Liesbeth M. Veenendaal

Differential Notch and TGFβ Signaling in Primary Colorectal Tumors and Their Corresponding Metastases

Background: Loss of epithelial morphology and the acquisition of mesenchymal characteristics may contribute to metastasis formation during colorectal tumorigenesis. The Wnt, Notch and TGFβ signaling pathways control tissue homeostasis and tumor development in the gut. The relationship between the activity of these pathways and the expression of epithelial and mesenchymal markers was investigated in a series of primary colorectal tumors and their corresponding metastases. Methods: Tissue samples of primary colorectal tumors, normal colonic mucosa, and regional and systemic metastases were processed for immunohistochemistry in a tissue microarray format. The expression of mesenchymal (vimentin, fibronectin) and epithelial (E-cadherin) markers was related to markers of Wnt (β-catenin), Notch (HES1) and TGFβ (phospho-SMAD2) signalling. In addition, the KRAS mutation status was assessed. Results: When compared to normal mucosa, primary colorectal tumors showed a marked increase in the levels of cytoplasmic vimentin and nuclear β-catenin, phospho-SMAD2 and HES1. Increased vimentin expression correlated with the presence of oncogenic KRAS and with nuclear β-catenin. The corresponding liver, lymph node, brain and lung metastases did not express vimentin and displayed significantly lower levels of nuclear phospho-SMAD2 and HES1, while retaining nuclear β-catenin. Conclusions: Primary colorectal carcinomas display aberrant expression of vimentin, and have activated Notch and TGFβ signaling pathways. Surprisingly, many regional and distant metastases have lost nuclear HES1 and pSMAD2, suggesting that the activity of the Notch and TGFβ pathways is reduced in secondary colorectal tumors.

Liver metastases of neuroendocrine tumours; early reduction of tumour load to improve life expectancy

BackgroundNeuroendocrine tumours frequently metastasize to the liver. Although generally slowly progressing, hepatic metastases are the major cause of carcinoid syndrome and ultimately lead to liver dysfunction, cardiac insufficiency and finally death.MethodsA literature review was performed to define the optimal treatment strategy and work-up in patients with neuroendocrine hepatic metastases. Based on this, an algorithm for the management of these patients was established.ResultsPlatelet serotonin and chromogranin A are useful biomarkers for detection and follow-up of neuroendocrine tumour. Helical computed tomography and somatostatin receptor scintigraphy are the most sensitive diagnostic modalities. Surgical debulking is an accepted approach for reducing hormonal symptoms and to establish better conditions for medical treatment, but is frequently impossible due to the extent of disease. A novel approach is the local ablation of tumour by thermal coagulation using therapies such as radiofrequency ablation (RFA) or laser induced thermotherapy (LITT). These techniques preserve normal liver tissue. There is a tendency to destroy metastases early in the course of disease, thereby postponing or eliminating the surgically untreatable stage. This can be combined with postoperative radioactive octreotide to eliminate small multiple metastases. In patients with extensive metastases who are not suitable for local destruction, systemic therapy by octreotide, 131I-MIBG treatment or targeted chemo- and radiotherapy should be attempted. A final option for selective patients is orthotopic liver transplantation.ConclusionTreatment for patients with neuroendocrine hepatic metastases must be tailored for each individual patient. When local ablative therapies are used early in the course of the disease, the occurrence of carcinoid syndrome with end stage hepatic disease can be postponed or prevented.

Transient infection of freshly isolated human colorectal tumor cells by reovirus T3D intermediate subviral particles

Reovirus T3D preferentially kills tumor cells expressing Ras oncogenes and has shown great promise as an anticancer agent in various preclinical tumor models. Here, we investigated whether reovirus can infect and kill tumor cell cultures and tissue fragments isolated from resected human colorectal tumors, and whether this was affected by the presence of endogenous oncogenic KRAS. Tissue fragments and single-cell populations isolated from human colorectal tumor biopsies were infected with reovirus virions or with intermediate subviral particles (ISVPs). Reovirus virions were capable of infecting neither single-cell tumor cell populations nor small fragments of intact viable tumor tissue. However, infection of tumor cells with ISVPs resulted in transient viral protein synthesis, irrespective of the presence of oncogenic KRAS, but this did not lead to the production of infectious virus particles, and tumor cell viability was largely unaffected. ISVPs failed to infect intact tissue fragments. Thermolysin treatment of tumor tissue liberated single cells from the tissue and allowed infection with ISVPs, but this did not result in the production of infectious virus particles. Immunohistochemistry on tissue microarrays showed that junction adhesion molecule 1, the major cellular reovirus receptor, was improperly localized in the cytoplasm of colorectal tumor cells and was expressed at very low levels in liver metastases. This may contribute to the observed resistance of tumor cells to reovirus T3D virions. We conclude that infection of human colorectal tumor cells by reovirus T3D requires processing of virions to ISVPs, but that oncolysis is prevented by a tumor cell response that aborts viral protein synthesis and the generation of infectious viral particles, irrespective of KRAS mutation status.

Dual effect of KrasD12 knockdown on tumorigenesis: increased immune-mediated tumor clearance and abrogation of tumor malignancy

Activating mutations in the human KRAS proto-oncogene are acquired during the earliest stages of colorectal cancer development. If mutant KRAS is to be used as a target for therapy in colorectal cancer, tumor growth should depend on its continued presence. Here, we report that stable knockdown of KrasD12 in murine C26 colorectal cancer cells by RNA interference resulted in loss of transformed properties in vitro. The incidence of subcutaneous tumor formation was reduced by 60% and the lag time was increased sevenfold. KrasD12-knockdown tumors grew noninvasively and did not cause morbidity. Remarkably, some of the KrasD12-knockdown tumors regressed spontaneously, which rendered these mice resistant to parental C26 tumor growth. In immune-deficient hosts, the incidence of tumor formation by KrasD12-knockdown cells was 100%. None of these tumors regressed spontaneously. We conclude that the reduced incidence of tumor formation by KrasD12-knockdown cells is due to tumor cell clearance by the host immune system, but not to an intrinsic inability of these cells to grow out as tumors. Interestingly, KrasD12 knockdown resulted in increased production of interleukin 18 (Il-18), an immune-stimulatory cytokine that has been implicated in limiting colorectal tumor formation. Thus, mutant KrasD12 suppresses Il-18 production in colorectal tumor cells, which may contribute to evasion of the local immune system during tumor development.

Multipolar radiofrequency ablation of large hepatic metastases of endocrine tumours

Radiofrequency ablation (RFA) is a reliable method of creating thermally induced coagulation necrosis. Local recurrence after RFA of hepatic metastases is directly dependent on tumour size related to the free margin of ablation. To produce larger coagulation volumes a bipolar radiofrequency device was developed that allows the simultaneous activation of three active needles. This technique was used at laparotomy in a patient with liver metastases of an endocrine tumour. Coagulation size up to 12 cm in diameter could be created. The postoperative recovery of the patient was uncomplicated. No local recurrence was seen after 13 months of follow-up with computed tomography scan. The use of simultaneously operated multiple radiofrequency electrodes in a multipolar mode expands the treatment options for patients with large and unresectable intrahepatic metastases.

Synergistic Effect of Interstitial Laser Coagulation and Doxorubicin in a Murine Tumor Recurrence Model of Solitary Colorectal Liver Metastasis

BackgroundInterstitial laser coagulation (ILC) is gaining acceptance for treatment of unresectable colorectal liver metastases. However, local recurrence rates are still high. To overcome this problem, we investigated the potential of additional systemic therapy after ILC in a murine model.MethodsSingle C26 colon carcinoma nodules (∼1 mm3) expressing firefly luciferase were implanted in the left liver lobe of 32 BALB/c mice. Seven days after implantation, tumors were treated with either ILC alone (neodymium–yttrium aluminum garnet; 6 W/cm; 800 J/cm) or ILC followed by 1 mg/kg of doxorubicin intravenously. Controls received either doxorubicin alone or sham treatment. Tumor load was measured by in vivo bioluminescent imaging.ResultsSolitary colorectal liver metastases developed over 7 days after tumor implantation in the liver. Extrahepatic disease was not observed. The ILC dose was set to ablate the liver metastases with recurrent tumor growth in 9 of 16 mice after 7 days. After ILC plus doxorubicin, complete tumor destruction occurred without recurrence (0 of 14). Sham treatment or treatment with doxorubicin alone showed an exponential increase in tumor load.ConclusionsA murine tumor recurrence model after local ablative treatment of solitary liver metastasis was developed. The combination of ILC and doxorubicin had a strong synergistic effect that led to complete tumor remission in all animals treated.

Comparison of laser- and RF based interstitial coagulation systems for the treatment of liver tumors

Hepatocellular carcinoma (HCC) is one of the most common cancers in the world. Surgical treatments, including hepatic resection and liver transplantation are considered as the most effective treatment of HCC. However, less than 20% of HCC patients can be treated surgically because of: multi-focal diseases, proximity of tumor to key vascular or biliary structures and inadequate functional hepatic reserve related coexistent cirrhosis. In this unfortunate groups of patients various palliative treatments modalities are being performed to extend the time of survival and quality of life. These techniques include trans-catheter arterial chemoembolization (TACE), percutaneous ethanol injection (PEI) and Interstitial Thermal Therapy: laser-induced interstitial thermotherapy (LITT) and radio-frequency ablation (RFA).