Judith A. McKay

Matrix metalloproteinase‐1 is associated with poor prognosis in oesophageal cancer

The matrix metalloproteinases (MMPs) are a family of closely related proteolytic enzymes which are involved in the degradation of different components of the extracellular matrix. There is increasing evidence to indicate that individual MMPs have an important role in tumour invasion and tumour spread. Monoclonal antibodies specific for MMP‐1, MMP‐2, or MMP‐9 have been produced, using as immunogens peptides selected from the amino acid sequences of individual MMPs. The presence of MMP‐1, MMP‐2, and MMP‐9 in oesophageal cancer was investigated by immunohistochemistry on formalin‐fixed, wax‐embedded sections of oesophageal cancers. The relationship of individual MMPs to prognosis and survival was determined. MMP‐1 was present in 24 per cent of oesophageal cancers, while MMP‐2 and MMP‐9 were present in 78 and 70 per cent of tumours, respectively. The presence of MMP‐1 was associated with a particularly poor prognosis (log rank test 8·46, P<0·004) and was an independent prognostic factor (P=0·02). The identification of individual MMPs in oesophageal cancer provides a rational basis for use in the treatment of oesophageal cancer of MMP inhibitors which are currently undergoing clinical trial.

Cyclin D1 protein expression and gene polymorphism in colorectal cancer

Cyclin D1 is a key cell cycle regulatory protein, the expression and subcellular localization of which is often altered in human tumor cells. A common A/G single nucleotide polymorphism (A870G) in exon 4 of the cyclin D1 gene, CCND1, is associated with the presence of 2 distinct mRNA transcripts for this G1/S regulatory protein, and CCND1 genotype has been related to prognosis in lung cancer and head and neck carcinoma. We have investigated both the expression of cyclin D1 protein and the CCND1 A870G polymorphism in 100 colorectal cancer patients. Immunohistochemistry demonstrated cyclin D1 protein expression in 55% of tumors, and while the absence of cyclin D1 protein was not associated with outcome (p=0.81), high levels of protein expression (>50% of tumor cells expressing cyclin D1) correlated with significantly shortened overall survival (p=0.01). Using polymerase chain reaction restriction fragment length polymorphism analysis, we determined the frequency of each genotype and found that CCND1 genotype was not related to overall survival (p>0.05). In addition, genotype was unrelated to the level of expression and localization of cyclin D1 protein, as well as other key G1/S checkpoint proteins (p21, p27, p53, retinoblastoma) and tumor proliferation markers (proliferating cell nuclear antigen). However, higher levels of p27, and to a lesser extent p21, were associated with reduced cytoplasmic cyclin D1 protein (p=0.029 and p=0.054, respectively). In conclusion, we have demonstrated that high levels of cyclin D1 protein expression are related to outcome in colorectal cancer; however, the CCND1 A870G polymorphism is unrelated to either cyclin D1 protein expression or patient survival. Int. J. Cancer 88:77–81, 2000.

Expression of cytochrome P450 CYP1B1 in breast cancer

The expression of CYP1B1 has been identified in breast cancer using the reverse transcriptase‐polymerase chain reaction and immunoblotting. CYP1B1 mRNA was expressed in the majority of breast tumours and immunoblotting of breast tumours identified a single protein band of molecular weight 60 kDa corresponding to the predicted molecular weight of human CYP1B1. This is the first study to identify CYP1B1 expression in a tumour where it may represent a previously unknown pathway for the metabolism of oestradiol and chemotherapeutic drugs.

Analysis of key cell-cycle checkpoint proteins in colorectal tumours

Aberrations in the components of cell‐cycle checkpoints are a common feature of many tumours and several have been shown to have prognostic significance in colorectal cancer. In this study, seven components of cell‐cycle control [cyclin D1, retinoblastoma (pRb), p21, p27, p16, p53, and proliferating cell nuclear antigen (PCNA)] were examined in a large series of well‐characterized colorectal adenocarcinomas using immunohistochemistry to ascertain co‐regulation and influence on survival. The majority (92%) of the tumours had abnormal staining of ⩾2 cell‐cycle control factors. Expression of cyclin D1 protein was correlated with both p21 (p<0.001) and p27 (p=0.033), suggesting co‐regulation of these proteins in colorectal tumours. Only cyclin D1 (p=0.048) and p53 (p=0.025) were directly associated with PCNA levels, suggesting a more important role in the proliferative capacity of tumour cells. Significant associations between cell cycle‐related proteins and clinicopathological data were observed: cyclin D1 and p53 proteins were correlated with patient age (p=0.042 and p<0.001, respectively) and p53 (p=0.01) and p21 (p=0.024) proteins were associated with tumour site. Expression of cyclin D1 protein was the only protein examined that was related to improved outcome in these patients (p=0.0266), but itwas not an independent predictor of survival. These results suggest that loss of control of cell‐cycle checkpoints is a common occurrence in colorectal tumours and may be an important therapeutic target. Copyright

c-erbB-2 is not a major factor in the development of colorectal cancer

We have investigated c-erbB-2 protein expression in a large cohort of well-characterized colorectal tumours, and in a subset of lymph node metastases. We have also evaluated a Val655Ile single nucleotide polymorphism, which is associated with an increased risk of breast cancer, in a subset of the colorectal cancer patients and in healthy control subjects. Immunohistochemical studies revealed that while 81.8% of tumours expressed c-erbB-2, in the majority of cases equivalent levels of c-erb-B2 were seen in adjacent normal mucosa. Colon tumours were significantly more likely to express c-erbB-2 than rectal tumours (P=0.015). Only 52.4% of the metastases displayed staining patterns concordant with their primary tumour, indicating that determination of c-erbB-2 protein in colorectal tumours cannot predict the status of lymph node metastases. PCR–RFLP analysis of the Val655Ile single nucleotide polymorphism demonstrated that allele frequencies were identical between colorectal cancer patients and a control group of Caucasian subjects (Ile=0.80 and Val=0.20 in each case), indicating that it is not related to the risk of developing colorectal cancer in this population. Furthermore, there was no relationship between c-erbB-2 protein expression and gene polymorphism (P=0.58). In terms of prognosis, no association was seen between either c-erbB-2 protein expression or the presence of the Val allele and patient survival (P>0.05 in each case), suggesting that c-erbB-2 is not a prognostic marker in colorectal cancer.

Colorectal cancer genomics: evidence for multiple genotypes which influence survival.

Colorectal cancer (CRC) is a leading cause of cancer death and the mechanism for variable outcome in this disease is not yet fully understood. It is hypothesized that differences in the genetic make-up of tumours may be partially responsible for the differences observed in survival among same staged individuals for this disease. In this study the tumour genomes of 29 consecutive patients undergoing surgery for Dukes’ C CRC were assessed by comparative genomic hybridization (CGH). In addition, the CGH profiles from the tumours were compared with those from eight colorectal cell lines. Great variation in genetic grade (all detectable aberrations i.e., loss + gain) was observed in 29 Dukes’ C colorectal tumours by CGH (median four aberrations per tumour, range 0–20). Gain was found in 76% and loss in 41% of tumours. The most frequently observed regions of gain were 13q (27.6%), 20q (27.6%), 7p (24.1%), 8q (24.1%), and 1q (20.7%) and loss were 18q (31%), 4q (20.7%), 17p (20.7%), 18p (20.7%), and 15q (20.1%). None of these specific genomic aberrations were associated with patient survival. However, patients with more than two aberrations had a better survival than patients with fewer regions of loss and gain (P = 0.02). CRC cell lines had similar regions of loss or gain as the tumours. However, the frequency of genomic aberrations was much greater in the CRC cell lines. Although genomic change in CRC is relevant to the survival of patients with Dukes’ C CRC, careful analysis is required to identify cell lines which are representative models of CRC genomics.

Therapeutic opportunities from tumour biology in metastatic colon cancer

Tumour metastasis is the major cause of morbidity and mortality from colorectal cancer. While improvements in quality of life and patient survival have been made over the past 10 years, the majority of patients with metastatic colorectal cancer will die from their disease. As knowledge of the biology of colon cancer and its invasion/metastasis programme evolve, this presents new therapeutic opportunities for pharmacological and genetic intervention. This review discusses the current approaches to metastatic colorectal cancer therapy, details genomic and biological variance between primary and metastatic tumours, and highlights approaches for harnessing these differences to improve therapy.