Search

Abstract Background Treatment of solid tumors with vascular disrupting agent OXi4503 results in over 90% tumor destruction. However, a thin rim of viable cells persists in the tumor periphery following treatment, contributing to subsequent recurrence. This study investigates inherent differences in the microenvironment of the tumor periphery that contribute to treatment resistance. Methods Using a murine colorectal liver metastases model, spatial morphological and molecular differences within the periphery and the center of the tumor that may account for differences in resistance to OXi4503 treatment were investigated. H&E staining and immunostaining were used to examine vessel maturity and stability, hypoxia and HIF1α levels, accumulation of immune cells, expression of proangiogenic factors/receptors (VEGF, TGF-β, b-FGF, and AT1R) and expression of EMT markers (ZEB1, vimentin, E-cadherin and β-catenin) in the periphery and center of established tumors. The effects of OXi4503 on tumor vessels and cell kinetics were also investigated. Results Significant differences were found between tumor periphery and central regions, including association of the periphery with mature vessels, higher accumulation of immune cells, increased growth factor expression, minimal levels of hypoxia and increased evidence of EMT. OXi4503 treatment resulted in collapse of vessels in the tumor center; however vasculature in the periphery remained patent. Similarly, tumor apoptosis and proliferation were differentially modulated between centre and periphery after treatment. Conclusions The molecular and morphological differences between tumor periphery and center may account for the observed differential resistance to OXi4503 treatment and could provide targets for drug development to totally eliminate metastases.

Abstract Background Preliminary experimental studies have suggested that the in situ destruction of tumor tissue by local laser ablation (LA) may also stimulate host immunity against cancer. We investigated local and systemic induction of immune responses after laser ablation in the setting of residual tumor. Methods A murine colorectal cancer (CRC) liver metastasis model was used. Selected tumors of liver CRC bearing mice and livers of mice without tumor induction were treated with LA. Liver and tumor tissues from the ablation sites and from distant sites were collected at various time points following LA and changes in CD3+ T cells and Kupffer cells (F4/80 marker) infiltration and the expression of interferon gamma (IFNγ) were investigated by immunohistochemistry and ELISpot. Base line levels of CD3+ T cells and Kupffer cells were established in untreated mice. Results The presence of tumor induced significant accumulation of CD3+ T cells and Kupffer cells at the tumor-host interface, within the tumor vascular lakes and increased their baseline concentration within the liver parenchyma. LA of the liver induced accumulation of CD3+ T-cells and Kupffer cells at the site of injury and systemic induction of immune responses as discerned by the presence of IFNγ secreting splenocytes. LA of liver tumors induced significant increase of CD3+ T-cells at site of injury, within normal liver parenchyma, and the tumor-host interface of both ablated and distant tumors. In contrast Kupffer cells only accumulated in ablated tumors and the liver parenchyma but not in distant tumors. IFNγ expression increased significantly in ablated tumors and showed an increasing trend in distant tumors. Conclusion Laser ablation in addition to local tumor destruction induces local and systemic Th1 type immune responses which may play a significant role in inhibiting tumor recurrence from residual micrometastases or circulating tumor cells.

Background: Preliminary experimental studies have suggested that the in situ destruction of tumor tissue by local laser ablation (LA) may also stimulate host immunity against cancer. We investigated local and systemic induction of immune responses after laser ablation in the setting of residual tumor.Methods: A murine colorectal cancer (CRC) liver metastasis model was used. Selected tumors of liver CRC bearing mice and livers of mice without tumor induction were treated with LA. Liver and tumor tissues from the ablation sites and from distant sites were collected at various time points following LA and changes in CD3+ T cells and Kupffer cells (F4/80 marker) infiltration and the expression of interferon gamma (IFNγ) were investigated by immunohistochemistry and ELISpot. Base line levels of CD3+ T cells and Kupffer cells were established in untreated mice.Results: The presence of tumor induced significant accumulation of CD3+ T cells and Kupffer cells at the tumor-host interface, within the tumor vascular lakes and increased their baseline concentration within the liver parenchyma. LA of the liver induced accumulation of CD3+ T-cells and Kupffer cells at the site of injury and systemic induction of immune responses as discerned by the presence of IFNγ secreting splenocytes. LA of liver tumors induced significant increase of CD3+ T-cells at site of injury, within normal liver parenchyma, and the tumor-host interface of both ablated and distant tumors. In contrast Kupffer cells only accumulated in ablated tumors and the liver parenchyma but not in distant tumors. IFNγ expression increased significantly in ablated tumors and showed an increasing trend in distant tumors.Conclusion: Laser ablation in addition to local tumor destruction induces local and systemic Th1 type immune responses which may play a significant role in inhibiting tumor recurrence from residual micrometastases or circulating tumor cells. [ABSTRACT FROM AUTHOR]

Abstract Background Standard non-steroidal anti-inflammatory drugs (NSAIDs) reduce the risk of colorectal cancer; however, their use as preventive agents is limited by their inherent toxicity. Drugs that selectively inhibit cyclooxygenase-2 (COX-2) may be useful in this setting as they are supposedly less toxic. No study has directly compared the ability of standard NSAIDs and selective COX-2 inhibitors to inhibit colorectal cancer at clinically relevant doses. Methods Aberrant crypt foci (ACF) were induced in Sprague–Dawley rats by using 1,2-dimethylhydrazine (DMH). Test agents or vehicle were then administered for 3 weeks, twice daily through orogastric gavage. At the end of this period, the number and multiplicity of ACF were determined. The agents tested at equivalent anti-inflammatory doses were: sulindac and indomethacin (standard NSAIDs), meloxicam (selective COX-2 inhibitor), celecoxib (specific COX-2 inhibitor) and sulindac sulfone (no known COX activity). Acute gastrotoxicity of NSAID in rats was compared by using quantitative histology. Results All test agents reduced the number of ACF. There was a 42% reduction with indomethacin, 46% with sulindac, 46% with meloxicam, 22% with celecoxib and 36% with sulindac sulfone. Only the COX-2 inhibitors caused no significant gastrotoxicity in rats. Conclusions Cyclooxygenase-2 inhibitors are potentially ideal chemopreventive agents as they inhibit ACF and are not gastrotoxic. [ABSTRACT FROM AUTHOR]

Abstract Background Standard non-steroidal anti-inflammatory drugs (NSAIDs) reduce the risk of colorectal cancer; however, their use as preventive agents is limited by their inherent toxicity. Drugs that selectively inhibit cyclooxygenase-2 (COX-2) may be useful in this setting as they are supposedly less toxic. No study has directly compared the ability of standard NSAIDs and selective COX-2 inhibitors to inhibit colorectal cancer at clinically relevant doses. Methods Aberrant crypt foci (ACF) were induced in Sprague–Dawley rats by using 1,2-dimethylhydrazine (DMH). Test agents or vehicle were then administered for 3 weeks, twice daily through orogastric gavage. At the end of this period, the number and multiplicity of ACF were determined. The agents tested at equivalent anti-inflammatory doses were: sulindac and indomethacin (standard NSAIDs), meloxicam (selective COX-2 inhibitor), celecoxib (specific COX-2 inhibitor) and sulindac sulfone (no known COX activity). Acute gastrotoxicity of NSAID in rats was compared by using quantitative histology. Results All test agents reduced the number of ACF. There was a 42% reduction with indomethacin, 46% with sulindac, 46% with meloxicam, 22% with celecoxib and 36% with sulindac sulfone. Only the COX-2 inhibitors caused no significant gastrotoxicity in rats. Conclusions Cyclooxygenase-2 inhibitors are potentially ideal chemopreventive agents as they inhibit ACF and are not gastrotoxic. [ABSTRACT FROM AUTHOR]

Background: Ablation of liver tumours by focal hyperthermia causes tissue injury not only by direct effects, but also by progressive tissue damage following the initial heat application. The mechanism by which this progressive injury occurs remains undefined. Stimulation of apoptosis following the initial heat stimulus may be involved in this progression. The role of apoptosis in the subsequent progression of focal hyperthermia injury was investigated in liver and colorectal liver metastases in a murine model., Materials and Methods: Focal hyperthermia produced by laser (Nd-YAG--wavelength 1064 nm) was applied to the liver and colorectal liver metastases in CBA mice (2 Watts for 50 seconds). The animals were killed at 0, 12, 24, 48, 72, 120 and 168 hours after the application of focal hyperthermia. Haematoxylin and eosin staining and immunohistochemistry were performed on paraffin sections to assess the extent of tissue necrosis. Apoptosis was examined by assessment of DNA fragmentation using terminal deoxynucleotidyl transferase d-uridine triphosphate nick end labelling (TUNEL) and activated Caspase 3 immunostaining. The sequence of the apoptotic response was determined at the treated tissue margins and compared to untreated liver and tumour., Results: Focal hyperthermia produced progressive tissue injury in both liver and colorectal liver metastases. TUNEL labelling was less specific than activated Caspase 3 in detecting apoptotic cells. Apoptosis was detected and peaked at 12 hours following therapy based on activated Caspase 3 staining, before returning to baseline at 72 hours. In tumour tissue, the apoptotic response was more sustained, peaking at 24 hours before returning to baseline levels by 96 hours following therapy., Conclusion: Increased apoptosis occurs following the application of focal hyperthermia to normal liver and colorectal metastases. The apoptotic response is more sustained in tumour tissue and contributes to the progressive injury that is evident after the initial heat stimulus.