth of data on the molecular basis of EC (dys-)function. Extracting biological insight from these datasets is challenging for scientists who are not proficient in bioinformatics. To facilitate the re-use of publicly available EC transcriptomics data, we developed the endothelial database EndoDB, a web-accessible collection of expert curated, quality assured and pre-analyzed data collected from 360 datasets comprising a total of 4741 bulk and 5847 single cell endothelial transcriptomes from six different organisms. Unlike other added-value databases, EndoDB allows to easily retrieve and explore data of specific studies, determine under which conditions genes and pathways of interest are deregulated and assess reprogramming of metabolism via principal component analysis, differential gene expression analysis, gene set enrichment analysis, heatmaps and metabolic and transcription factor analysis, while single cell data are visualized as gene expression color-coded t-SNE plots. Plots and tables in EndoDB are customizable, downloadable and interactive. EndoDB is freely available at https://vibcancer.be/software-tools/endodb, and will be updated to include new studies.

Combined targeting of HER-2 and HER-3 represents a promising therapeutic strategy in colorectal cancer.

BACKGROUND: Abrogation of growth factor-dependent signaling represents an effective therapeutic strategy for patients with colorectal cancer (CRC). Here we evaluated the effectiveness of targeting the epidermal growth factor (EGF) receptors HER-2 and HER-3 in the three cell lines LS513, LS1034 and SW837. METHODS: Treatment with HER-2-specific antibodies trastuzumab and pertuzumab resulted in a mild reduction of cellular viability. In contrast, the antibody-drug conjugate T-DM1 mediated a strong and dose-dependent decrease of viability and Akt phosphorylation. RESULTS: The most striking effects were observed with the dual tyrosine kinase inhibitor lapatinib, and the Pan-ErbB inhibitor afatinib. Selectively, the effect of EGF receptor inhibition was augmented by a combination with 5-fluorouracil and oxaliplatin. Finally, high expression of HER-3 was detected in 121 of 172 locally advanced rectal cancers (70.3%). In conclusion, inhibition of EGF receptors effectively blocks downstream signaling and significantly impairs viability of CRC cells. However, the effectiveness of receptor inhibition highly depends on the inhibitors' mode of action, as targeting HER-2 alone is not sufficient. CONCLUSION: Since HER-2 and HER-3 are expressed in a relevant number of patients, targeting both receptors may represent a promising therapeutic strategy for CRC.

Manipulating Angiogenesis by Targeting Endothelial Metabolism: Hitting the Engine Rather than the Drivers-A New Perspective?

Excessive angiogenesis (i.e., the formation of new blood vessels) contributes to different pathologies, among them cancer and ocular disorders. Conversely, dysfunction of endothelial cells (ECs) contributes to cardiovascular complications, as is the case in diabetes. Inhibition of pathologic angiogenesis in blinding eye disease and cancer by targeting growth factors such as vascular endothelial growth factor has become an accepted therapeutic strategy. However, recent studies also unveiled the emerging importance of EC metabolism in controlling angiogenesis. In this overview, we will discuss recent insights in the metabolic regulation of angiogenesis, focusing on the best-characterized metabolic pathways, and highlight deregulation of EC metabolism in cancer and diabetes. We will give an outlook on how targeting EC metabolism can be used for blocking pathologic angiogenesis and for normalizing EC dysfunction.

Central Role of Metabolism in Endothelial Cell Function and Vascular Disease.

The importance of endothelial cell (EC) metabolism and its regulatory role in the angiogenic behavior of ECs during vessel formation and in the function of different EC subtypes determined by different vascular beds has been recognized only in the last few years. Even more importantly, apart from a role of nitric oxide and reactive oxygen species in EC dysfunction, deregulations of EC metabolism in disease only recently received increasing attention. Although comprehensive metabolic characterization of ECs still needs further investigation, the concept of targeting EC metabolism to treat vascular disease is emerging. In this overview, we summarize EC-specific metabolic pathways, describe the current knowledge on their deregulation in vascular diseases, and give an outlook on how vascular endothelial metabolism can serve as a target to normalize deregulated endothelium.

Repeated adjuvant anti-CEA radioimmunotherapy after resection of colorectal liver metastases: Safety, feasibility, and long-term efficacy results of a prospective phase 2 study.

BACKGROUND: In previous work, a single administration of anticarcinoembryonic antigen (anti-CEA) 131 I-labetuzumab radioimmunotherapy (RIT) after complete resection of colorectal liver metastases was well tolerated and significantly improved survival compared with controls. In the current phase 2 trial, the authors studied repeated RIT in the same setting, examining safety, feasibility, and efficacy. METHODS: Sixty-three patients (median age, 64.5 years) received RIT at 40 to 50 millicuries/m2 per dose. Before the receipt of RIT, restaging was performed with computed tomography/magnetic resonance imaging and 18 F-fluorodeoxyglucose-positron emission to confirm that patients were "truly adjuvant." Patients who had elevated serum CEA levels or radiographically inconclusive new lesions were classified as "possibly nonadjuvant," but they also received RIT. Time to progression (TTP), overall survival (OS), and cause-specific survival (CSS) were calculated. The median follow-up was 54 months. RESULTS: After the first course of RIT, 14 of 63 patients experienced National Cancer Institute Common Toxicity Criteria grade 4 hematotoxicity; 19 patients did not receive the second course of RIT because of impaired performance status (N = 5) or relapse (N = 14). After the second course of RIT, 9 of 44 patients experienced National Cancer Institute Common Toxicity Criteria grade 4 hematotoxicity. Five patients developed myelodysplastic syndrome (MDS) from 22 to 55 months after their last RIT. The median TTP, OS, and CSS for all patients were 16, 55, and 60 months, respectively. The "truly adjuvant" patients (N = 39) had an improved median TTP (not reached vs 6.1 months; hazard ratio, 0.12; P < .001), OS (75.6 vs 33.4 months; hazard ratio, 0.44; P = .014), and CSS (not reached vs 41.4 months; hazard ratio,0.42; P = .014) compared with "possibly nonadjuvant" patients (N = 24). CONCLUSIONS: Repeated RIT with 131 I-labetuzumab is feasible but is associated with hematotoxicity. Survival is very encouraging, especially for "truly adjuvant" patients. However, the maximum safe dose of 131 I-labetuzumab is a single administration of 50 millicuries/m2 . Cancer 2017;123:638-649. © 2016 American Cancer Society.

Tumor vessel disintegration by maximum tolerable PFKFB3 blockade.

Blockade of the glycolytic activator PFKFB3 in cancer cells (using a maximum tolerable dose of 70 mg/kg of the PFKFB3 blocker 3PO) inhibits tumor growth in preclinical models and is currently being tested as a novel anticancer treatment in phase I clinical trials. However, a detailed preclinical analysis of the effects of such maximum tolerable dose of a PFKFB3 blocker on the tumor vasculature is lacking, even though tumor endothelial cells are hyper-glycolytic. We report here that a high dose of 3PO (70 mg/kg), which inhibits cancer cell proliferation and reduces primary tumor growth, causes tumor vessel disintegration, suppresses endothelial cell growth for protracted periods, (model-dependently) aggravates tumor hypoxia, and compromises vascular barrier integrity, thereby rendering tumor vessels more leaky and facilitating cancer cell intravasation and dissemination. These findings contrast to the effects of a low dose of 3PO (25 mg/kg), which induces tumor vessel normalization, characterized by vascular barrier tightening and maturation, but reduces cancer cell intravasation and metastasis. Our findings highlight the importance of adequately dosing a glycolytic inhibitor for anticancer treatment.

The utilization of multidisciplinary tumor boards (MDT) in clinical routine: results of a health care research study focusing on patients with metastasized colorectal cancer.

PURPOSE: Multidisciplinary tumor boards (MDT) have been advocated as standard of care in modern oncology. German guidelines for metastasized colorectal cancer (mCRC) recommend MDT discussion of colon cancer patients after completion of primary tumor therapy but stage IV colon cancer as well as rectal cancer patients prior to any therapy. In this health care research study, we evaluated application and decisional consequences of this approach in clinical routine. METHODS: All major institutions providing oncological care in southern Lower Saxony and Northern Hesse (N = 11) were invited. Patients with mCRC diagnosed between 01/2011 and 12/2013 were eligible. Data were collected using a standardized patient report form and stored in a GCP-conform EDC-system (secuTrial®). RESULTS: A university medical center, four teaching hospitals, one communal hospital, and three oncological focus practices participated in the study. In total, 470 patients with a median age of 70 years were enrolled. Guideline conform MDT discussion was performed in 63% of operated colon cancer patients, 38% of stage IV colon cancer patients and 47% of rectal cancer patients, respectively. Resection of metastases was performed in 41% of cases. Patients ≥70 years (n = 250) received significantly more often treatment following MDT discussion (86 versus 64%, p = 0.0002). Not the resection rate (48 versus 57%, p = 0.1574) but indication for preoperative chemotherapy (57 versus 33%, p = 0.0056) significantly differed when patients with single organ metastases experienced MDT discussion. CONCLUSIONS: MDT discussion is not as established as advocated by national guidelines. Treatment decisions differ especially in older patients and those with single organ metastases.

Stage-Dependent Frequency of Lymph Node Metastases in Patients With Rectal Carcinoma After Preoperative Chemoradiation: Results from the CAO/ARO/AIO-94 Trial and From a Comparative Prospective Evaluation With Extensive Pathological Workup.

BACKGROUND: For patients with ycT1/2 rectal carcinomas after neoadjuvant chemoradiotherapy, local excision instead of radical surgery has increasingly been discussed as a way to avoid postoperative morbidity associated with radical surgery. OBJECTIVE: The purpose of this study was to determine the incidence of lymph node metastases in total mesorectal excision specimens with ypT0, ypT1/2, and ypT3/4 rectal cancers. DESIGN: This is a prospective and retrospective cohort study. SETTINGS: This study was conducted in tertiary referral hospitals that are part of the German Rectal Cancer Study Group. PATIENTS: A total of 479 patients with stage II and III rectal cancers treated within phase III trials of the German Rectal Cancer Study Group were evaluated. Specimens from 81 patients treated in the Working Group of Surgical Oncology/Working Group of Radiation Oncology/Working Group of Medical Oncology of the Germany Cancer Society (CAO/ARO/AIO-04) trial were prospectively studied with extensive microscopic screening of the entire mesorectum. The frequency and localization of nodal metastases were specified and compared with those of 398 patients having received neoadjuvant chemoradiation within the CAO/ARO/AIO-94 trial. MAIN OUTCOME MEASURES: Frequency and localization of mesorectal lymph node metastases in patients with ypT0, ypT1/2, or ypT3/4 cancer were measured. RESULTS: A mean number of 28.0 ± 13.7 nodes were detected per specimen within the prospective group. A total of 25% of patients in the ypT1/2 group had nodal metastases compared with 40% in the ypT3/4 group. Patients with node-positive ypT1/2 had a mean number of 2.2 metastases, and 55% of these metastases were located far from the primary lesion in the proximal mesorectum. Within the CAO/ARO/AIO-94 cohort (n = 398), 19% of patients with ypT1/2 (ypT1 = 22%; ypT2 = 18%) had ypN+ status compared with 43% with ypT3/4 cancers (ypT3 = 40%; ypT4 = 73%). LIMITATIONS: Low numbers of patients with ypT0 limited the evaluation of nodal metastases in pathologic complete responders. CONCLUSIONS: Even in good responders (ypT1/2), >20% of rectal carcinomas still harbored residual lymph node metastases. Local excision for patients with ycT1/2 rectal cancers would, thus, miss metastases in a considerable percentage and might involve the risk of significant undertreatment in a number of patients.

Reduced toxicity in the treatment of locally advanced rectal cancer: a comparison of volumetric modulated arc therapy and 3D conformal radiotherapy.

BACKGROUND: Excellent dosimetric characteristics were demonstrated for volumetric modulated arc therapy (VMAT) in preoperative chemoradiotherapy (CRT) for locally advanced rectal cancer (LARC). In a single-center retrospective analysis, we tested whether these advantages may translate into significant clinical benefits. We compared VMAT to conventional 3D conformal radiotherapy (3DCRT) in patients, homogeneously treated according to the control arm of the CAO/ARO/AIO-04 trial. METHODS: CRT consisted of pelvic irradiation with 50.4/1.8Gy by VMAT (n = 81) or 3DCRT (n = 107) and two cycles of 5-fluorouracil. Standardized total mesorectal excision surgery was performed within 4-6 weeks. The tumor regression grading (TRG) was assessed by the Dworak score. Acute and late toxicity were evaluated via the Common Terminology Criteria for Adverse Events and the Late effects of normal tissues scale, respectively. Side effects greater than or equal to grade 3 were considered high-grade. RESULTS: Median follow-up was 18.3 months in the VMAT group and 61.5 months in the 3DCRT group with no differences in TRG between them (p = 0.1727). VMAT treatment substantially reduced high-grade acute and late toxicity, with 5 % versus 20 % (p = 0.0081) and 6 % vs. 22 % (p = 0.0039), respectively. With regard to specific organs, differences were found in skin reaction (p = 0.019) and proctitis (p = 0.0153). CONCLUSIONS: VMAT treatment in preoperative CRT for LARC showed the potential to substantially reduce high-grade acute and late toxicity. Importantly, we could demonstrate that VMAT irradiation did not impair short-term oncological results. We conclude, that the reduced toxicity after VMAT irradiation may pave the way for more efficient systemic therapies, and hopefully improved patient survival in the multimodal treatment of LARC.

Enhancement of colorectal cancer therapy through interruption of the HSF1-HSP90 axis by p53 activation or cell cycle inhibition.

The stress-associated molecular chaperone system is an actionable target in cancer therapies. It is ubiquitously upregulated in cancer tissues and enables tumorigenicity by stabilizing hundreds of oncoproteins and disturbing the stoichiometry of protein complexes. Most inhibitors target the key component heat-shock protein 90 (HSP90). However, although classical HSP90 inhibitors are highly tumor-selective, they fail in phase 3 clinical oncology trials. These failures are at least partly due to an interference with a negative feedback loop by HSP90 inhibition, known as heat-shock response (HSR): in response to HSP90 inhibition there is compensatory synthesis of stress-inducible chaperones, mediated by the transcription factor heat-shock factor 1 (HSF1). We recently identified that wildtype p53 (p53) actively reduces the HSR by repressing HSF1 via a p21-CDK4/6-MAPK-HSF1 axis. Here we test the hypothesis that in HSP90-based therapies simultaneous p53 activation or direct cell cycle inhibition interrupts the deleterious HSF1-HSR axis and improves the efficiency of HSP90 inhibitors. Indeed, we find that the clinically relevant p53 activator Idasanutlin suppresses the HSF1-HSR activity in HSP90 inhibitor-based therapies. This combination synergistically reduces cell viability and accelerates cell death in p53-proficient colorectal cancer (CRC) cells, murine tumor-derived organoids and patient-derived organoids (PDOs). Mechanistically, upon combination therapy human CRC cells strongly upregulate p53-associated pathways, apoptosis, and inflammatory immune pathways. Likewise, in the chemical AOM/DSS CRC model in mice, dual HSF1-HSP90 inhibition strongly represses tumor growth and remodels immune cell composition, yet displays only minor toxicities in mice and normal mucosa-derived organoids. Importantly, inhibition of the cyclin dependent kinases 4 and 6 (CDK4/6) under HSP90 inhibition phenocopies synergistic repression of the HSR in p53-proficient CRC cells. Even more important, in p53-deficient (mutp53-harboring) CRC cells, an HSP90 inhibition in combination with CDK4/6 inhibitors similarly suppresses the HSF1-HSR system and reduces cancer growth. Likewise, p53-mutated PDOs strongly respond to dual HSF1-HSP90 pathway inhibition and thus, providing a strategy to target CRC independent of the p53 status. In sum, activating p53 (in p53-proficient cancer cells) or inhibiting CDK4/6 (independent of the p53 status) provide new options to improve the clinical outcome of HSP90-based therapies and to enhance colorectal cancer therapy.

OrganoIDNet: a deep learning tool for identification of therapeutic effects in PDAC organoid-PBMC co-cultures from time-resolved imaging data.

PURPOSE: Pancreatic Ductal Adenocarcinoma (PDAC) remains a challenging disease due to its complex biology and aggressive behavior with an urgent need for efficient therapeutic strategies. To assess therapy response, pre-clinical PDAC organoid-based models in combination with accurate real-time monitoring are required. METHODS: We established stable live-imaging organoid/peripheral blood mononuclear cells (PBMCs) co-cultures and introduced OrganoIDNet, a deep-learning-based algorithm, capable of analyzing bright-field images of murine and human patient-derived PDAC organoids acquired with live-cell imaging. We investigated the response to the chemotherapy gemcitabine in PDAC organoids and the PD-L1 inhibitor Atezolizumab, cultured with or without HLA-matched PBMCs over time. Results obtained with OrganoIDNet were validated with the endpoint proliferation assay CellTiter-Glo. RESULTS: Live cell imaging in combination with OrganoIDNet accurately detected size-specific drug responses of organoids to gemcitabine over time, showing that large organoids were more prone to cytotoxic effects. This approach also allowed distinguishing between healthy and unhealthy status and measuring eccentricity as organoids' reaction to therapy. Furthermore, imaging of a new organoids/PBMCs sandwich-based co-culture enabled longitudinal analysis of organoid responses to Atezolizumab, showing an increased potency of PBMCs tumor-killing in an organoid-individual manner when Atezolizumab was added. CONCLUSION: Optimized PDAC organoid imaging analyzed by OrganoIDNet represents a platform capable of accurately detecting organoid responses to standard PDAC chemotherapy over time. Moreover, organoid/immune cell co-cultures allow monitoring of organoid responses to immunotherapy, offering dynamic insights into treatment behavior within a co-culture setting with PBMCs. This setup holds promise for real-time assessment of immunotherapeutic effects in individual patient-derived PDAC organoids.

Spontaneous metastasis xenograft models link CD44 isoform 4 to angiogenesis, hypoxia, EMT and mitochondria-related pathways in colorectal cancer.

Hematogenous metastasis limits the survival of colorectal cancer (CRC) patients. Here, we illuminated the roles of CD44 isoforms in this process. Isoforms 3 and 4 were predominantly expressed in CRC patients. CD44 isoform 4 indicated poor outcome and correlated with epithelial-mesenchymal transition (EMT) and decreased oxidative phosphorylation (OxPhos) in patients; opposite associations were found for isoform 3. Pan-CD44 knockdown (kd) independently impaired primary tumor formation and abrogated distant metastasis in CRC xenografts. The xenograft tumors mainly expressed the clinically relevant CD44 isoforms 3 and 4. Both isoforms were enhanced in the paranecrotic, hypoxic tumor regions but were generally absent in lung metastases. Upon CD44 kd, tumor angiogenesis was increased in the paranecrotic areas, accompanied by reduced hypoxia-inducible factor-1α and CEACAM5 but increased E-cadherin expression. Mitochondrial genes and proteins were induced upon pan-CD44 kd, as were OxPhos genes. Hypoxia increased VEGF release from tumor spheres, particularly upon CD44 kd. Genes affected upon CD44 kd in xenografts specifically overlapped concordantly with genes correlating with CD44 isoform 4 (but not isoform 3) in patients, validating the clinical relevance of the used model and highlighting the metastasis-promoting role of CD44 isoform 4.

Enrichment of CD133-expressing cells in rectal cancers treated with preoperative radiochemotherapy is an independent marker for metastasis and survival.

BACKGROUND: The transmembrane glycoprotein CD133 (cluster of differentiation 133; also known as Prominin or PROM1) has been described as a potential stem cell marker in colorectal cancer and is associated with higher tumorigenic potential and resistance to radiochemotherapy (RCT). In this study, CD133 expression was evaluated in pre-RCT tumor biopsies and the corresponding post-RCT surgical specimens from patients with locally advanced rectal adenocarcinoma, and expression levels were correlated with histopathologic features and clinical follow-up. METHODS: One hundred twenty-six patients with International Union Against Cancer (UICC) stage II/III rectal cancer who received preoperative 5-fluorouracil (5-FU)-based RCT within the German Rectal Cancer Trials were investigated. Pre-RCT and post-RCT CD133 expression levels were determined using immunohistochemistry and were correlated with histopathologic parameters, tumor regression grade, cancer recurrence, and patient survival. RESULTS: Compared with pre-RCT biopsies, significantly higher CD133 expression was observed in tumor specimens (P = .01). However, no correlations were observed for either biopsies or tumor specimens between CD133 expression levels, histopathologic characteristics, or survival. In matched analyses of corresponding biopsy/tumor pairs, patients who had an increased fraction of CD133-expressing (CD133+) cells after preoperative RCT had significantly higher residual tumor stages (P = .02) and lower histopathologic tumor regression (P < .01). Moreover, these patients had significantly reduced disease-free survival and cancer-specific overall survival in univariate analysis (P < .001 and P = .004, respectively) and multivariate analysis (P = .003 and P = .024, respectively). CONCLUSIONS: The enrichment of CD133+ cancer cells during preoperative RCT was correlated with minor local tumor response, increased distant cancer recurrence, and decreased survival. The current results indicate that the up-regulation of intratumoral CD133 expression, in contrast to absolute pre-RCT and post-RCT CD133 levels, plays an important role in tumor progression and metastasis in patients with rectal cancer who are receiving neoadjuvant RCT.

CDK4/6 inhibition confers protection of normal gut epithelia against gemcitabine and the active metabolite of irinotecan.

Cancer chemotherapy relies on a high ratio of toxicity toward cancer cells vs. nonmalignant cells, making it desirable to protect normal cells. Among the nonmalignant cells, epithelia of the gut belong to the most vulnerable ones toward chemotherapeutics. Here, we use a murine intestinal organoid model to assess a strategy for protecting such epithelia against chemotherapy. Cell cycle progression was first stalled by palbociclib, a clinically established cyclin-dependent kinase 4/6 (CDK4/6) inhibitor. Washout of the drug allowed subsequent outgrowth of gut organoids. This transient cell cycle arrest conferred near-complete protection of the cells toward the nucleoside analogue gemcitabine. Moreover, pre-treatment with palbociclib protected the organoids against SN-38, the topoisomerase I-inhibiting metabolite of irinotecan, which is otherwise known for its severe gastrointestinal toxicities. In contrast, RB1-mutated cancer cells were not protected against gemcitabine or SN-38 when pre-treated with palbociclib. Taken together, these results outline a strategy for protecting nonmalignant cells against the toxicities of chemotherapeutics commonly used to treat advanced colorectal and pancreatic cancer. We propose that this strategy is particularly promising to protect the gut when treating RB1-deficient tumors that fail to arrest the cell cycle in response to CDK4/6 inhibitors. [Figure: see text].

Implications of Rectal Cancer Radiotherapy on the Immune Microenvironment: Allies and Foes to Therapy Resistance and Patients' Outcome.

Aside from surgical resection, locally advanced rectal cancer is regularly treated with neoadjuvant chemoradiotherapy. Since the concept of cancer treatment has shifted from only focusing on tumor cells as drivers of disease progression towards a broader understanding including the dynamic tumor microenvironment (TME), the impact of radiotherapy on the TME and specifically the tumor immune microenvironment (TIME) is increasingly recognized. Both promoting as well as suppressing effects on anti-tumor immunity have been reported in response to rectal cancer (chemo-)radiotherapy and various targets for combination therapies are under investigation. A literature review was conducted searching the PubMed database for evidence regarding the pleiotropic effects of (chemo-)radiotherapy on the rectal cancer TIME, including alterations in cytokine levels, immune cell populations and activity as well as changes in immune checkpoint proteins. Radiotherapy can induce immune-stimulating and -suppressive alterations, potentially mediating radioresistance. The response is influenced by treatment modalities, including the dosage administered and the highly individual intrinsic pre-treatment immune status. Directly addressing the main immune cells of the TME, this review aims to highlight therapeutical implications since efficient rectal cancer treatment relies on personalized strategies combining conventional therapies with immune-modulating approaches, such as immune checkpoint inhibitors.