The annual report to the nation on the status of cancer, 1973-1997, with a special section on colorectal cancer

Racial disparity in colorectal cancer: Gut microbiome and cancer stem cells

Over the past two decades there has been remarkable progress in cancer diagnosis, treatment and screening. The basic mechanisms leading to pathogenesis of various types of cancers are also understood better and some patients, if diagnosed at a particular stage go on to lead a normal pre-diagnosis life. Despite these achievements, racial disparity in some cancers remains a mystery. The higher incidence, aggressiveness and mortality of breast, prostate and colorectal cancers (CRCs) in African-Americans as compared to Caucasian-Americans are now well documented. The polyp-carcinoma sequence in CRC and easy access to colonic epithelia or colonic epithelial cells through colonoscopy/colonic effluent provides the opportunity to study colonic stem cells early in course of natural history of the disease. With the advent of metagenomic sequencing, uncultivable organisms can now be identified in stool and their numbers correlated with the effects on colonic epithelia. It would be expected that these techniques would revolutionize our understanding of the racial disparity in CRC and pave a way for the same in other cancers as well. Unfortunately, this has not happened. Our understanding of the underlying factors responsible in African-Americans for higher incidence and mortality from colorectal carcinoma remains minimal. In this review, we aim to summarize the available data on role of microbiome and cancer stem cells in racial disparity in CRC. This will provide a platform for further research on this topic.

Inflammation-based factors and prognosis in patients with colorectal cancer

Several parameters for predicting survival in patients with colorectal cancer have been identified, including the performance status, age, gender and tumor-node-metastasis (TNM) stage. Although the TNM stage is important and useful for predicting the prognosis and determining the appropriate treatment, it is well known that the survival time varies widely, even in patients with the same stage of disease. Therefore, the identification of new parameters capable of more precisely predicting patient survival is needed to help select the optimal treatment, especially in patients in the advanced stage of disease. Although the TNM stage reflects the tumor characteristics, cancer progression and survival are not determined solely based on the local characteristics of the tumor, but also the host systemic immune/inflammatory response. Therefore, using a combination of parameters that reflect both tumor characteristics and the host systemic inflammatory status is thought to be important for accurately predicting patient survival.

Ornithine decarboxylase gene is overexpressed in colorectal carcinoma

AIM: To investigate the ornithine decarboxylase (ODC) gene expression in colorectal carcinoma, ODC mRNA was assayed by RT-PCR and ODC protein was detected by a monoclonal antibody against fusion of human colon ODC prepared by hybridoma technology.

METHODS: Total RNA was extracted from human colorectal cancer tissues and their normal counterpart tissues. ODC mRNA levels were examined by RT-PCR. ODC genes amplified from RT-PCR were cloned into a prokaryotic vector pQE-30. The expressed proteins were purified by chromatography. Anti-ODC mAb was prepared with classical hybridoma techniques and used to determine the ODC expression in colon cancer tissues by immunohistochemical and Western blotting assay.

RESULTS: A cell line, which could steadily secrete anti-ODC mAb, was selected through subcloning four times. Western blotting reconfirmed the mAb and ELISA showed that its subtype was IgG2a. RT-PCR showed that the ODC mRNA level increased greatly in colon cancer tissues (P<0.01). Immunohistochemical staining showed that colorectal carcinoma cells expressed a significantly higher level of ODC than normal colorectal mucosa (98.6±1.03% vs 5.26±5%, P<0.01).

CONCLUSION: ODC gene overexpression is significantly related to human colorectal carcinoma. ODC gene expression may be a marker for the gene diagnosis and therapy of colorectal carcinoma.

Tumor metastasis and the reciprocal regulation of heparanase gene expression by nuclear factor kappa B in human gastric carcinoma tissue

AIM: To investigate whether NF-κB is activated in human gastric carcinoma tissues and, if so, to study whether there is any correlation between NF-κB activity and heparanase expression in gastric carcinoma.

METHODS: NF-κB activation was assayed by immunohi-stochemical staining in formalin-fixed, paraffin-embedded specimens from 45 gastric carcinoma patients. Electrophoretic mobility shift assay (EMSA) method was used for nuclear protein from these fresh tissue specimens. Heparanase gene expression was quantified using quantitative RT-PCR.

RESULTS: The nuclear translocation of RelA (marker of NF-κB activation) was significantly higher in tumor cells compared to adjacent and normal epithelial cells [(41.3±3.52)% vs (0.38±0.22) %, t = 10.993, P = 0.000<0.05; (41.3±3.52)% vs (0±0.31)%, t = 11.484, P = 0.000<0.05]. NF-κB activation was correlated with tumor invasion-related clinicopathological features such as lymphatic invasion, pathological stage, and depth of invasion (Z = 2.148, P = 0.032<0.05; χ² = 8.758, P = 0.033<0.05; χ² = 18.531, P = 0.006<0.05). NF-κB activation was significantly correlated with expression of heparanase gene (r = 0.194, P = 0.046<0.05).

CONCLUSION: NF-κB RelA (p65) activation was related with increased heparanase gene expression and correlated with poor clinicopathological characteristics in gastric cancers. This suggests NF-κB as a major controller of the metastatic phenotype through its reciprocal regulation of some metastasis-related genes.

An integrated approach to the detection of colorectal cancer utilizing proteomics and bioinformatics

AIM: To find new potential biomarkers and to establish patterns for early detection of colorectal cancer.

METHODS: One hundred and eighty-two serum samples including 55 from colorectal cancer (CRC) patients, 35 from colorectal adenoma (CRA) patients and 92 from healthy persons (HP) were detected by surface-enhanced laser desorption/ionization mass spectrometry (SELDI-MS). The data of spectra were analyzed by bioinformatics tools like artificial neural network (ANN) and support vector machine (SVM).

RESULTS: The diagnostic pattern combined with 7 potential biomarkers could differentiate CRC patients from CRA patients with a specificity of 83%, sensitivity of 89% and positive predictive value of 89%. The diagnostic pattern combined with 4 potential biomarkers could differentiate CRC patients from HP with a specificity of 92%, sensitivity of 89% and positive predictive value of 86%.

CONCLUSION: The combination of SELDI with bioinformatics tools could help find new biomarkers and establish patterns with high sensitivity and specificity for the detection of CRC.

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Racial differences in the anatomical distribution of colorectal cancer: a study of differences between American and Chinese patients

AIM: To compare the racial differences of anatomical distribution of colorectal cancer (CRC) and determine the association of age, gender and time with anatomical distribution between patients from America (white) and China (oriental).

METHODS: Data was collected from 690 consecutive patients in Cleveland Clinic Florida, U.S.A. and 870 consecutive patients in Nan Fang Hospital affiliated to the First Military Medical University, China over the past 11 years from 1990 to 2000. All patients had colorectal adenocarcinoma diagnosed by histology and underwent surgery.

RESULTS: The anatomical subsite distribution of tumor, age and gender were significantly different between white and oriental patients. Lesions in the proximal colon (P < 0.001) were found in 36.3% of white vs 26.0% of oriental patients and cancers located in the distal colon and rectum in 63.7% of white and 74% of oriental patients (P < 0.001). There was a trend towards the redistribution from distal colon and rectum to proximal colon in white males over time, especially in older patients (> 80 years). No significant change of anatomical distribution occurred in white women and Oriental patients. The mean age at diagnosis was 69.0 years in white patients and 48.3 years in Oriental patients (P < 0.001).

CONCLUSION: This is the first study comparing the anatomical distribution of colorectal cancers in whites and Chinese patients. White Americans have a higher risk of proximal CRC and this risk increased with time. The proportion of white males with CRC also increased with time. Chinese patients were more likely to have distal CRC and developed the disease at a significantly earlier age than white patients. These findings have enhanced our understanding of the disease process of colorectal cancer in these two races.

Reduction of the incidence and mortality of rectal cancer by polypectomy: a prospective cohort study in Haining County

AIM: To reduce the incidence and mortality of rectal cancer and address the hypothesis that colorectal cancer often arise from precursor lesion (s), either adenomas or non-adenomatous polyps, by conducting a population-based mass screening for colorectal cancer in Haining County, Zhejiang, PRC.

METHODS: From 1977 to 1980, physicians screened the population of Haining County using 15 cm rigid endoscopy. Of over 240000 participants, 4076 of them were diagnosed with precursor lesions, either adenomas or non-adenomatous polyps, which were then removed surgically. All individuals with precursor lesions were followed up and reexamined by endoscopy every two to five years up to 1998.

RESULTS: After the initial screening, 953 metachronous adenomas and 417 non-adenomatous polyps were detected and removed from the members of this cohort. Further, 27 cases of colorectal cancer were detected and treated. Log-rank tests showed that the survival time among those cancer patients who underwent mass screening increased significantly compared to that of other colorectal cancer patients (P < 0.0001). According to the population-based cancer registry in Haining County, age-adjusted incidence and mortality of rectal cancer decreased by 41% and 29% from 1977-1981 to 1992-1996, respectively. Observed cumulative 20-year rectal cancer incidence was 31% lower than the expected in the screened group; the mortality due to rectal cancer was 18% lower than the expected in the screened group.

CONCLUSION: Mass screening for rectal cancer and precursor lesions with protocoscopy in the general population and periodical following-up with routine endoscopy for high-risk patients may decrease both the incidence and mortality of rectal cancer.