Role of adjuvant therapy in surgically resected colorectal carcinoma

Overexpression of Srcin1 contributes to the growth and metastasis of colorectal cancer

The adaptor protein Srcin1 is a novel Src-binding protein that regulates Src activation through C-terminal Src kinase (Csk). Srcin1 behaves as a tumour suppressor in breast cancer, but the role of Srcin1 in the development of colorectal cancer (CRC) remains unknown. In the present study, Srcin1 expression in normal tissue was examined by tissue microarray and assessed by immunohistochemistry in 10 patients. In addition, the biological impact of Srcin1 knockdown on CRC cells was investigated in vitro and in vivo. The results showed that Srcin1 was expressed in different types of normal human tissues, whereas its expression was increased in human CRC tissues. Srcin1 expression also correlated with tumour progression. The suppression of Srcin1 induced cell differentiation and G0/G1 cell cycle arrest. Furthermore, Srcin1 increased cell growth as well as the capacity of migration and invasion in CRC cells. Srcin1 induced the activation of the Wnt/β-catenin signalling pathway. Moreover, Srcin1 suppression sensitized cancer cells to 5-fluorouracil (5-FU)-induced apoptosis in vitro and in vivo. Together, these results demonstrate that Srcin1 contributes to CRC carcinogenesis, invasion and metastasis. These findings provide a rationale for a mechanistic approach to CRC treatment based on the development of Srcin1-targeted therapies.

Molecular staging individualizing cancer management

Although the most important prognostic and predictive marker in colorectal cancer is tumor cells in lymph nodes, approximately 30% of patients who are node-negative die from occult metastases. Molecular staging employing specific markers and sensitive detection technologies has emerged as a powerful platform to assess prognosis in node-negative colon cancer. Integrating molecular staging into algorithms that individualize patient management will require validation and the definition of relationships between occult tumor cells, prognosis, and responses to chemotherapy.

Molecular staging estimates occult tumor burden in colorectal cancer

Tumor cells in regional lymph nodes are a key prognostic marker of survival and predictive marker of response to adjuvant chemotherapy in colorectal cancer. However, clinicopathologic techniques to detect lymph node metastases remain imperfect, and approximately 30% of patients with lymph nodes negative by histology (pN0) develop recurrent disease, reflecting occult metastases that escape detection. These observations underscore an unmet clinical need for accurate approaches to identify occult nodal metastases in colorectal cancer patients. GUCY2C is a receptor whose expression normally is restricted to intestinal epithelial cells, but is universally overexpressed by colorectal cancer cells. A prospective, multicenter, blinded clinical trial established the prognostic utility of GUCY2C qRT-PCR to detect occult nodal metastases in pN0 colorectal cancer patients. Molecular staging revealed that approximately 13% of pN0 patients were free of cancer cells, while approximately 87% had GUCY2C results that suggested occult metastases. The presence of occult nodal metastases was the most powerful independent predictor of time to recurrence and disease-free survival. These observations establish the utility of molecular detection of occult nodal metastases for assessing prognostic risk in pN0 colorectal cancer patients. Advancing GUCY2C into staging paradigms in clinical laboratories will require validation in independent patient populations, definition of the relationship between the quantity of occult tumor metastases and risk, and determination of the utility of GUCY2C qRT-PCR to identify pN0 patients who might benefit from adjuvant chemotherapy.

GUCY2C reverse transcriptase PCR to stage pN0 colorectal cancer patients

The most important prognostic marker of survival and predictive marker of response to adjuvant chemotherapy in colon cancer patients is tumor cells in regional lymph nodes. Despite their importance, standard techniques to assess nodal metastases remain imperfect, as approximately 30% of patients with histology-negative lymph nodes (pN0) die of recurrent disease, reflecting occult metastases that escape detection. These observations highlight the clinical need for novel, accurate approaches to detect occult lymph node metastases in patients with colon cancer. GUCY2C is a biomarker whose expression normally is restricted to intestinal cells, but is near universally overexpressed by colorectal cancer cells. Recently, a prospective, multicenter, blinded clinical trial demonstrated for the first time that the prognostic utility of GUCY2C quantitative reverse transcriptase (qRT)-PCR to detect occult lymph node metastases in pN0 colorectal cancer patients. Molecular staging revealed that approximately 13% of pN0 patients were free of tumor cells, while approximately 87% had GUCY2C results that suggested occult metastases. The presence of occult lymph node metastases was the strongest independent predictor of time to recurrence and disease-free survival. These observations establish the utility of molecular detection of occult lymph node metastases for estimating prognostic risk in pN0 colorectal cancer patients. Advancing this molecular diagnostic into staging paradigms in clinical laboratories will require validation in independent patient populations, definition of the relationship between the quantity of occult tumor metastases and risk, and determination of the utility of GUCY2C qRT-PCR to identify pN0 patients who might benefit from adjuvant chemotherapy.

Guanylyl cyclase C: a molecular marker for staging and postoperative surveillance of patients with colorectal cancer

Staging patients with colorectal cancer defines their prognosis and therapeutic management. Unfortunately, histopathology, the current standard for staging, is relatively insensitive for detecting occult micrometastases and a significant fraction of patients are understaged and, consequently, undertreated. Similarly, current approaches to postoperative surveillance of patients with colorectal cancer detect disease recurrence at a point when interventions have little impact on survival. The detection of rare cells in tissue, for accurately staging patients, and in blood, for detecting disease recurrence, could be facilitated by employing sensitive and specific markers of disease. Guanylyl cyclase C (GCC), the receptor for the diarrheagenic bacterial heat-stable enterotoxin, is expressed selectively by cells derived from intestinal mucosa, including normal intestinal cells and colorectal tumor cells, but not by extragastrointestinal tissues and tumors. The nearly uniform expression of relatively high levels by metastatic colorectal tumors suggests that GCC may be a sensitive and specific molecular marker for metastatic colorectal cancer cells. Employing GCC reverse transcriptase PCR, occult colorectal cancer micrometastases were detected in lymph nodes that escaped detection by histopathology. Moreover, marker expression correlated with the risk of disease recurrence. Similarly, GCC reverse transcriptase PCR revealed the presence of tumor cells in blood of all patients examined with metastatic colorectal cancer and, in some studies, was associated with an increased risk of disease recurrence and mortality. These observations suggest that GCC reverse transcriptase PCR is a sensitive and specific technique for identifying tumor cells in extraintestinal sites and may be useful for staging and postoperative surveillance of patients with colorectal cancer.

Investigation of the comparative toxicity of 5-FU bolus versus 5-FU continuous infusion circadian chemotherapy with concurrent radiation therapy in locally advanced rectal cancer

PURPOSE

To compare the relative toxicities of bolus versus infusional 5-FU chemotherapy administrated concurrently during external beam irradiation in patients with locally advanced rectal cancer following surgical extirpation.

METHODS

A total of 26 eligible patients were retrospectively identified as having been treated for rectal adenocarcinoma at the Stratton VAMC between 1989 and 1997. A comparative analysis of treatment dose intensities, treatment delays and toxicities in these patients was performed.

RESULTS

Significantly less WBC toxicity was observed in the patients receiving infusional 5-FU chemotherapy. The other toxicities, with the exception of skin toxicity, were generally less frequent in the 5-FU infusional group. When the toxicities were corrected for 5-FU dose intensity, to yield toxicity per mg of 5-FU, statistically significant differences were found for hematological toxicity (WBC and platelets), and for gastrointestinal toxicity (frequency and severity of diarrhea and weight loss). The majority of patients receiving infusional 5-FU therapy were treated using a circadian pattern of treatment peaking around the time of the radiation therapy. Patients receiving infusional 5-FU were able to tolerate over twice the dose intensity as those receiving bolus administration. Local recurrence rate in all patients was 3.8% comparing favorably to other reported studies. Distant recurrence frequency was also acceptable at 34.6% for the group.

CONCLUSION

Infusional 5-FU chemotherapy compared with bolus therapy during pelvic radiation minimizes toxicity to the patient while maximizing the dose of 5-FU that can be delivered. As infusional 5-FU therapy during radiation has previously been shown to increase disease free duration and survival, infusional 5-FU should be considered as an acceptable standard of care to prevent local recurrence of rectal adenocarcinoma following its resection. Shaping this infusional 5-FU chemotherapy within the day so that most of the daily dose is delivered around the time of the radiation therapy may further modify the toxic therapeutic ratio of combined modality therapy.

Is early post-operative treatment with 5-fluorouracil possible without affecting anastomotic strength in the intestine?

Early post-operative local or systemic administration of 5-fluorouracil (5-FU) is under investigation as a means to improve outcome after resection of intestinal malignancies. It is therefore quite important to delineate accurately its potentially negative effects on anastomotic repair. Five groups (n = 24) of rats underwent resection and anastomosis of both ileum and colon: a control group and four experimental groups receiving daily 5-FU, starting immediately after operation or after 1, 2 or 3 days. Within each group, the drug (or saline) was delivered either intraperitoneally (n = 12) or intravenously (n = 12). Animals were killed 7 days after operation and healing was assessed by measurement of anastomotic bursting pressure, breaking strength and hydroxyproline content. In all cases, 5-FU treatment from the day of operation or from day 1 significantly (P<0.025) and severely suppressed wound strength; concomitantly, the anastomotic hydroxyproline content was reduced. Depending on the location of the anastomosis and the route of 5-FU administration, even a period of 3 days between operation and first dosage seemed insufficient to prevent weakening of the anastomosis. The effects of intravenous administration, though qualitatively similar, were quantitatively less dramatic than those observed after intraperitoneal delivery. Post-operative treatment with 5-FU, if started within the first 3 days after operation, is detrimental to anastomotic strength and may compromise anastomotic integrity.

Inhibition of fibroblast collagen synthesis and proliferation by levamisole and 5-fluorouracil

Experimental studies indicate that anastomotic healing in the intestine is compromised by the immediate postoperative administration of 5-fluorouracil and levamisole. Since fibroblast functions are crucial to healing, we investigated the effects of (combinations of) both drugs on proliferation and collagen synthesis of rat skin fibroblasts in vitro. Proliferation was measured in actively dividing cells by cellular [3H]thymidine uptake and collagen synthesis in non-dividing cells by [3H]proline incorporation into collagenase-digestible protein. 5-Fluorouracil strongly and significantly (P < 0.05) reduced DNA synthesis and collagen synthesis at concentrations of 1 microM or more. The latter effect was not specific for collagen since total protein production was affected similarly. Both effects depended on the duration of exposure to the drugs. Levamisole also inhibited fibroblast proliferation dose-dependently, but less effectively than 5-fluorouracil: 50% inhibition was observed at approximately 0.1 mM. Collagen synthesis was unaffected by levamisole. If levamisole was added together with a low (0.1 microM) concentration of 5-fluorouracil, which in itself did not decrease thymidine incorporation, levamisole's antiproliferative effects became apparent at concentrations as low as 1 microM. A similar effect, but at a much higher concentration (1 mM) was noted on fibroblast collagen synthesis. These results indicate that levamisole potentiates 5-fluorouracil effects in fibroblast cultures and that direct effects of these drugs, alone or in combination, on fibroblast proliferation and collagen synthesis may be responsible for their negative influence on wound repair.

Prognostic value of tumour-infiltrating lymphocytes (TILs) in colorectal cancer

Clinical follow-up data of 276 colorectal adenocarcinoma patients treated in Kuopio University Hospital between 1976 and 1986 and followed up for a mean of 14 years were analysed. The clinical findings were correlated with tumour-infiltrating lymphocytes (TILs) and with histological and quantitative factors including nuclear parameters and volume-corrected mitotic index. In univariate survival analysis, TNM classification, Dukes' stage, histological grade, and TILs were significant predictors of survival. TNM classification, Dukes' stage, and TILs also predicted recurrence-free survival. In multivariate analysis, TILs were an independent prognostic factor of survival in all cases, as well as in patients with T1-4N0-3M0 and T1-4N1-3M1. TILs also independently predicted recurrence-free survival. TILs can provide important prognostic information in colorectal cancer to be used in evaluating for adjuvant therapy in different tumour stages.

Detection of disseminated tumor cells in peripheral blood of colorectal cancer patients

All cancer staging systems seek to identify clinical and pathological features that can predict outcome or guide therapy. In particular, a non-invasive method for the early detection of disseminating disease would be of great interest. We investigated the use of cytokeratin genes expression to detect blood metastases from colorectal tumors. Epithelial tumor cells were isolated from whole blood using the monoclonal antibody (MAb) BerEP4 and magnetic beads, and detected by reverse transcription-polymerase chain reaction using oligonucleotides derived from the cDNA sequences of cytokeratins 8, 19 and 20. The sensitivity of this assay was determined by spiking SW620 colon carcinoma cells in normal blood. Using cytokeratin 19 expression we were able to detect 1 epithelial tumor cell in 1 ml of whole blood. The clinical applicability of this technique was explored by evaluating patients with a colorectal carcinoma. Epithelial cells were detected in the blood of 12 out of 23 patients, 2 (20%) of 10 with Astler-Coller stage A or B, and 10 (77%) of 13 with stage C or D cancer. In conclusion, this test is a non-invasive, sensitive, and specific assay for detecting circulating epithelial cells in blood. It may be useful for the early diagnosis of disseminating disease, to determine whether the presence of micrometastatic cells at the time of surgery is correlated with an early relapse and for monitoring adjuvant therapeutic trials.

Prognostic value of tumour-infiltrating lymphocytes (TILs) in colorectal cancer

Clinical follow-up data of 276 colorectal adenocarcinoma patients treated in Kuopio University Hospital between 1976 and 1986 and followed up for a mean of 14 years were analysed. The clinical findings were correlated with tumour-infiltrating lymphocytes (TILs) and with histological and quantitative factors including nuclear parameters and volume-corrected mitotic index. In univariate survival analysis, TNM classification, Dukes' stage, histological grade, and TILs were significant predictors of survival. TNM classification, Dukes' stage, and TILs also predicted recurrence-free survival. In multivariate analysis, TILs were an independent prognostic factor of survival in all cases, as well as in patients with T1-4N0-3M0 and T1-4N1-3M1. TILs also independently predicted recurrence-free survival. TILs can provide important prognostic information in colorectal cancer to be used in evaluating for adjuvant therapy in different tumour stages.