Epistemology of the Origin of Cancer II: Fibroblasts Are the First Cells to Undergo Neoplastic Transformation.

BACKGROUND/AIMS: Many questions in cancer biology remain unanswered. Perhaps the most important issues remaining to be addressed focus on the molecular basis of carcinogenesis. Today's cancer focus lies on genetics and gene expression, which is unlikely to explain the true cause of most cancers or lead to a cure. METHODS: Earlier, we provided a plausible mechanism for this process, specifically, that most cancers develop in response to pathogenic stimuli that induce chronic inflammation, fibrosis, and remodeling of the cellular microenvironment. Collectively, these changes generate a precancerous niche (PCN) in which fibrosis and remodeling are ongoing secondary to persistent inflammation, followed by the deployment of a chronic stress escape strategy (CSES). If the CSES is unsuccessful, the cell undergoes a normal cell to cancer cell transformation (NCCT). RESULTS: Here, we highlight the critical role of fibroblasts as the first cells to undergo neoplastic transformation to a cancerous phenotype which is based on several critical findings. First, persistent disruption of homeostatic crosstalk increases lysyl oxidase activity and lysine oxidation which leads to increased collagen stiffness and decreased elasticity. If unresolved, chronic tissue stress will lead to an escape strategy that involves the recruitment of fibroblasts and fibrocytes from the bone marrow as well as cells undergoing an epithelial-mesenchymal transition (EMT). This yields a heterogeneous pool of cells that express both epithelial and mesenchymal markers and that will ultimately differentiate into cancer-associated fibroblasts (CAFs). Finally, CAFs undergo a mesenchymalepithelial transition (MET) and express epithelial markers that facilitate their integration into the target tissue. CONCLUSION: Here, we review the published findings that led us to this conclusion which is the most plausible answer to this critical question.

Physics Essentials Enable Deeper Understanding in Signaling and Crosstalk of the Carcinogenesis Paradigm "Epistemology of the Origin of Cancer".

Radioactivity and radiation-induced mutations are believed to be primary causal examples of cancer-initiating events (stimulus). The assumption that an increase in cancer risk develops from any amount of radiation gave rise to the linear no-threshold model. This also led to the assumption that cancer is caused by somatic mutations as described by the somatic mutation theory. Against this backdrop, in actuality only ~5%-10% of cancers result from somatic mutations or its various modifications, while ~80% of cancers are still termed as 'sporadic', meaning that their cause is unknown. Therefore, both the linear no-threshold model and the somatic mutation theory have resulted in an incongruity in thinking. Decades of molecular and clinical research since 2012 led to the development of the cancer paradigm, "Epistemology of the origin of cancer", which explains why the majority of cancers originate as a result of a sixstep sequence of events. An understanding of the essentials of physics helps to explain the interconnections between physics and the biology of cancer. This allows for a much-needed reconciliation of past errors and leads to a deeper understanding of carcinogenesis.

Somatic Mutation Theory - Why it's Wrong for Most Cancers.

Hysteron proteron reverses both temporal and logical order and this syllogism occurs in carcinogenesis and the somatic mutation theory (SMT): the first (somatic mutation) occurs only after the second (onset of cancer) and, therefore, observed somatic mutations in most cancers appear well after the early cues of carcinogenesis are in place. It is no accident that mutations are increasingly being questioned as the causal event in the origin of the vast majority of cancers as clinical data show little support for this theory when compared against the metrics of patient outcomes. Ever since the discovery of the double helical structure of DNA, virtually all chronic diseases came to be viewed as causally linked to one degree or another to mutations, even though we now know that genes are not simply blueprints, but rather an assemblage of alphabets that can, under non-genetic influences, be used to assemble a business letter or a work of Shakespearean literature. A minority of all cancers is indeed caused by mutations but the SMT has been applied to all cancers, and even to chemical carcinogenesis, in the absence of hard evidence of causality. Herein, we review the 100 year story of SMT and aspects that show why genes are not just blueprints, how radiation and mutation are associated in a more nuanced view, the proposed risk of cancer and bad luck, and the in vitro and in vivo evidence for a new cancer paradigm. This paradigm is scientifically applicable for the majority of non-heritable cancers and consists of a six-step sequence for the origin of cancer. This new cancer paradigm proclaims that somatic mutations are epiphenomena or later events occurring after carcinogenesis is already underway. This serves not just as a plausible alternative to SMT and explains the origin of the majority of cancers, but also provides opportunities for early interventions and prevention of the onset of cancer as a disease.

Cell-cell communication in the tumor microenvironment, carcinogenesis, and anticancer treatment.

The delineation of key molecular pathways has enhanced our knowledge of the biology of tumor microenvironment, tumor dissemination, and carcinogenesis. The complexities of cell-cell communication and the possibilities for modulation provide new opportunities for treating cancers. Cells communicate by direct and indirect signaling. Direct cell-cell communication involves both, self-self-communication (intracrine and autocrine), and adjacent communication with nearby cells (juxtacrine), which themselves are regulated by distinct pathways. Indirect intercellular communication involves local communication over short distances (paracrine and synaptic signaling) or over large distances via hormones (endocrine). The essential components of cell-cell communication involve communication junctions (Connexins, Plasmodesmata, Ion Channels, Chemical Synapses, and Pannexins), occluding junctions (Tight Junctions), and anchoring junctions (Adherens, Desmosomes, Focal Adhesions, and Hemidesmosomes). The communication pathways pass through junctions at physical cell-cell attachments, and they go, as well, through the extracellular matrix (ECM) via the different transmembrane adhesion proteins (Cadherins and Integrins). We have here reviewed cell-cell communication involving (1) the components of junctions and their dynamic interplay with the other aspects of communication, including (2) the tumor microenvironment and carcinogenesis, (3) coupling and migration, (4) the underlying cell-cell and sub-cellular communication mechanisms (signaling) of anticancer treatments, and finally, (5) aspects of recent research on cell-cell communication.

Undervalued criteria in the evaluation of multimodal trials for upper GI cancers.

Global economies and their health systems face a huge challenge from cancer: 1 in 3 women and 1 in 2 men will develop cancer in their lifetime. In the less developed countries, the volume of cancer patients will overwhelm the existing healthcare systems. Even in developed regions, patients with upper gastrointestinal (GI) cancer usually present with locally advanced tumors that their prognosis is poor. A detailed knowledge of anatomy, embryology, epidemiology, tumor classifications and tumor growth is key understanding and evaluating the relevant research. We review undervalued criteria necessary to evaluate the response to multimodal therapy for upper GI cancers.

Epistemology of the origin of cancer: a new paradigm.

BACKGROUND: Carcinogenesis is widely thought to originate from somatic mutations and an inhibition of growth suppressors, followed by cell proliferation, tissue invasion, and risk of metastasis. Fewer than 10% of all cancers are hereditary; the ratio in gastric (1%), colorectal (3-5%) and breast (8%) cancers is even less. Cancers caused by infection are thought to constitute some 15% of the non-hereditary cancers. Those remaining, 70 to 80%, are called "sporadic," because they are essentially of unknown etiology. We propose a new paradigm for the origin of the majority of cancers. PRESENTATION OF HYPOTHESIS: Our paradigm postulates that cancer originates following a sequence of events that include (1) a pathogenic stimulus (biological or chemical) followed by (2) chronic inflammation, from which develops (3) fibrosis with associated changes in the cellular microenvironment. From these changes a (4) pre-cancerous niche develops, which triggers the deployment of (5) a chronic stress escape strategy, and when this fails to resolve, (6) a transition of a normal cell to a cancer cell occurs. If we are correct, this paradigm would suggest that the majority of the findings in cancer genetics so far reported are either late events or are epiphenomena that occur after the appearance of the pre-cancerous niche. TESTING THE HYPOTHESIS: If, based on experimental and clinical findings presented here, this hypothesis is plausible, then the majority of findings in the genetics of cancer so far reported in the literature are late events or epiphenomena that could have occurred after the development of a PCN. Our model would make clear the need to establish preventive measures long before a cancer becomes clinically apparent. Future research should focus on the intermediate steps of our proposed sequence of events, which will enhance our understanding of the nature of carcinogenesis. Findings on inflammation and fibrosis would be given their warranted importance, with research in anticancer therapies focusing on suppressing the PCN state with very early intervention to detect and quantify any subclinical inflammatory change and to treat all levels of chronic inflammation and prevent fibrotic changes, and so avoid the transition from a normal cell to a cancer cell. IMPLICATION OF THE HYPOTHESIS: The paradigm proposed here, if proven, spells out a sequence of steps, one or more of which could be interdicted or modulated early in carcinogenesis to prevent or, at a minimum, slow down the progression of many cancers.

Imagine a world without cancer.

BACKGROUND: Since the "War on Cancer" was declared in 1971, the United States alone has expended some $300 billion on research, with a heavy focus on the role of genomics in anticancer therapy. Voluminous data have been collected and analyzed. However, in hindsight, any achievements made have not been realized in clinical practice in terms of overall survival or quality of life extended. This might be justified because cancer is not one disease but a conglomeration of multiple diseases, with widespread heterogeneity even within a single tumor type. DISCUSSION: Only a few types of cancer have been described that are associated with one major signaling pathway. This enabled the initial successful deployment of targeted therapy for such cancers. However, soon after this targeted approach was initiated, it was subverted as cancer cells learned and reacted to the initial treatments, oftentimes rendering the treatment less effective or even completely ineffective. During the past 30 plus years, the cancer classification used had, as its primary aim, the facilitation of communication and the exchange of information amongst those caring for cancer patients with the end goal of establishing a standardized approach for the diagnosis and treatment of cancers. This approach should be modified based on the recent research to affect a change from a service-based to an outcome-based approach. The vision of achieving long-term control and/or eradicating or curing cancer is far from being realized, but not impossible. In order to meet the challenges in getting there, any newly proposed anticancer strategy must integrate a personalized treatment outcome approach. This concept is predicated on tumor- and patient-associated variables, combined with an individualized response assessment strategy for therapy modification as suggested by the patient's own results. As combined strategies may be outcome-orientated and integrate tumor-, patient- as well as cancer-preventive variables, this approach is likely to result in an optimized anticancer strategy. SUMMARY: Herein, we introduce such an anticancer strategy for all cancer patients, experts, and organizations: Imagine a World without Cancer.

Intraperitoneal chemotherapy and its evolving role in management of gastric cancer with peritoneal metastases.

Advanced gastric cancer (GC) has been recognized as lethal disease when peritoneal metastases (PM) occurred. There is no standard treatment for advanced GC with PM. Until 1980s, the therapeutic arena for these patients had remained stagnant, with no therapeutic approach having shown a survival gain in GC with PM. However, cytoreductive surgery (CRS) with peritonectomy procedures and intraperitoneal chemotherapy (IPC) promising new combined therapeutic approach to achieve disease control for GC with PM. The recent publications changed the GC with PM treatment landscape by providing an evidence that CRS and IPC led to prolongation in overall survival (OS). This review will provide an overview of the evolving role of CRS and IPC in the management of advanced GC with PM in the current era.

Reversibility in male idiopathic osteoporosis possible.

Summary: A 44-year-old athletic man presented in 2009 with severe low back pain. Dual-energy x-ray absorptiometry revealed severe osteoporosis; serum testosterone was 189 ng/dL while serum estradiol (E2) measured by liquid chromatography/mass spectrometry was 8 pg/mL. DNA was extracted and sequenced from a blood sample from the patient since his maternal first cousin also had low bone mass and both patients were screened for aromatase dysfunction by PCR analysis for the CYP19A1 gene, which encodes aromatase. No known pathologic mutations were observed in the coding exons, but novel single nucleotide polymorphisms were detected both in the proband and in his cousin. Treatment with topical testosterone started in August 2010. Over the next 8 years, testosterone dosage was varied and switched from topical gel to injections and maintained on depo-injections of testosterone at about 60 mg once per week. Re-examination in March 2012 included a brain MRI to exclude pituitary lesions; hyperparathyroidism was ruled out (normal serum parathyroid hormone, calcium, and calcium to phosphorous ratio) and celiac disease was excluded (negative transglutaminase antibodies). Follow-up in October 2018 showed improved bone mineral density of the lumbar spine by 29% and of the left femoral hip by 15% compared to baseline measurements. This reveals the importance of measuring serum E2 for making the correct diagnosis, as well as for monitoring a therapeutic effect. Herein, we propose treatment of male osteoporosis where serum E2 levels are below about 20 pg/mL with testosterone to reverse osteoporosis. Learning points: Estrogen deficiency in the diagnosis of male idiopathic osteoporosis. Importance of serum estradiol in male osteoporosis. Role of polymorphisms in aromatase gene on bone health. Reversal of osteoporosis. Tailored testosterone treatment for bone health.

Peritoneal carcinomatosis: cytoreductive surgery and HIPEC--overview and basics.

Tumor involvement of the peritoneum-peritoneal carcinomatosis-is a heterogeneous form of cancer that had been generally regarded as a sign of systemic tumor disease and as a terminal condition. The multimodal treatment approach for patients with peritoneal carcinomatosis, which had been conceived and developed, consists of what is known as cytoreductive surgery, followed by hyperthermic intraperitoneal chemotherapy (HIPEC). Depending on the tumor mass as assessed intraoperatively and the histopathological differentiation, patients who undergo cytoreductive surgery and HIPEC have a significant survival benefit. Mean increases in the survival period ranging from six months to up to four years have now been reported. In view of the substantial logistic effort and the extent of the surgery involved, this treatment approach represents a major challenge both for patients and for surgical oncologists, as well as for the members of the overall interdisciplinary structure required, which includes oncology, anesthesiology and intensive care, psycho-oncology, and patient management. The surgical procedures alone may take 8-14 hr. The present paper provides an overview of the basis for the approach and the use of specialized classifications and quantitative prognostic indicators.

Tumor suppressor gene adenomatous polyposis coli downregulates intestinal transport.

Loss of function mutations of the tumor suppressor gene adenomatous polyposis coli (APC) underly the familial adenomatous polyposis. Mice carrying an inactivating mutation in the apc gene (apc (Min/+)) similarly develop intestinal polyposis. APC is effective at least in part by degrading ß-catenin and lack of APC leads to markedly enhanced cellular ß-catenin levels. ß-Catenin has most recently been shown to upregulate the Na+/K+ ATPase. The present study, thus, explored the possibility that APC could influence intestinal transport. The abundance and localization of ß-catenin were determined utilizing Western blotting and confocal microscopy, the activity of the electrogenic glucose carrier (SGLT1) was estimated from the glucose-induced current in jejunal segments utilizing Ussing chamber experiments and the Na+/H+ exchanger (NHE3) activity from Na+ -dependent re-alkalinization of cytosolic pH (ΔpH(i)) following an ammonium pulse employing BCECF fluorescence. As a result, ß-catenin abundance in intestinal tissue was significantly higher in apc (Min/+) mice than in wild-type mice (apc (+/+)). The ß-catenin protein was localized in the basolateral membrane. Both, the glucose-induced current and ΔpH(i) were significantly higher in apc (Min/+) mice than in apc (+/+) mice. In conclusion, intestinal electrogenic transport of glucose and intestinal Na+/H+ exchanger activity are both significantly enhanced in apc (Min/+) mice, pointing to a role of APC in the regulation of epithelial transport.

Cytoreductive surgery and HIPEC in peritoneal recurrent ovarian cancer: experience and lessons learned.

PURPOSE: Peritoneal recurrence of ovarian cancer is frequent after primary surgery and chemotherapy and has poor long-term survival. De novo cytoreductive surgery is crucial with the potential to improve prognosis, especially when combined with hyperthermic intraperitoneal chemotherapy (HIPEC). METHODS: The sampled data of 40 consecutive patients were retrospectively analyzed. Thirty-one patients were treated with cytoreductive surgery combined with hyperthermic intraperitoneal chemotherapy. RESULTS: No patient was lost in the perioperative period, and the combined procedure was performed with acceptable morbidity. Colon-preserving cytoreductive surgery was associated with reduced morbidity. CONCLUSIONS: Patients suffering from peritoneal recurrence of ovarian cancer should be considered for radical reoperation with HIPEC in a center with expertise in multimodal therapeutic options. Organ-preserving cytoreductive surgery allows complete cytoreduction with the goal of decreasing morbidity.

Phosphoglycerate kinase 1 a promoting enzyme for peritoneal dissemination in gastric cancer.

Peritoneal carcinomatosis is a frequent finding in gastric cancer associated with a poor prognosis. The features that enable gastric tumors to disseminate are poorly understood until now. Previously, we showed elevated mRNA levels of phosphoglycerate kinase 1 (PGK1), an adenosine triphosphate-generating enzyme in the glycolytic pathway, the chemokine receptor 4 (CXCR4), the corresponding chemokine ligand 12 (CXCL12) and beta-catenin in specimens from gastric cancer patients with peritoneal carcinomatosis. In this study, the influence of PGK1 on CXCR4 and beta-catenin was assessed as well as the invasiveness of PGK1 overexpressing cancer cells. In this current study, we found that PGK1 regulates the expression of CXCR4 and beta-catenin at the mRNA and protein levels. On the other hand, CXCR4 regulates the expression of PGK1. Plasmid-mediated overexpression of PGK1 dramatically increased the invasiveness of gastric cancer cells. Interestingly, inhibition of CXCR4 in cells overexpressing PGK1 produced only a moderate reduction of invasiveness suggesting that, PGK1 itself has a critical role in tumor invasiveness. Immunohistochemistry in specimens from diffuse gastric cancer patients also revealed an overexpression of PGK1 in patients with development of peritoneal carcinomatosis. Therefore, PGK1 may be a crucial enzyme in peritoneal dissemination. Together these findings suggest that the enhanced expression of PGK1 and its signaling targets CXCR4 and beta-catenin in gastric cancer cells promote peritoneal carcinomatosis. Thus, PGK1 may serve as prognostic marker and/or be a potential therapeutic target to prevent dissemination of gastric carcinoma cells into the peritoneum.

Phosphoglycerate kinase 1 promoting tumor progression and metastasis in gastric cancer - detected in a tumor mouse model using positron emission tomography/magnetic resonance imaging.

BACKGROUND/AIMS: Tumor dissemination is frequent in gastric cancer and implies a poor prognosis. Cure is only achievable provided an accurate staging is performed at primary diagnosis. In previous studies we were able to show a relevant impact of increased phosphoglycerate kinase 1 expression (PGK1; a glycolytic enzyme) on invasive properties of gastric cancer in-vivo and in-vitro. Thus the aim of the present study was to evaluate the effect of enhanced PGK1 expression in gastric cancer employing magnetic resonance (MR)-imaging combined with positron emission tomography (PET), a recently emerging new high resolution imaging technique in a mouse model. METHODS: A metastatic nude mouse model simulating human gastric cancer behavior by orthotopic tumor implantation was established. Mice were divided into one control group (n=5) and two experimental groups (n=30) divided by half in animals baring tumors from MKN45-cells and MKN45-cells with plasmid-mediated overexpression of PGK1. In the course of tumor growth MR-imaging and PET/MRI fusion was performed. Successively experimental animals were examined macroscopically and histopathologically regarding growth, metastasis and PGK1 expression. RESULTS: Elevated PGK1 expression increased invasive and metastatic behavior of implanted gastric tumors significantly. MR/PET- imaging results in-vivoand subsequent ex-vivo findings concerning tumor growth and metastasis correlated excellently and could be underlined by concordant immuohistochemical PGK1 staining. CONCLUSION: Consistent in-vivo findings suggest that PGK1 might be crucially involved in gastric malignancy regarding growth and metastasis, which was also underlined by novel imaging techniques. Thus, PGK1 may be exploited as a prognostic marker and/or be of potential therapeutic value preventing malignant dissemination.

Transient lower esophageal sphincter relaxation and esophageal motor response.

BACKGROUND: Gastroesophageal reflux is caused by transient lower esophageal sphincter relaxations (TLESRs) in healthy individuals and in most patients with gastroesophageal reflux disease (GERD). Refluxate is normally propelled by pharyngeally induced swallowing events, but TLESRs may also be accompanied by retrograde esophageal motor responses (EMRs). These contractions have not previously been investigated and their effect on esophageal clearance is not known. The aim of this study was to assess the frequency of EMRs after TLESR in healthy individuals and GERD patients and to develop an animal model for further investigation of EMRs. MATERIALS AND METHODS: The frequency of TLESRs and esophageal body contractions after TLESRs was assessed using ambulatory manometry in five healthy individuals and five GERD patients. An animal model was developed for reproducible provocation of TLESRs and subsequent EMRs. RESULTS: Patients with GERD have significantly more TLESRs than healthy individuals. However, post-TLESR EMRs were not more frequent in the GERD group. All post-TLESR EMRs presented as simultaneous contractions of the esophagus. The feline model allowed reproducible initiation of the esophageal motor response after TLESR, showing that EMRs can be induced by external mechanoreceptor stimulation simultaneously with LES relaxation. This experimental design imitates the conditions after fundoplication in humans. CONCLUSIONS: The study demonstrated that GERD patients have significantly more TLESRs in comparison with healthy individuals, but these were only incidental to EMRs. Further research is needed to improve our understanding of esophageal motility disorders. The animal model presented offers a feasible tool for investigating TLESR-induced esophageal motility.

The predictive value of genes of the TGF-beta1 pathway in multimodally treated squamous cell carcinoma of the esophagus.

BACKGROUND AND AIM: Pretherapeutic identification of esophageal squamous cell carcinomas (ESCCs) that are likely to respond to neoadjuvant chemoradiotherapy is important in the attempt to improve the prognosis for patients. In the present study, expression of members of the transforming growth factor-beta1 (TGF-beta1) signaling pathway was investigated in pretherapeutic biopsies from 97 ESCCs (cT3, cN0/+, cM0) in patients who underwent neoadjuvant chemoradiotherapy (45 Gy plus cisplatin and 5-fluorouracil) and subsequent esophagectomy in the setting of a single-center prospective treatment trial. MATERIALS AND METHODS: Expression of TGF-beta1 and its downstream effectors Smad4 and Smad7 was assessed using quantitative reverse transcription polymerase chain reaction from RNA prepared from pretherapeutic tumor biopsies. The presence of phosphorylated Smad2 was assessed immunohistochemically. RESULTS: Expression of TGF-beta1 (mean 7.8; range 0.0-25.7 arb. units), Smad4 (mean 0.1; range 0.0-0.4 arb. units), and Smad7 (mean 1.6; range 0.4-16.1 arb. units) varied substantially between the patients. Tumors with total or subtotal regression, as determined by histopathological examination after neoadjuvant chemoradiotherapy, showed significantly higher levels of Smad4 mRNA expression than tumors with minor or no regression (P = 0.032). TGF-beta1 and Smad7 mRNA expression as well as Smad2 protein expression were of no prognostic value. Expression of the four genes under analysis also showed no impact on the overall survival. In contrast, the overall survival correlated significantly with histopathological regression (P < 0.0001) and to a minor degree also with clinical regression grading (P = 0.0254). INTERPRETATION: Among the parameters analyzed, only Smad4 was found to have possible predictive value for esophageal squamous cell carcinoma in patients receiving neoadjuvant chemoradiotherapy.

[COVID-19 cluster study at a teaching hospital]. / COVID-19-Cluster-Studie an einem Lehrkrankenhaus : Corona-Pandemie 2020.

On Mar 11th, 2020, the World Health Organization (WHO) stated in its Situation Report - 51 Coronavirus disease 2019 (COVID-19) as a pandemic. In early April 2020, a teaching hospital underwent shutdown and quarantine due to an outbreak of infection in accordance with Section 6 of the Infection Protection Act (index patient and 5 infected nursing staff). The complete staff (physicians, nurses and nonmedical personnel [NMP]) underwent COVID-19 testing within two phases: (1) between Apr 3rd and 5th, 2020 [n=1170], followed by (2) between Apr 8th and 9th, 2020 [n=953] with COVID-19 silent carrier positivity rates in accordance to testing phases of (1) n=19 (1.6%) and (2) n=25 (2.6%). The cumulative infection rate for NMP (1.6%), doctors (3.8%) and nurses (9.7%) was connected to type and extent of COVID-19 patient contact. Despite COVID-19 positivity of 34.8% (46 of 132 beds), a risk-free management of hospital operation is possible to a certain extent if hygiene regulations and strict patient selection are followed. However, a COVID-19-free clinic cannot be expected due to silent carriers.

Distinct functionality of tumor cell-derived gelatinases during formation of liver metastases.

The specific spatiotemporal role of the matrix metalloproteinase 2 (MMP-2) and MMP-9 (gelatinase) during metastasis is still under debate. Host cells have been described as major contributors to these MMPs during metastasis. Here, we show strong overexpression of MMP-2 and MMP-9 by tumor cells of clinical liver specimen of recurrent metachronous metastases, leading us to address the importance of tumor cell-derived MMP-2 or MMP-9 during liver metastasis. Thus far, distinction of their roles was impossible due to lack of inhibitors which can act exclusively on tumor cells or distinguish MMP-2 from MMP-9. We therefore used short hairpin RNA interference technology in the well-established syngeneic L-CI.5s lymphoma model, in which we could analyze the time course of experimental liver colonization (arrest/invasion of single tumor cells, outgrowth, and invasion within the parenchyma) in immunocompetent mice and correlate these steps with MMP-2 or MMP-9 expression levels. In parental tumor cells, MMP-9 expression closely correlated with the invasive phases of liver colonization, whereas MMP-2 expression remained unaltered. Specific knockdown of MMP-9 revealed a close correlation between invasion-dependent events and tumor cell-derived MMP-9 expression. In contrast, knockdown of MMP-2 did not significantly alter the metastatic potential of the cells but led to a marked inhibition of metastatic foci growth. These findings explain the efficacy of gelatinase-specific synthetic inhibitors on invasion and growth of tumor cells and attribute distinct functions of MMP-2 and MMP-9 to aspects of liver metastasis.

Local peritonectomy highly attracts free floating intraperitoneal colorectal tumour cells in a rat model.

BACKGROUND/AIMS: Intraperitoneal free cancer cells are associated with a higher risk of recurrence and a poorer prognosis in colorectal surgery. Tumour recurrence may occur early after surgery. One potential mechanism is the ability of peritoneal lesions to attract tumour cells. METHODS: In Wag-Rija rats, the parietal peritoneum was resected on a defined area, a corresponding control area was marked in the same rat and colorectal tumour cells (CC531) were applied into the abdomen after surgery. Tissue was harvested 6 or 9 days after surgery to evaluate intra-abdominal tumour growth. Additionally tumour cells were applied 2 weeks after peritoneal resection to investigate tumour growth in a healed area of peritonectomy. Specimens were evaluated for macroscopic tumour spread, weight of the abdominal wall and maximal tumour thickness. RESULTS: Macroscopic tumour spread, weight of the abdominal wall and maximal tumour thickness were significantly increased within the area of peritonectomy after both 6 and 9 days compared to the control area. However, only macroscopic tumour expansion was significantly increased in the healed area of peritonectomy. CONCLUSION: Peritoneal defects may play an important role in the pathogenesis of tumour implantation and might have some impact on tumour recurrence. The peritoneal damage should be kept as low as possible.

IDO1 and IDO2 are expressed in human tumors: levo- but not dextro-1-methyl tryptophan inhibits tryptophan catabolism.

OBJECTIVES: Indoleamine-2,3-Dioxygenase (IDO) is an immunosuppressive molecule inducible in various cells. In addition to classic IDO (IDO1), a new variant, IDO2, has recently been described. When expressed in dendritic cells (DCs) or cancer cells, IDO was thought to suppress the immune response to tumors. A novel therapeutic approach in cancer envisages inhibition of IDO with 1-methyl-tryptophan (1MT). The levo-isoform (L-1MT) blocks IDO1, whereas dextro-1MT (D-1MT), which is used in clinical trials, inhibits IDO2. Here we analyze IDO2 expression in human cancer cells and the impact of both 1-MT isoforms on IDO activity. METHODS: Surgically extirpated human primary tumors as well as human cancer cell lines were tested for IDO1 and IDO2 expression by RT-PCR. IDO1 activity of Hela cells was blocked by transfection with IDO1-specific siRNA and analysed for tryptophan degradation by RP-HPLC. The impact of D-1MT and L-1MT on IDO activity of Hela cells and protein isolates of human colon cancer were studied. RESULTS: Human primary gastric, colon and renal cell carcinomas constitutively expressed both, IDO1 and IDO2 mRNA, whereas cancer cells lines had to be induced to by Interferon-gamma (IFN-gamma). Treatment of Hela cells with IDO1-specific siRNA resulted in complete abrogation of tryptophan degradation. Only L-1MT, and not D-1MT, was able to block IDO activity in IFN-gamma-treated Hela cells as well as in protein isolates of primary human colon cancer. CONCLUSIONS: Although IDO2 is expressed in human tumors, tryptophan degradation is entirely provided by IDO1. Importantly, D-1MT does not inhibit the IDO activity of malignant cells. If ongoing clinical studies show a therapeutic effect of D-1MT, this cannot be attributed to inhibition of IDO in tumor cells.