Novel mRNA isoforms and mutations of uridine monophosphate synthetase and 5-fluorouracil resistance in colorectal cancer

The drug fluorouracil (5-FU) is a widely used antimetabolite chemotherapy in the treatment of colorectal cancer. The gene uridine monophosphate synthetase (UMPS) is thought to be primarily responsible for conversion of 5-FU to active anticancer metabolites in tumor cells. Mutation or aberrant expression of UMPS may contribute to 5-FU resistance during treatment. We undertook a characterization of UMPS mRNA isoform expression and sequence variation in 5-FU-resistant cell lines and drug-naive or -exposed primary and metastatic tumors. We observed reciprocal differential expression of two UMPS isoforms in a colorectal cancer cell line with acquired 5-FU resistance relative to the 5-FU-sensitive cell line from which it was derived. A novel isoform arising as a consequence of exon skipping was increased in abundance in resistant cells. The underlying mechanism responsible for this shift in isoform expression was determined to be a heterozygous splice site mutation acquired in the resistant cell line. We developed sequencing and expression assays to specifically detect alternative UMPS isoforms and used these to determine that UMPS was recurrently disrupted by mutations and aberrant splicing in additional 5-FU-resistant colorectal cancer cell lines and colorectal tumors. The observed mutations, aberrant splicing and downregulation of UMPS represent novel mechanisms for acquired 5-FU resistance in colorectal cancer.

Patterns of presentation, referral, and treatment of hepatocellular carcinoma in a pre-sorafenib era: experience of a Canadian provincial cancer agency

BACKGROUND

Systemic treatment options in hepatocellular carcinoma (hcc) are limited. Sorafenib, a multikinase inhibitor, has been shown to improve survival in patients with advanced hcc and adequate hepatic reserve. Currently, the proportion of referred patients with hcc that would be eligible for sorafenib therapy is unclear. We reviewed patterns in the presentation and management of referred patients with hcc at the BC Cancer Agency (bcca) before the availability of sorafenib.

METHODS

Records of patients with hcc referred to the bcca from January 1, 2003, to December 31, 2007, were reviewed. Distributions were analyzed using frequency statistics.

RESULTS

Of 518 patients reviewed, 77% were men and 45% were of Asian ethnicity; median age was 64 years. Histology confirmation was available in only 34% of the patients; 64% had an elevated level of alpha-fetoprotein at diagnosis. The Child-Pugh score at presentation could not be determined in 56%; the most common missing variable was albumin (44%). Among the 226 evaluable patients, the Child-Pugh classification was A in 140 (62%), B in 64 (28%), and C in 22 (10%). Eastern Cooperative Oncology Group performance status was not documented in 40% of patients. The TNM staging was recorded per agency protocol; however, it was incompletely documented in most patients. Distant metastases were recorded in 12% of patients, and 75 patients (15%) underwent hepatic resection before referral. After bcca referral, no further therapy was offered to 287 patients (54%), regional therapy was offered to 170 (33%), and chemotherapy was offered to 67 (13%).

CONCLUSIONS

In this era of targeted therapies, characterizing the proportion of patients with hcc that would be eligible for such therapies is important. In our experience, referred patients are commonly Asian men with an acceptable hepatic reserve by Child-Pugh score, who have been diagnosed by clinical criteria alone. Most patients were offered no further therapy. Moving forward, accurate and systematic documentation of staging, performance status, and Child-Pugh score per the Barcelona Clinic Liver Cancer staging protocol will be imperative to best identify patients who may benefit most from sorafenib or available clinical trials, and to subsequently evaluate the population-based impact of the introduction of such therapies in patients with advanced hcc.

Response to 5-fluorouracil in metastatic extramammary Paget disease of the scrotum presenting as pancytopenia and back pain

Extramammary Paget disease is a rare intraepithelial neoplasm of the vulvar, penoscrotal, or perianal skin. No effective therapies for metastatic disease have been reported, and prognosis for metastatic disease is poor.

Here, we report the case of an Asian man who was initially diagnosed with extramammary Paget disease of the scrotum. Three years later, the patient presented to hospital with pancytopenia and back pain. After an extensive work-up, biopsies of liver and bone marrow revealed adenocarcinoma with signet cells and immunohistochemical staining positive for keratin 7, carcinoembryonic antigen, and prolactininduced protein, but negative for keratin 20, S100, and prostate markers, consistent with his previous biopsyproven Paget disease of the scrotum. The patient was treated with 5-fluorouracil–based therapy in addition to palliative radiotherapy to selected spine levels. A promising palliative response was demonstrated following 5-fluorouracil chemotherapy.

A review of the literature on the pathogenesis, diagnosis, treatment options, and outcomes for metastatic extramammary Paget disease is presented.

Multidisciplinary Canadian consensus recommendations for the management and treatment of hepatocellular carcinoma

Globally, hepatocellular carcinoma (hcc) is the third most common cause of death from cancer, after lung and stomach cancer. The incidence of hcc in Canada is increasing and is expected to continue to increase over the next decade. Given the high mortality rate associated with hcc, steps are required to mitigate the impact of the disease. To address this challenging situation, a panel of 17 hcc experts, representing gastroenterologists, hepatologists, hepatobiliary surgeons, medical oncologists, pathologists, and radiologists from across Canada, convened to provide a framework that, using an evidence-based approach, will assist clinicians in optimizing the management and treatment of hcc. The recommendations, summarized here, were developed based on a rigorous methodology in a pre-specified process that was overseen by the steering committee. Specific topics were identified by the steering committee and delegated to a group of content experts within the expert panel, who then systematically reviewed the literature on that topic and drafted the related content and recommendations. The set of recommendations for each topic were reviewed and assigned a level of evidence and grade according to the levels of evidence set out by the Centre for Evidence-based Medicine, Oxford, United Kingdom. Agreement on the level of evidence for each recommendation was achieved by consensus. Consensus was defined as agreement by a two-thirds majority of the 17 members of the expert panel. Recommendations were subject to iterative review and modification by the expert panel until consensus could be achieved.

Canadian Expert Group consensus recommendations: KRAS testing in colorectal cancer

Monoclonal antibodies against the epidermal growth factor receptor (anti-egfr) when used in the treatment of metastatic colorectal cancer are associated with improved survival. Patients whose tumours harbor a KRAS mutation in codon 12 or 13 have been shown not to benefit from anti-egfr antibodies. The importance of KRAS mutation status in the management of patients with metastatic colorectal cancer has led to the elaboration of Canadian consensus recommendations on KRAS testing, with the aim of standardizing practice across Canada and reconciling testing access with the clinical demand for testing. The present guidelines were developed at a Canadian consensus meeting held in Montreal in April 2010. The best available evidence and expertise were used to develop recommendations for various aspects of KRAS testing, including indications and timing for testing, sample requirements, recommendations for reporting requirements, and acceptable turnaround times.

Electronic portal imaging vs kilovoltage imaging in fiducial marker image-guided radiotherapy for prostate cancer: an analysis of set-up uncertainties

OBJECTIVES

The purpose of this study was to compare interfraction prostate displacement data between electronic portal imaging (EPI) and kilovoltage imaging (KVI) treatment units and discuss the impact of any difference on margin calculations for prostate cancer image-guided radiotherapy (IGRT).

METHODS

Prostate interfraction displacement data was collected prospectively for the first 4 fractions in 333 patients treated with IGRT with daily pre-treatment EPI or KVI orthogonal imaging. Displacement was recorded in the anteroposterior (AP), left-right (LR) and superoinferior (SI) directions. The proportion of displacement <3 mm and the difference in median absolute displacements were calculated in all directions.

RESULTS

1088 image pairs were analysed in total, 448 by EPI and 640 by KVI. There were 23% (95% confidence interval [CI] 18-28%) more displacements under 3 mm for EPI than for KVI in the AP direction, 14% (95% CI 10-19%) more in the LR direction and 10% (95% CI 5-15%) more in the SI direction. The differences in absolute median displacement (KVI>EPI) were AP 1 mm, LR 1 mm and SI 0.5 mm. Wilcoxon rank-sum test showed that distributions were significantly different for all three dimensions (p<0.0001 for AP and LR and p=0.02 for SI).

CONCLUSION

EPI has a statistically significant smaller set-up error distribution than KVI. We would expect that, because fiducial marker imaging is less clear for EPI, the clinical target volume to planning target volume margin would be greater when using IGRT; however, relying wholly on displacement data gives the opposite result. We postulate that this is owing to observer bias, which is not accounted for in margin calculation formulas.

Progression-free survival as a primary endpoint in clinical trials of metastatic colorectal cancer

In recent years, significant advances have been made in the management of metastatic colorectal cancer. Traditionally, an improvement in overall survival has been considered the "gold standard"-the most convincing measure of efficacy. However, overall survival requires larger patient numbers and longer follow-up and may often be confounded by other factors, including subsequent therapies and crossover. Given the number of active therapies for potential investigation, demand for rapid evaluation and early availability of new therapies is growing. Progression-free survival is regarded as an important measure of treatment benefit and, compared with overall survival, can be evaluated earlier, with fewer patients and no confounding by subsequent lines of therapy. The present paper reviews the advantages, limitations, and relevance of progression-free survival as a primary endpoint in randomized trials of metastatic colorectal cancer.

Progression-Free Survival as a Primary Endpoint in Clinical Trials of Metastatic Colorectal Cancer

In recent years, significant advances have been made in the management of metastatic colorectal cancer. Traditionally, an improvement in overall survival has been considered the “gold standard”—the most convincing measure of efficacy. However, overall survival requires larger patient numbers and longer follow-up and may often be confounded by other factors, including subsequent therapies and crossover. Given the number of active therapies for potential investigation, demand for rapid evaluation and early availability of new therapies is growing. Progression-free survival is regarded as an important measure of treatment benefit and, compared with overall survival, can be evaluated earlier, with fewer patients and no confounding by subsequent lines of therapy. The present paper reviews the advantages, limitations, and relevance of progression-free survival as a primary endpoint in randomized trials of metastatic colorectal cancer.

Subchronic Oral Toxicity Study of Furan in B6C3F1 Mice

Furan is a heterocyclic organic compound formed during heat treatment for processing and preservation of various types of food. Rodent studies have previously shown that furan is a hepatocarcinogen. Those studies were conducted over a high dose range, which induced tumors at nearly 100% incidence at all doses. This ninety-day gavage study in mice was conducted to extend the dose to a lower range (0.0, 0.03, 0.12, 0.5, 2.0, and 8.0 mg/kg body weight [bw] per day) to identify a no-observed adverse effect level for hepatotoxicity and to characterize non-neoplastic effects, including those affecting clinical biochemistry, hematology, tissue morphology, and histopathology. The liver was the primary target organ with dose-dependent toxicity. Liver weights were increased at the 8.0 mg/kg bw dose in females only. Levels of the serum enzyme alanine transaminase, representative of liver damage, were increased three-fold at the highest dose. Histological changes in the liver were observed at 2.0 and 8.0 mg/kg bw in both sexes. Although clinical parameters were also altered for the kidney, these differences were not accompanied by histological changes. Based on these clinical biochemical and histological changes, a no-observed adverse effect level of 0.12 mg/kg bw per day of furan in mice is suggested.

Lip, a human gene detected by transfection of DNA from a human liposarcoma encodes a protein with homology to regulators of small g proteins

Purpose/Method. Transfection experiments have been used to identify activated oncogenes in a wide variety of tumour types. Here we describe the use of transfection experiments utilizing DNA from a human pleomorphic liposarcoma to identify a novel gene, designated lip which maps to chromosome 19.Results. lip was expressed in all sarcoma cell lines examined and a wide variety of normal tissues. Sequencing of cDNAs prepared from transcripts of the normal lip gene indicates that lip is predicted to encode a 966 amino acid protein with a region of homology to proteins such as vav, dbl, lbc and ect-2 which act as GDP-GTP exchange factors for the RAS superfamily of small GTP-binding proteins, and the N-terminal 830 amino acids are identical to the recently identified gene p115-RhoGEF, an exchange factor for RHOA. In transfectants, lip has undergone a rearrangement which results in C-terminal truncation of the predicted LIP protein. However, we failed to detect this alteration in the primary liposarcoma used in the original transfection experiments, or in other sarcoma specimens examined.Discussion. When considered together, these observations suggest that transforming lip sequences represent an alternatively spliced form of p115-RhoGEF that is activated for transformation by C-terminal truncation during transfection, and is not widely involved in sarcoma development.

Amplification and Over-Expression of the MDM2 Gene in Human Soft Tissue Tumours

Purpose. Amplification of genetic sequences on chromosome 12q13 is frequently found in soft tissue tumours. However, for the MDM2 gene, over-expression of the MDM2 protein has not always been shown to accompany gene amplification, raising the possibility that amplification of genetic sequences targets alternative genes on chromosome 12q13 for over-expression. To investigate this discrepancy, we have examined 129 soft tissue tumours for amplification of the MDM2 gene using Southern analysis, and 39 of these tumours were also examined by immunohistochemical staining for MDM2 over-expression.Results. Gene amplification was identified in 14/114 (12.3%) of the malignant tumours, but was not identified in any of the benign tumours; 21/39 (54%) of the malignant tumours also demonstrated MDM2 over-expression. Within this group the MDM2 gene was over-expressed in every tumour in which the gene amplification was found, and over-expression in the absence of gene amplification was also found in an additional 10 tumours.Discussion. These data demonstrate a clear correlation between the presence of MDM2 amplification and MDM2 over-expression, and provide persuasive evidence therefore that the amplification of genetic sequences on chromosome 12q13 in soft tissue sarcomas targets the MDM2 gene for over-expression. These data also indicate that alternative mechanisms may contribute to MDM2 over-expression within some tumours.

Consensus recommendations for the use of anti-egfr therapies in metastatic colorectal cancer

In January 2010, a panel of Canadian oncologists with particular expertise in colorectal cancer (crc) gathered to develop a consensus guideline on the use of therapies against the epidermal growth factor receptor (egfr) in the management of metastatic crc (mcrc). This paper uses a case-based approach to summarize the consensus recommendations developed during that meeting.These are the consensus recommendations:Testing for the KRAS status of the tumour should be performed as soon as an egfr inhibitor is being considered as an option for treatment.Anti-egfr therapies are not recommended for the treatment of patients with tumours showing mutated KRAS status.For a patient with wild-type KRAS and an Eastern Cooperative Oncology Group status of 0-2, whose mcrc has previously been treated with a fluoropyrimidine, irinotecan, and oxaliplatin, switching to an egfr inhibitor is a recommended strategy.Cetuximab, cetuximab plus irinotecan, and panitumumab are all options for third-line therapy in patients with wild-type KRAS, provided that tolerability is acceptable.

Evaluation and optimization of the administration of a selectively replicating herpes simplex viral vector to the brain by convection-enhanced delivery

The direct intraparenchymal administration of oncolytic viral vectors by convection-enhanced delivery (CED) represents a promising new treatment strategy for malignant gliomas. However, there is no evidence to suggest that oncolytic viruses as large as herpes simplex virus-1 (HSV-1) can be administered by CED, as this has not been systematically examined in an animal model. In this study, the administration of a herpes simplex viral vector, HSV1, has been evaluated in detail in the gray and white matter of both rat and pig models, using high flow-rate infusions, co-infusing heparin or preinfusing the tissue with an isotonic albumin solution. Rat HSV-1 infusions at both slow (0.5 μl min(-1)) and high infusion rates (2.5 μl min(-1)) led to extensive tissue damage and negligible cell transduction. Co-infusion with heparin led to extensive hemorrhage. Preinfusion of tissue with an isotonic albumin solution facilitated widespread vector distribution and cell transduction in white matter only. Using this approach in pig brain led to widespread vector distribution with extensive transduction of astrocytes and activated microglia. In rat brain, enhanced green fluorescent protein expression peaked 48 h after vector administration and was associated with a vigorous immune response. These findings indicate that direct infusions of HSV-1-based viral vectors into the brain lead to minimal vector distribution, negligible cell transduction and extensive damage. Tissue preinfusion with an isotonic solution prior to vector administration represents an effective technique for achieving widespread HSV-1 distribution.