Chemotherapy for colorectal cancer

Bax expression is a candidate prognostic and predictive marker of colorectal cancer

OBJECTIVE

Since the anti-tumor activity of 5-fluorouracil (5-FU) is due to induction of apoptosis, we assessed the value of expression of key apoptotic molecules (Bax, Bcl-2 and p53) in predicting the efficacy of 5-FU therapy for colorectal adenocarcinomas (CRCs).

METHODS

Archival tissues of CRCs from 56 patients who received a complete regimen of 5-FU-based chemotherapy after surgery, and 56 patients matched for age, gender, ethnicity, tumor stage, tumor location, and tumor differentiation who had undergone only surgery (without any pre- or post-surgery therapy), were evaluated for immunophenotypic expression of Bax, Bcl-2, and p53. Also, these CRCs were evaluated for Bax mutations. The predictive capacity or prognostic value of these markers was assessed by estimating overall survival.

RESULTS

The majority of low Bax expressing CRCs have exhibited mutations at the G (8) tract. There was no significant difference in overall survival rates between the categories of surgery alone and 5-FU-treated patients. However, a better survival was observed for patients who received chemotherapy when their CRCs had low Bax/Bcl2 ratio (HR, 1.55; 95% CI: 1.46-31.00). Patients who received surgery alone and whose CRCs lacked Bax expression had 5.33 times higher mortality than those with high Bax expression (95% CI: 1.78-15.94), when controlled for tumor stage and other confounders. Bcl-2 and nuclear p53 accumulation had no predictive value in either patient group.

CONCLUSION

These findings are the first to demonstrate that high Bax expression is a good prognosticator for patients who underwent surgery alone, and that patient with low Bax/Bcl-2 expression ratio benefit from 5-FU-based adjuvant therapies.

Rapid evolution in colorectal cancer: therapy now and over the next five years

A large number of patients with colorectal cancer have relatively early disease, and thus, adjuvant therapy has the potential to save lives. In stage III patients, there has been a steady improvement in 3-year disease-free survival with the use of 5-fluorouracil/leucovorin (5-FU/LV) regimens and capecitabine (Xeloda); Hoffmann-La Roche Inc., Nutley, NJ, http://www.rocheusa.com) regimens. A median survival longer than 20 months was observed in patients with metastatic disease when treated with combination chemotherapy containing oxaliplatin (Eloxatin); Sanofi-Synthelabo Inc., New York, http://www.sanofi-synthelabo.us) or irinotecan (Camptosar); Pfizer Pharmaceuticals, New York, http://www.pfizer.com). This has led to 5-FU/LV/oxaliplatin becoming standard therapy, along with 5-FU/LV/irinotecan. New data confirm the beneficial effect on disease-free survival of adding oxaliplatin to adjuvant colorectal cancer regimens based on 5-FU. These regimens show an effect when given in bolus as well as in infusional schedules. Interest in future adjuvant regimens focuses on the potential additional benefit of molecularly targeted agents, such as bevacizumab (Avastin); Genentech, Inc., South San Francisco, CA, http://www.gene.com), and on the ability of applied genomics to distinguish between high- and low-risk populations.

Adjuvant therapy for colon cancer

As there have been advances in the treatment of metastatic colorectal cancer, exciting developments have also been achieved in the adjuvant treatment of colon cancer. At the same time, more questions have been raised, and some controversies remain. The results of the MOSAIC trial demonstrated the benefit of adding oxaliplatin to 5-fluorouracil (5-FU) and leucovorin (FOLFOX) in adjuvant therapy for stage II and III disease, but the optimal duration of therapy and the management of toxicities remain to be resolved. Capecitabine is at least equivalent to the Mayo Clinic bolus 5-FU and leucovorin regimen in the adjuvant treatment of stage III colon cancer with a lower incidence profile of adverse events, allowing additional options for patients and physicians. Routine adjuvant systemic therapy in all patients with stage II colon cancer is still debatable. Although a statistically significant advantage for adjuvant treatment in stage II disease was shown for the first time from a large randomized study (QUASAR), the subsets of patients who truly benefit from therapy need to be identified. The application of pharmacogenetics and pharmacogenomics in adjuvant therapy for colorectal cancer will help to distinguish those patients with risk factors and to guide individualized therapy.

Dual inhibition of epidermal growth factor receptor and vascular endothelial growth factor receptor phosphorylation by AEE788 reduces growth and metastasis of human colon carcinoma in an orthotopic nude mouse model

We studied growth factors and their receptors in tumor cells and tumor-associated endothelial cells as the therapeutic targets in colon cancer. Immunohistochemical analysis of 13 surgical specimens of human colon adenocarcinoma revealed that both tumor cells and tumor-associated endothelial cells in 11 of the 13 specimens expressed the epidermal growth factor (EGF), transforming growth factor alpha (TGF-alpha), EGF receptor (EGFR), phosphorylated EGFR (pEGFR), vascular endothelial growth factor (VEGF), VEGF receptor (VEGFR), and phosphorylated VEGFR (pVEGFR). HT29 human colon cancer cells growing orthotopically in the cecum of nude mice expressed a high level of EGF, EGFR, pEGFR, VEGF, VEGFR, and pVEGFR. Double-immunofluorescence staining found that tumor-associated mouse endothelial cells also expressed pEGFR and pVEGFR. Tumors in mice treated for 5 weeks with oral AEE788 (an inhibitor of EGFR and VEGFR tyrosine kinase) as a single agent or with CPT-11 alone were smaller (>50%) than those in control mice. Mice treated with the combination of AEE788 and CPT-11 had significantly smaller tumors (P < 0.01) and complete inhibition of lymph node metastasis. AEE788 alone or in combination with CPT-11 inhibited pEGFR, pVEGFR, and phosphorylated Akt expression on tumor-associated endothelial cells as well as on tumor cells. The combination therapy also significantly decreased microvessel density and tumor cell proliferation and increased the level of apoptosis in both tumor cells and tumor-associated endothelial cells. Collectively, these data suggest that the dual inhibition of EGFR and VEGFR signaling pathways in tumor cells and tumor-associated endothelial cells in combination with chemotherapy can provide a new approach to the treatment of colon cancer.

Monoclonal antibodies in the treatment of colorectal cancer

Monoclonal antibodies have been developed to target specific proteins involved in the development and progression of cancer. These reagents have the advantage of exquiste specificity, and as currently engineered, low toxicity. The impact monoclonal antibody therapy has recently been demonstrated in colorectal cancer, in which two pathways critical to carcinogenesis have been targeted. The targets are the epidermal growth factor receptor signaling pathway and angiogenesis. Antibodies directed to proteins in both pathways have shown significant activity especially in combination with chemotherapy, and studies in the adjuvant setting are in progress. We review the use of monoclonal antibodies in the treatment of colorectal cancer with particular attention to edrecolomab (Mab 17-1A), bevacizumab (Avastin), cetuximab (IMC-C225), ABX-EGF and EMD 72000. Additional compounds are in earlier stages of development, and the future of this approach in solid tumours is promising.