The results of colorectal cancer treatment by p53 status: treatment-specific overview

Precision medicine for adjuvant chemotherapy of resected colorectal cancer

Colorectal cancer (CRC) is the most common cancer and the second leading cause of cancer death in Japan. Surgical resection is the only curative option for localized disease. However, undetectable micrometastases remaining after curative surgery may cause disease recurrence. Adjuvant chemotherapy aims to eradicate these micrometastases to improve the cure rate. Unfortunately, few reliable prognostic and predictive markers are available that identify patients at high risk for CRC during early-stage disease. However, promising biomarkers may become available in the near future. Such biomarkers provide information for stratifying a patient's risk and for selecting the optimal treatment. Here, we provide an overview of current relevant prognostic and predictive biomarkers applicable to adjuvant treatment of early-stage CRC and focus on the future of this field.

Landscape of somatic single nucleotide variants and indels in colorectal cancer and impact on survival

Colorectal cancer (CRC) is a biologically heterogeneous disease. To characterize its mutational profile, we conduct targeted sequencing of 205 genes for 2,105 CRC cases with survival data. Our data shows several findings in addition to enhancing the existing knowledge of CRC. We identify PRKCI, SPZ1, MUTYH, MAP2K4, FETUB, and TGFBR2 as additional genes significantly mutated in CRC. We find that among hypermutated tumors, an increased mutation burden is associated with improved CRC-specific survival (HR = 0.42, 95% CI: 0.21–0.82). Mutations in TP53 are associated with poorer CRC-specific survival, which is most pronounced in cases carrying TP53 mutations with predicted 0% transcriptional activity (HR = 1.53, 95% CI: 1.21–1.94). Furthermore, we observe differences in mutational frequency of several genes and pathways by tumor location, stage, and sex. Overall, this large study provides deep insights into somatic mutations in CRC, and their potential relationships with survival and tumor features.

Large scale sequencing study is of paramount importance to unravel the heterogeneity of colorectal cancer. Here, the authors sequenced 205 cancer genes in more than 2000 tumours and identified additional mutated driver genes, determined that mutational burden and specific mutations in TP53 are associated with survival odds.

Novel biomarkers for the diagnosis and prognosis of colorectal cancer

Colorectal cancer (CRC) is among the most common malignancies and remains a major cause of cancer-related death worldwide. Despite recent advances in surgical and multimodal therapies, the overall survival of advanced CRC patients remains very low. Cancer progression, including invasion and metastasis, is a major cause of death among CRC patients. The underlying mechanisms of action resulting in cancer progression are beginning to unravel. The reported molecular and biochemical mechanisms that might contribute to the phenotypic changes in favor of carcinogenesis include apoptosis inhibition, enhanced tumor cell proliferation, increased invasiveness, cell adhesion perturbations, angiogenesis promotion, and immune surveillance inhibition. These events may contribute to the development and progression of cancer. A biomarker is a molecule that can be detected in tissue, blood, or stool samples to allow the identification of pathological conditions such as cancer. Thus, it would be beneficial to identify reliable and practical molecular biomarkers that aid in the diagnostic and therapeutic processes of CRC. Recent research has targeted the development of biomarkers that aid in the early diagnosis and prognostic stratification of CRC. Despite that, the identification of diagnostic, prognostic, and/or predictive biomarkers remains challenging, and previously identified biomarkers might be insufficient to be clinically applicable or offer high patient acceptability. Here, we discuss recent advances in the development of molecular biomarkers for their potential usefulness in early and less-invasive diagnosis, treatment, and follow-up of CRC.

TAT-RasGAP317-326 Enhances Radiosensitivity of Human Carcinoma Cell Lines In Vitro and In Vivo through Promotion of Delayed Mitotic Cell Death

The synthetic peptide TAT-RasGAP_317-326 has been shown to potentiate the efficacy of anti-cancer drugs. In this study, we explored the action of TAT-RasGAP_317-326 when combined with radiation by investigating its radiosensitizing activity in vitro and in vivo. To investigate the modulation of intrinsic radiosensitivity induced by TAT-RasGAP_317-326, clonogenic assays were performed using four human cancer cell lines, HCT116 p53^+/+ (ATCC: CCL-247), HCT116 p53^-/-, PANC-1 (ATCC: CRL-1469) and HeLa (ATCC: CCL-2), as well as one nontumor cell line, HaCaT (CLS: 300493). Next, to investigate tumor growth delay after irradiation, HCT116 cell lines were selected and xenografted onto nude mice that were then treated with TAT-RasGAP_317-326 alone or in combination with radiation or cisplatin. Afterwards, cell cycle and death modulation were investigated by quantification of micronuclei and apoptosis-related protein array. TAT-RasGAP_317-326 radiosensitized all four human carcinoma cell lines tested but displayed no effect on normal cells. It also displayed no effect when administered as monotherapy. This radiosensitizing effect was confirmed in vivo in both p53-positive and p53-negative HCT116 xenografts. TAT-RasGAP_317-326 combined with radiation enhanced the number of cells in S phase and subsequently delayed cell death, but had almost no effect on major apoptosis-related proteins. TAT-RasGAP_317-326 is a radiosensitizing agent that acts on carcinoma cells and its radiosensitizing effect might be mediated, at least in part, by the enhancement of mitotic cell death.

TP53 Mutational Status and Prediction of Benefit from Adjuvant 5-Fluorouracil in Stage III Colon Cancer Patients

We investigated the hypothesis that the varying treatment efficacy of adjuvant 5-fluorouracil (5FU) in stage III colon cancer is linked to the TP53 mutational status. ABCSG-90 was a prospective randomized trial in which effect of adjuvant 5FU was studied in stage III colon cancer patients. Tumor material of 70% of these patients (389/572) was available for analysis of the biomarker TP53 using a TP53-gene-specific Sanger sequencing protocol. Median follow-up was 88 months. TP53 mutation frequency was 33%. A significant interaction between TP53 status, outcomes and nodal category was found (P = 0.0095). In the N1 category, TP53 wildtype patients had significantly better overall survival than TP53 mutated (81.0% vs. 62.0% overall survival at 5 years; HR = 2.131; 95% CI: 1.344-3.378; P = 0.0010). In the N2 category, the TP53 status did not affect survival (P = 0.4992). In TP53 wildtype patients, the prognostic significance of N category was significantly enhanced (P = 0.0002). In TP53 mutated patients, survival curves of N1 and N2 patients overlapped and nodal category was no longer prognostic. The biomarker TP53 independently predicted effect of adjuvant 5FU in N1 colon cancer patients. TP53 was not predictive in N2 patients, in whom 5FU is known to have no effect.

Assessing the TP53 marker type in patients treated with or without neoadjuvant chemotherapy for resectable colorectal liver metastases: a p53 Research Group study

The type of a biomarker - whether it is prognostic or predictive - is frequently not known, although such information is crucial for assessing the clinical value of a marker. In order to evaluate the type of marker TP53 is, we identified a cohort of 76 patients with colorectal liver metastases (CLM), homogeneously staged as resectable, who had been treated either with or without fluorouracil-based neoadjuvant chemotherapy. The TP53 genotype was assessed retrospectively from paraffin-embedded, diagnostic tumour biopsies using a standardised, p53 gene-specific sequencing protocol (mark53(®) kit). The overall median survival was 44.2 months, and the overall TP53 mutation frequency was 55%. A significant interaction was observed between chemotherapy and TP53 status (P = 0.045). To illustrate this effect, the 51 patients with and the 25 patients without neoadjuvant chemotherapy were described separately. In patients with neoadjuvant chemotherapy, mutated TP53 was significantly associated with poor survival (P = 0.0025), resulting in five-year survival rates of 22%, compared to 60% in patients with normal TP53. The hazard ratio was 3.12 (95% confidence intervals (CI): 1.46-6.95) to the disadvantage of TP53-mutated patients and 5.49 (P = 0.0001; 95% CI: 2.28-13.24) after adjustment for known prognostic factors. In patients treated with surgery alone, a mutated TP53 did not have a negative effect on survival (P = 0.54). A mutated TP53 status independently predicted survival disadvantage in CLM patients in the presence, but not in the absence, of neoadjuvant chemotherapy. Our data suggest that TP53 might be a pure predictive marker.

Mutant p53 and the response to chemotherapy and radiation

In addition to playing roles in the genesis and progression of cancer, mutant p53 also appears to play a significant role in the response to cancer therapy. In response to chemotherapy and radiation, two mainstays of cancer treatment, most cancer cells harboring p53 mutations show a reduced sensitivity compared to cells lacking p53 or those with wild type p53. However, there are also many instances where mutant p53 has shown no effect or enhances cellular sensitivity to chemotherapy and radiation. Similar to the in vitro cellular studies, the majority of clinical studies show a correlation between the presence of mutant p53 in patient tumors and adverse outcomes following treatment with chemotherapy agents or radiation in comparison to tumors with wild-type p53. However, it still remains unclear whether the presence of mutant p53 in tumors can serve as a reliable prognostic factor and aid in treatment planning. Thus, as genomic analysis of patient tumors becomes more cost effective, the role of mutant p53 in tumor responses from cancer therapy ultimately needs to be addressed. This chapter will discuss current mechanisms of how p53 mutations affect cellular responses to chemotherapy and radiation and discuss patient outcomes based on p53 status.

The prognostic value of c-Kit, K-ras codon 12, and p53 codon 72 mutations in Egyptian patients with stage II colorectal cancer

BACKGROUND

The prognosis for patients with colorectal cancer (CRC) depends mainly on standard clinicopathologic factors. However, patients with similar disease characteristics exhibit various outcomes, especially in stage II. Therefore, the identification of molecular prognostic markers is needed to predict patient outcomes.

METHODS

The authors assessed the prognostic value of c-Kit (also called cluster of differentiation 117 [CD117] or KIT), cyclooxygenase-2 (COX-2), tumor protein 53 (p53), and Kirsten rat sarcoma viral oncogene homolog (K-ras) aberrations in 90 patients with stage II CRC using immunohistochemistry and molecular techniques. The results were correlated with standard clinicopathologic prognostic factors, overall survival (OS), and disease-free survival (DFS).

RESULTS

COX2 and c-Kit overexpression was detected in 54.6% and 59.3% of patients, respectively. Overexpression of p53 was detected in 47 patients, including 29 who had mutations, and a unique mutation pattern was detected with 3 hotspots at codons 72, 245, and 273. Overexpression of ras was detected in 44 patients, including 37 who had mutations. On multivariate analysis, c-Kit overexpression, p53 codon 72 mutations, perforation, and performance status were independent prognostic factors for DFS (P=.054, P=.015, P<.0001, and P=.043, respectively); whereas codon 12 K-ras mutation, performance status, and perforation were independent prognostic factors for OS (P=.033, P=.006, and P<.0001, respectively).

CONCLUSIONS

The current results provide evidence for the prognostic value of c-Kit overexpression in patients with stage II CRC. The high p53 mutation rate and the unique hotspot in codon 72 have not been reported previously in CRC. This may be related to environmental or racial features that are unique to the studied population.

Adjuvant colon cancer chemotherapy: where we are and where we'll go

Many patients with early-stage colon cancer are cured with surgery alone, even if the standard of care remains an uniform approach to adjuvant chemotherapy based primarily on tumour stage. Consequently, it is important to individualize decision-making in this subset of patients with the aim to identify potential prognostic and predictive markers in colon cancer. While 5-fluorouracil, leucovorin, and oxaliplatin are widely known as gold treatment in the post-operative of stage III, well-validated molecular markers might help define which patients with stage II disease are likely to benefit from adjuvant therapy as well. Herein we review the use of adjuvant chemotherapy in colon cancer and analyzed the date on the clinical development of molecular markers to individualize another therapeutic approach in colon cancer.

Prognostic and predictive biomarkers in resected colon cancer: current status and future perspectives for integrating genomics into biomarker discovery

The number of agents that are potentially effective in the adjuvant treatment of locally advanced resectable colon cancer is increasing. Consequently, it is important to ascertain which subgroups of patients will benefit from a specific treatment. Despite more than two decades of research into the molecular genetics of colon cancer, there is a lack of prognostic and predictive molecular biomarkers with proven utility in this setting. A secondary objective of the Pan European Trials in Adjuvant Colon Cancer-3 trial, which compared irinotecan in combination with 5-fluorouracil and leucovorin in the postoperative treatment of stage III and stage II colon cancer patients, was to undertake a translational research study to assess a panel of putative prognostic and predictive markers in a large colon cancer patient cohort. The Cancer and Leukemia Group B 89803 trial, in a similar design, also investigated the use of prognostic and predictive biomarkers in this setting. In this article, the authors, who are coinvestigators from these trials and performed similar investigations of biomarker discovery in the adjuvant treatment of colon cancer, review the current status of biomarker research in this field, drawing on their experiences and considering future strategies for biomarker discovery in the postgenomic era.

Clinical impact of microsatellite instability in colon cancer following adjuvant FOLFOX therapy

PURPOSE

Colon cancer with DNA mismatch repair (MMR) defects reveals indistinguishable clinical and pathologic aspects, including better prognosis and reduced response to 5-fluorouracil (5-FU)-based chemotherapy. There has been no consensus for p53 as a prognostic marker in colorectal cancer. This study investigated the clinical implication of MSI-H/MMR-D and p53 expression in R0-resected colon cancer patients who received adjuvant oxaliplatin/5-FU/leucovorin (FOLFOX) therapy.

EXPERIMENTAL DESIGN

We analyzed 135 patients, who had been treated by adjuvant chemotherapy containing 5-FU and oxaliplatin (FOLFOX) after curative resection (R0) for colon adenocarcinoma between May 2004 and November 2007. Tumor expression of the MMR proteins, MLH1 and MSH2, was detected by immunohistochemistry (IHC) in surgically resected tumor specimens. MSI was analyzed by polymerase chain reaction (PCR) amplification using fluorescent dye-labeled primers specific for microsatellite loci. Tumors with MMR defects were defined as those demonstrating loss of MMR protein expression (MMR-D) and/or microsatellite instability high (MSI-H) genotype. Expression patterns of p53 were determined in a semiquantitative manner by light microscopy.

RESULTS

There were 13 (9.6%) patients with stage II, 108 (80%) with stage III, and 14 (10.4%) with stage IV. Fourteen patients with stage IV (10.3%) had metastases to liver only, all of whom underwent complete metastasectomy for liver metastases. In total, 134 tumor specimens were genotyped, 115 specimens were tested by IHC and 113 cases had both genotyping and IHC results available for analysis. Genotyping results demonstrated that 12 (9.0%) cases were MSI-H and 122 (91.0%) were MSI-L/S. By IHC, 11 (9.6%) patients were MMR-D and 104 (90.4%) were MMR-I. The methods were in agreement in 108 patients (94.7%). We assessed 114 patients for p53 expression by immunostaining. MMR status was not significantly associated with DFS (P = 0.56) or OS (P = 0.61) in patients with colon cancer (n = 135) receiving adjuvant FOLFOX. According to p53 status, there was also no significant difference for DFS (P = 0.11) and OS (P = 0.94). For patients with genotyping/IHC agreement (n = 108), there was no difference in DFS (P = 0.57) and OS (P = 0.98) between patients with MSI-H/MMR-D and MSI-L/S/MMR-I tumors.

CONCLUSION

The MMR status or p53 positivity was not significantly associated with outcomes to FOLFOX as adjuvant chemotherapy in colon cancer patients with R0 resection. Adding oxaliplatin in adjuvant chemotherapy may overcome negative impact of 5-FU on colon cancers with MSI-H/MMR-D.

A novel A33 promoter-based conditionally replicative adenovirus suppresses tumor growth and eradicates hepatic metastases in human colon cancer models

PURPOSE

A33 antigen is a membrane-bound protein expressed in intestinal epithelium that is overexpressed in 95% of primary and metastatic colorectal carcinomas but is absent in most epithelial tissues and tumor types. We hypothesized that A33 promoter might be useful in the design of a conditionally replicative adenovirus for the treatment of colorectal cancer (CRC).

EXPERIMENTAL DESIGN

We cloned an A33 promoter fragment (A33Pr) that extends from -105 to +307 bp. Using luciferase activity as a reporter gene, we showed that A33Pr was active in CRC cell lines. We next constructed a conditionally replicative adenovirus named AV22EL where E1A was placed under the control of A33Pr. The tumor-specific oncolytic effect of AV22EL was investigated both in vitro and in vivo.

RESULTS

AV22EL induced specific in vitro lysis of human CRC cell lines that expressed A33 and have negligible lytic capacity on cells that lacked or had minimal A33 expression, including normal human colonic cells. In vivo, a marked reduction of tumor growth and increased long-term survival rates were observed in nude mice xenografted with s.c. CRC tumors. Combination with 5-fluorouracil induced an additive effect in vitro with no toxic effects in vivo. Remarkably, AV22EL completely eliminated established hepatic metastases in >90% of mice and restored hepatic function according to biochemical parameters. Its systemic administration induced E1A expression only in the hepatic metastasis but not in normal organs.

CONCLUSIONS

These data show that AV22EL is a stringently regulated and potent oncolytic agent for the treatment of CRC.

Tumor associated stromal cells play a critical role on the outcome of the oncolytic efficacy of conditionally replicative adenoviruses

The clinical efficacy of conditionally replicative oncolytic adenoviruses (CRAd) is still limited by the inefficient infection of the tumor mass. Since tumor growth is essentially the result of a continuous cross-talk between malignant and tumor-associated stromal cells, targeting both cell compartments may profoundly influence viral efficacy. Therefore, we developed SPARC promoter-based CRAds since the SPARC gene is expressed both in malignant cells and in tumor-associated stromal cells. These CRAds, expressing or not the Herpes Simplex thymidine kinase gene (Ad-F512 and Ad(I)-F512-TK, respectively) exerted a lytic effect on a panel of human melanoma cells expressing SPARC; but they were completely attenuated in normal cells of different origins, including fresh melanocytes, regardless of whether cells expressed or not SPARC. Interestingly, both CRAds displayed cytotoxic activity on SPARC positive-transformed human microendothelial HMEC-1 cells and WI-38 fetal fibroblasts. Both CRAds were therapeutically effective on SPARC positive-human melanoma tumors growing in nude mice but exhibited restricted efficacy in the presence of co-administered HMEC-1 or WI-38 cells. Conversely, co-administration of HMEC-1 cells enhanced the oncolytic efficacy of Ad(I)-F512-TK on SPARC-negative MIA PaCa-2 pancreatic cancer cells in vivo. Moreover, conditioned media produced by stromal cells pre-infected with the CRAds enhanced the in vitro viral oncolytic activity on pancreatic cancer cells, but not on melanoma cells. The whole data indicate that stromal cells might play an important role on the outcome of the oncolytic efficacy of conditionally replicative adenoviruses.

Can the clinical outcome in stage II colon carcinomas be predicted by determination of molecular marker expression?

BACKGROUND

Conventional staging procedures are often unable to precisely predict prognosis in colon cancer (CC). In this study, we set out to investigate the possible role of molecular/structural indicators involved in cell cycle regulation (Ki-67, p53), apoptosis (p53 and bcl-2) and tumour neoangiogenesis (anti-VIII factor) in predicting tumour behaviour and clinical outcome in stage II CC patients.

EXPERIMENTAL DESIGN

Analysis of the above indicators was performed by immunohistochemistry on 162 CC patient samples with curative intention surgery. Clinicopathological data included tumour grade, vascular and nervous invasion, production of mucin, lymphatic permeation and carcinoembryonic antigen levels.

RESULTS

p53 protein was overexpressed in 58%, bcl-2 overexpression in 21.5%, Ki-67 in 60.1% and anti-VIII factor stained positive in 40.16% of the cases. Multiple regression analysis showed that some molecular markers were correlated. A significant relationship was seen between p53 and Ki-67, and bcl-2 and p53, but there was no correlation between bcl2 and Ki- 67 overexpression. Stepwise regression selected Ki-67 and anti-VIII factor as the best combination of variables capable of predicting both disease-specific and diseasefree survival.

CONCLUSIONS

Only Ki-67 and anti-VIII factor were shown to be useful for the prediction of outcome and recurrence rate in curatively treated CC patients. In conjunction with clinical and pathological staging, they may provide a stronger indication of clinical outcome than staging alone and help better select therapeutic options in CC patients.

A prospective, blinded analysis of thymidylate synthase and p53 expression as prognostic markers in the adjuvant treatment of colorectal cancer

BACKGROUND

Despite previous studies, uncertainty has persisted about the role of thymidylate synthase (TS) and p53 status as markers of prognosis in colorectal cancer (CRC).

PATIENTS AND METHODS

A total of 967 patients accrued to a large adjuvant trial in CRC were included in a prospectively planned molecular substudy, and of them, 59% had rectal cancer and about 90% received adjuvant chemotherapy (either systemically or randomly allocated to intraportal 5-fluorouracil infusion or both). TS and p53 status were determined, blinded to any clinical data, by immunohistochemistry using a validated polyclonal antibody or the DO-7 clone, respectively, and their relationships with overall survival were examined.

RESULTS

High TS expression was observed in 58% and overexpression of p53 in 60% of tumours. TS expression correlated with tumour stage, and p53 overexpression, with rectal cancers. There was no evidence that either marker was significantly associated with survival by either univariate (TS hazard ratio (HR) = 0.94, 95% CI 0.76-1.18 and P = 0.6 and p53 HR = 0.98, 95% CI 0.78-1.23 and P = 0.9) or multivariate analyses (TS HR = 0.99, 95% CI 0.79-1.25 and P = 0.9 and p53 HR = 0.98, 95% CI 0.78-1.23 and P = 0.8).

CONCLUSIONS

Neither TS nor p53 expression has significant prognostic value in the adjuvant setting of CRC.

Molecular prognostic markers in resectable colorectal liver metastases: a systematic review

BACKGROUND

Determination of prognosis in patients with resectable colorectal liver metastases (CLM) is desirable in order to improve case selection for surgery and tailor adjuvant treatment according to individual recurrence risk. Conventional clinicopathological factors lack the sensitivity to accurately achieve this goal. Consideration of tumour biology and the identification of molecular prognostic markers may allow more accurate risk stratification.

METHOD

This systematic review examines evidence from published manuscripts looking at molecular markers in resectable colorectal liver metastases and their correlation with disease recurrence and survival following hepatectomy.

RESULTS

Studies have yielded promising results in the search for prognostic molecular markers of CLM. Molecular biomarkers from varied aspects of tumour biology have been examined and a number of these, including proliferation indices, telomerase, thymidylate synthase, microvessel density and thrombospondin-1 appear to have prognostic utility in this context. Validation of other markers, notably p53, has been limited by a failure of methodologies to account for their biological complexity.

CONCLUSIONS

A biomarker-based approach may yield significant benefits through informed treatment of resectable metastatic colorectal malignancy. Standardised retrospective analyses are necessary to confirm preliminary findings and identify existing and novel markers for inclusion into prospective studies. Assessment and verification of multiple molecular markers in this manner may allow molecular profiling of metastases and tailoring of therapy according to the biological aggressiveness of individual tumours. The advent of genomic- and proteomic-based technologies will allow the simultaneous analysis of multiple molecular markers and the derivation of disease profiles associated with disease recurrence and poor survival.

Inter-relationship between microsatellite instability, thymidylate synthase expression, and p53 status in colorectal cancer: implications for chemoresistance

Background

Studies indicate that thymidylate synthase (TS) expression, p53 and mismatch repair status have potential to influence colorectal cancer (CRC) outcome. There is, however, little data on the inter-relationship between these three markers. We sought to investigate whether relationships exist between these markers that might contribute to CRC phenotypes.

Methods

Four hundred and forty-one stage I-III CRCs were investigated. p53 status and TS expression were assessed by standard immunohistochemistry methods. Mismatch repair status was determined by assessment of microsatellite instability (MSI) using radiolabelled microsatellite genotyping.

Results

244 tumours (55%) over-expressed p53, and 259 (58%) expressed high TS levels. 65 tumours (15%) had MSI. A significant relationship between p53 over-expression and high TS expression was observed (p = 0.01). This was independent of MSI status. A highly significant inverse relationship between MSI and p53 status was observed (p = 0.001). No relationship was seen between MSI status and TS expression (p = 0.59).

Conclusion

Relationships exist between p53 status and TS expression, and MSI and p53 status. These inter-relationships may contribute to the clinical phenotype of CRCs associated with each of the molecular markers. High TS expression is unlikely to account for the clinical behaviour of CRCs with MSI.

P53 abnormalities and outcomes in colorectal cancer: a systematic review

We performed a systematic review of studies that investigated the effect of abnormalities of the tumour suppressor gene p53 upon prognosis in patients with colorectal cancer. The methods used to assess p53 status were immunohistochemistry (IHC), indicating abnormal accumulation of p53, and sequence analysis, indicating presence of p53 mutations (mut). We identified 168 reports, with 241 comparisons of relevant end points and survival data on 18 766 patients. We found evidence of both publication bias and heterogeneity of results. Our analysis was hampered by variability in both the assessment of p53 status and the reporting of results. We used a trim and fill method to correct for publication bias and minimised heterogeneity by using well-defined clinical subgroups for the assessment of outcomes. Overall, patients with abnormal p53 were at increased risk of death: relative risk (RR) with IHC 1.32 (95% confidence interval (c.i.) 1.23–1.42) and with mutation analysis 1.31 (95% c.i. 1.19–1.45). The adverse impact of abnormal p53 was greater in patients with lower baseline risk of dying: good prognosis RR (mut) 1.63 (95% c.i. 1.40–1.90) and poor prognosis RR (mut) 1.04 (95% c.i. 0.91–1.19). We found no effect of abnormal p53 on outcome in patients treated with chemotherapy. Abnormal p53 was associated with failure of response to radiotherapy in patients with rectal cancer: RR (mut) 1.49 (95% c.i. 1.25–1.77).

Tumoral drug metabolism: overview and its implications for cancer therapy

Drug-metabolizing enzymes (DME) in tumors are capable of biotransforming a variety of xenobiotics, including antineoplastics, resulting in either their activation or detoxification. Many studies have reported the presence of DME in tumors; however, heterogeneous detection methodology and patient cohorts have not generated consistent, firm data. Nevertheless, various gene therapy approaches and oral prodrugs have been devised, taking advantage of tumoral DME. With the need to target and individualize anticancer therapies, tumoral processes such as drug metabolism must be considered as both a potential mechanism of resistance to therapy and a potential means of achieving optimal therapy. This review discusses cytotoxic drug metabolism by tumors, through addressing the classes of the individual DME, their relevant substrates, and their distribution in specific malignancies. The limitations of preclinical models relative to the clinical setting and lack of data on the changes of DME with disease progression and host response will be discussed. The therapeutic implications of tumoral drug metabolism will be addressed-in particular, the role of DME in predicting therapeutic response, the activation of prodrugs, and the potential for modulation of their activity for gain are considered, with relevant clinical examples. The contribution of tumoral drug metabolism to cancer therapy can only be truly ascertained through large-scale prospective studies and supported by new technologies for tumor sampling and genetic analysis such as microarrays. Only then can efforts be concentrated in the design of better prodrugs or combination therapy to improve drug efficacy and individualize therapy.

Ewing Sarcomas Withp53Mutation orp16/p14ARFHomozygous Deletion: A Highly Lethal Subset Associated With Poor Chemoresponse

Purpose

EWS-FLI1 fusion type, p53 mutation, and homozygous deletion of p16/p14ARF have each been shown to be prognostically significant in Ewing sarcoma (ES). We provide the first combined prognostic analysis of these three molecular parameters in ES.

Patients and Methods

We studied 60 patients with ES (stage: localized in 54, metastatic in six). All cases were confirmed to contain the EWS-FLI1 (29 type 1, 12 type 2, 14 other types) or EWS-ERG fusions (five cases). Homozygous deletion of p16/p14ARF, and p53 mutations were determined by fluorescent in situ hybridization and Affymetrix (Santa Clara, CA) p53 GeneChip microarray hybridization, respectively.

Results

Eight cases (13.3%) contained point mutations of p53, and eight cases (13.3%) showed p16/p14ARF deletion, including one case with both alterations. Among 32 cases with data on histologic chemoresponse, all 10 with alterations in p53 or p16/p14ARF showed a poor chemoresponse (P = .03). Variables predicting poorer overall survival included p53 mutation alone (P < .001), either p53 or p16/p14ARF alteration (P < .001), and stage (P < .01). In multivariate analysis, alterations of p53 and/or p16/p14ARF as a single variable, was the most adverse prognostic factor (P < .001), followed by stage (P = .04). In a multivariate analysis with alterations of p53 and p16/p14ARF as separate variables, both were significant (P < .001 and P = .03, respectively). Six cases with p16/p14ARF deletion were also studied for co-deletion of the contiguous methylthioadenosine phosphorylase gene, and this was detected in four cases.

Conclusion

Alterations in p53 or p16/p14ARF are found in a fourth of ES cases and define a subset with highly aggressive behavior and poor chemoresponse.

Responsiveness of CPT-11 in respect to hMLH1 and hMSH2 protein expression in the primary colorectal cancer

PURPOSE

The aim of this study was to evaluate the responsiveness to CPT-11 with respect to hMLH1 and hMSH2 protein expressions in primary colorectal tumors.

MATERIALS AND METHODS

91 patients with colorectal cancer treated having undergone surgery and postoperative CPT-11-based adjuvant chemotherapy, between 1997 and 2002, were prospectively recruited. Tumor samples were immunohistochemically analyzed for the expressions of hMLH1, hMSH2, p53 and CEA proteins.

RESULTS

Of the 91 tumors, 6 (6.6%) and 4 (4.4%) showed loss of hMLH1 and hMSH2 protein expressions, respectively. The response rate of patients with tumors not expressing either hMLH1 or hMSH2 was higher than that of those expressing either of these proteins (p=0.026). Patients with tumors not expressing hMLH1 showed a significantly better response to CPT-11 (p=0.04). The responsiveness was not associated with the expressions of hMSH2, p53 or CEA. There were no correlations between drug toxicity and the expressions of hMLH1, hMSH2 or p53. The overall survival was better in patients responsive to CPT-11-based chemotherapy compared to non-responders.

CONCLUSION

The immunohistochemical determination of loss of hMLH1 and hMSH2 expressions may be used in determining the responsiveness to CPT-11-based chemotherapy. Our results suggest that hMLH1 protein expression may be a predictor for CPT-11 responsiveness in patients with colorectal cancer.

Genetic Alterations in Locally Advanced Stage II/III Colon Cancer: A Search for Prognostic Markers

Heterogeneity in advanced colon cancer leads to different results from adjuvant chemotherapy. To identify groups of patients who may need adjuvant treatment, molecular staging and correlation with clinical data may be helpful in classifying histologically similar tumors. Colon cancer develops through a multistep process with an accumulation of multiple genetic alterations that are often the cause of a form of genomic instability. The 2 best known mechanisms of genomic instability are chromosomal instability (CIN) and microsatellite instability (MSI). The CIN phenotype is found in approximately 85% of sporadic colon cancers and is characterized by aneuploidy, multiple chromosomal rearrangements, and an accumulation of somatic mutations in oncogenes such as K-ras and tumor suppressor genes such as TP53 and APC. The MSI phenotype is associated with small insertions and deletions mainly in repetitive sequences (microsatellites) and is found in approximately 15% of cases. This instability, often referred to as high-frequency MSI (MSI-H), is caused by defects of the mismatch repair system, which is involved in repairing DNA errors that arise during DNA replication. Clear-cut correlations between the somatic genetic alterations in tumors and the clinical behavior of the tumor are rare. Only a few markers, such as MSI-H and TP53, seem to have a prognostic value. Mutations in the TP53 gene are associated with an aggressive tumor growth and subsequent reduced survival, whereas MSI-H seems to be correlated with a favorable outcome. In general, predicting biologic behavior of in particular stage III colon cancers is difficult and remains a great clinical problem.

Prognostic value of p27, p53, and vascular endothelial growth factor in Dukes A and B colon cancer patients undergoing potentially curative surgery

PURPOSE

Early-stage colon cancer patients (Dukes A or B; pT1-T3 pNO pMO) are excluded from adjuvant chemotherapy following potentially curative surgery because they are expected to have good long-term survival. However, 20 percent to 30 percent of these patients ultimately succumb from recurrent disease. This indicates that the conventional staging procedures may be unable to precisely predict cancer prognosis.

METHODS

In 65 early-stage colon cancers, we investigated by immunohistochemistry the role of molecular markers such as p27, p53, and vascular endothelial growth factor in identifying high-risk patients who may benefit from adjuvant treatments.

RESULTS

No clinicopathologic factor, namely Dukes stage, t parameter, number of resected nodes, and vascular or lymphatic invasion, was found be an independent significant predictor of disease-specific and disease-free survival. In contrast, each molecular marker predicted survival and recurrence rates much better than the conventional Dukes staging system. The best combination of variables for prediction of long-term outcome and recurrence rate included p27, p53, and vascular endothelial growth factor. Interestingly, the greater the number of molecular alterations, the lower the five-year estimated survival function. Nearly all cancer-related deaths were observed among patients whose colon cancers expressed all three molecular alterations. Regardless of Dukes stage, the recurrence rate was found to increase with the increase in the number of molecular alterations. Early-stage colon cancers expressing p27 down-regulation and high p53 and vascular endothelial growth factor immunoreactivity showed a 100 percent actuarial four-year recurrence rate.

CONCLUSIONS

Assessment of molecular alterations may be useful to identify a higher-risk group of early-stage colon cancer patients who may benefit from adjuvant chemotherapy.

Expression profiling of colorectal carcinomas using tissue microarrays: cell cycle regulatory proteins p21, p27, and p53 as immunohistochemical prognostic markers in univariate and multivariate analysis

With the rapidly growing understanding of tumor biology, molecular staging of cancer is expected to improve prognostication. This would be particularly important for cancers amenable to adjuvant treatment, such as colorectal carcinomas. To generate data for this, the tissue microarray technique may prove useful. Tissue microarrays were constructed with triplicate cores (0.6 mm diameter) from the invasive margins of a consecutive single-institution series of 184 colorectal carcinomas. Immunostaining for p53, p21, p27, Ecadherin, and beta-catenin was scored. Tumor cell proliferation was assessed by mitotic indices and Ki-67 labeling, apoptosis by quantification of apoptotic bodies. Reduced nuclear immunostaining for p21 (<10%) and p27 (< or =50%) and reduced membranous expression of Ecadherin were significantly associated with a poorer clinical course by univariate analysis. beta-catenin immunostaining had no prognostic impact. Mitotic and apoptotic indices as well as Ki-67 labeling below the median were indicators of poor prognosis. Complete absence of p53 nuclear staining was a significant adverse prognostic factor. By Cox regression, p53 = 0%, p53 = 0%, in combination with p27 < or = 50%, the mitotic index and the combined mitotic and apoptotic index added prognostic information to UICC stage. The authors found that growth pattern, lymphohistiocytic response, lymphatic permeation, and venous spread, too, each was a strong prognosticator in addition to UICC stage. The results support that tissue microarrays are a useful tool for screening immunohistochemical markers for prognostic use. An immunopanel of p21, p27, and p53 could be useful for prognostication in colorectal carcinoma in addition to UICC stage.

Technology platforms for pharmacogenomic diagnostic assays

Rapid advances in the understanding of genomic variation affecting drug responses, and the development of multiplex assay technologies, are converging to form the basis for new in vitro diagnostic assays. These molecular diagnostic assays are expected to guide the therapeutic treatment of many diseases, by informing physicians about molecular subtypes of disease that require differential treatment, which drug has the greatest probability of effectively managing the disease, and which individual patients are at the highest risk of experiencing adverse reactions to a given drug therapy. This article reviews some of the relative strengths and limitations of the most widely used technologies and platforms for such assays.

Systematic review of genetic influences on the prognosis of colorectal cancer

Background

In terms of genetics, colorectal cancer is one of the best understood of all malignant diseases. Genetic influences on prognosis may have far-reaching implications, especially for the design of surgical and chemoradiotherapeutic regimens. However, their significance in determining prognosis remains unclear. This study aimed to review the literature on the specific role of key genes in determining the survival of patients with colorectal cancer.

Methods

A Medline search was carried out to identify all original scientific papers relating colorectal cancer genetics to patient survival, up to December 2002. Cochrane and Embase databases were also searched. Identified articles were retrieved and searched carefully for additional information. This review includes K-ras, p53, DCC, NM23 and DNA mismatch repair genes.

Results and conclusion

Conflicting evidence exists as to the prognostic significance of genes commonly implicated in the pathogenesis of colorectal carcinoma. Possible causes for such discrepancy include differences in study methods and laboratory techniques, variable duration of follow-up, statistical differences in study power, and heterogeneity in study populations. Future studies should adopt standardized protocols to define clinically relevant genetic observations.

Paradoxes of Non-Trivial Gene Networks: How Cancer-Causing Mutations Can Appear to Be Cancer-Protective

Abnormalities of gene structure or expression are commonly found in cancers, where they are used as prognostic markers, predicting the likely severity of disease or chances of response to therapy. An odds ratio (OR) of <1 indicates that a marker's presence is correlated with better outcome. An OR of <1 is also often taken to mean that the gene concerned has a protective effect in the mechanism of cancer. I show that this is not necessarily so. Modeling of the genes involved in the causation of cancer as a network of weak, failure-prone elements shows that "cancer-causing" genes (i.e., genes whose abnormality is causal in driving cancer) can nevertheless appear as "protective" markers in later stage cancers. This implies that results suggesting that well-known oncogenes have an OR of <1 are quite valid, and that predicting a "protective" role from an apparently protective prognostic value is not valid. I identify mdm-2 and bax as candidates for genes with an apparently protective role through this mechanism.

p53 is an independent pre-treatment markers for long-term survival in stage II and III colorectal cancers: an analysis of interaction between genetic markers and fluorouracil-based adjuvant therapy

One hundred and thirty-eight stage II and III colorectal cancer patients were included to evaluate the prognostic significance of genetic markers (including mutations of the p53, K-ras genes, and microsatellite instability) on the response to 5-fluorouracil (FU)-based post-operative adjuvant therapies (PAT). When stratified by PAT and adjusting for other prognostic variables, presence of p53 mutation was associated with a poor outcome (hazard ratio (HR)=3.1, 95% confidence interval (CI), 0.9-11.0) among patients without PAT. Our data confirmed that p53 mutation is an independent pre-treatment factor in stage II and III colorectal cancer after curative resection.

Determination of molecular marker expression can predict clinical outcome in colon carcinomas

PURPOSE

Conventional staging procedures are often unable to precisely predict prognosis in colorectal cancer (CRC). In this study, we set out to investigate the possible role of molecular/structural indicators involved in cell cycle regulation (p27 and p53), apoptosis (p53 and p27), and tumor neoangiogenesis [p53, vascular endothelial growth factor (VEGF), and microvessel count] in predicting tumor behavior and clinical outcome in CRC patients

EXPERIMENTAL DESIGN

Analysis of the above indicators was performed by immunohistochemistry on 104 CRC patient samples and 25 normal colon mucosa specimens.

RESULTS

Intense p27 nuclear staining was found in normal colon mucosa, with p53 nuclear staining and VEGF cytoplasmic accumulation <10%, and low microvessel count. In contrast, in CRC samples, p27 was down-regulated in 53.8%, p53 protein was overexpressed in 52%, and VEGF stained positive in 67.3% of the cases, respectively. Multiple regression analysis showed that molecular markers were strongly correlated. In patients treated with curative surgery, a significant relationship was seen between p27 down-regulation and Dukes' stage, nodal status, and the presence of distant metastases. VEGF overexpression correlated significantly with Dukes' stage, tumor (t) and metastasis (m) parameters, and left site. Stepwise regression selected p27, p53, VEGF, and Dukes' stage as the best combination of variables capable of predicting both disease-specific and disease-free survival.

CONCLUSIONS

The investigated indicators may be useful for the prediction of outcome and recurrence rate in curatively treated CRC patients. In conjunction with clinical and pathological staging, they may provide a stronger indication of clinical outcome than staging alone and help better select therapeutic options in CRC patients.

Adverse prognostic effect of methylation in colorectal cancer is reversed by microsatellite instability

PURPOSE

DNA methylation is an important biologic event in colorectal cancer and in some cases is associated with the development of microsatellite instability (MSI). In this study, we sought to determine the prognostic significance of DNA methylation, both in univariate analysis and in concert with other clinicopathologic factors known to influence outcome.

PATIENTS AND METHODS

Fresh tissue (625 cancers) was obtained from 605 individuals (age range, 29 to 99 years) undergoing curative surgery for colorectal cancer at one institution during a period of 8 years. Clinicopathologic details were recorded for all tumors, including stage, grade, type, vascular space invasion, and clinical follow-up to 5 years. Microsatellite status was assessed using standard markers. Methylation of p16 and hMLH1 promoters was determined by methylation-specific polymerase chain reaction (PCR), whereas methylation at methylated-in-tumor loci (MINT)1, MINT2, MINT12, and MINT31 loci were assessed by bisulfite-PCR.

RESULTS

Patients with microsatellite unstable tumors (12%) had better disease-specific survival than those with microsatellite stable (MSS) tumors (univariate analysis: hazard ratio [HR], 0.53; 95% CI, 0.27 to 1.0). Overall survival of individuals with MSS tumors was influenced by three independently significant factors: tumor stage (HR, 7.3; 95% CI, 5.1 to 10.4), heavy tumor methylation (HR, 2.1; 95% CI, 1.1 to 4.0), and vascular space invasion (HR, 1.9; 95% CI, 1.3 to 2.9). In MSS tumors, methylation at any single site was not independently predictive of survival. Neither methylation nor microsatellite status predicted a favorable response to chemotherapy.

CONCLUSION

DNA methylation is associated with a worse outcome in colorectal cancer, but this adverse prognostic influence is lost in those methylated tumors showing MSI. The mechanisms of these events warrant additional investigation.

Prognostic molecular markers for planning adjuvant chemotherapy trials in Dukes' B colorectal cancer patients: how much evidence is enough?

The benefit of postoperative adjuvant chemotherapy in patients with Dukes' B colorectal cancer is still uncertain and its routine use is not recommended. Prognostic biomarkers may be useful for identifying high-risk patients with resected, node-negative disease, and this stratification may represent an innovative strategy for designing adjuvant chemotherapy trials. Featured prognostic molecular markers can be divided into the following categories: cell proliferation indices (Ki-67, Mib-1, proliferating cell nuclear antigen); oncogenes/tumor suppressor genes [p53, K-ras, Deleted in Colorectal Cancer (DCC), Bcl-2, c-erbB2]; DNA repair (microsatellite instability); markers of angiogenesis (vascular count, vascular endothelial growth factor); markers of invasion/metastasis (plasminogen-related molecules, matrix metalloproteinases); and biochemical markers (thymidylate synthase). Studies that have investigated their prognostic role in Dukes' B colorectal cancer patients are reviewed here. Current data do not provide sufficient evidence for the incorporation of available prognostic biomarkers into clinical practice. However, a biomarker-based approach could be an effective strategy for improving results of postoperative adjuvant treatments in high-risk Dukes' B colorectal cancer patients. Markers of altered DCC function have shown promising prognostic role and sufficient prevalence in retrospective investigations and they deserve further assessment in prospective studies.

Genetic tumor markers with prognostic impact in Dukes' stages B and C colorectal cancer patients

PURPOSE

To examine several genetic changes in primary colorectal carcinomas (CRCs) from patients with 10 years of follow-up and associate the findings with clinicopathologic variables.

MATERIAL AND METHODS

DNA from 220 CRCs were analyzed for allelic imbalances at 12 loci on chromosome arms 1p, 14q, 17p, 18q, and 20q, and the microsatellite instability (MSI) status was determined. The clinical significance of the tumor protein 53 (TP53) mutations was re-evaluated.

RESULTS

Patients with tumors containing 17p or 18q deletions had shorter survival than those without these alterations (P =.021, P =.008, respectively). This was also significant for the Dukes' B group (P =.025, P =.010, respectively). Furthermore, patients with tumors showing losses of both chromosome arms revealed an even poorer disease outcome than those with either 17p or 18q loss. Patients with low increase in 20q copy number in their tumors had longer survival compared with those without changes (P =.009) or those with a high increase of copy number (P =.037). This was also evident for the Dukes' C group (P =.018, P =.030, respectively). MSI was seemingly a beneficial marker for survival (P =.071). A significant association between mutations affecting the L3 zinc-binding domain of TP53 and survival was confirmed in this cohort after 10 years of follow-up, and also was found to apply for patients in the Dukes' B group. Several associations were found among genetic and pathologic data.

CONCLUSION

The present study indicates that 17p, 18q, and 20q genotypes, and TP53 mutation status add information in the subclassification of Dukes' B and C patients and may have impact on the choice of treatment.

P53 overexpression predicts poor chemosensitivity to high-dose 5-fluorouracil plus leucovorin chemotherapy for stage IV colorectal cancers after palliative bowel resection

Our study aims to further clarify the prognostic significance of p53 overexpression in stage IV colorectal cancer. Between January 1994 and June 1997, we recruited 144 patients with stage IV colorectal cancers for our study, based on appropriate eligibility criteria. The patients were nonrandomly allocated to 2 treatment groups of either with or without high-dose 5-fluorouracil plus leucovorin chemotherapy (HDFL: 5-Fu: 2,600 mg/m(2) leucovorin 300 mg/m maximum 500 mg). Each treatment group was further divided into 2 subgroups according to the status of p53 overexpression. Therefore, 4 subgroups were allocated in our study and were designated as p53 (overexpression) HDFL (+), n = 65; p53 (normal) HDFL (+), n = 37; p53 (overexpression) HDFL (-), n = 27; and p53 (normal) HDFL (-), n = 15, respectively. All patients were prospectively followed until April 2001. There was no significant difference of the background clinicopathologic data of these 4 allocated subgroups of patients (p > 0.05). Multivariate analysis of various clinicopathologic factors of the whole group of patients indicated that age > or = 60 years, poor differentiation, mucin production, CEA > 100 ng/ml, p53 overexpression and without chemotherapy were the significant independent poor prognostic factors (p < 0.05). Survival analyses indicated that the patients of subgroup p53 (normal) HDFL (+) survived significantly longer than those of subgroup p53 (overexpression) HDFL (+), with mean survival time (95% confidence interval [CI]) of 20.24 (16.24-24.25) and 13.29 (10.98-15.60) months, respectively (p = 0.0043, log-rank test). In contrast, in patients without chemotherapy, the prognosis was poor regardless of their p53 status, with mean survival time (95% CI) of 6.85 (5.47-8.23) and 5.87 (4.48-7.26) months in p53 (overexpression) HDFL (-) and p53 (normal) HDFL (-) subgroups of patients, respectively (p = 0.2820, log-rank test). Cancers of normal p53 expression responded significantly better to HDFL (p < 0.05), with mean response rate (95% CI) being 65.57% (52.18-82.96%) in subgroup p53 (normal) HDFL (+) as compared to 35.38% (23.52-47.24%) in subgroup p53 (overexpression) HDFL (+). The toxicity to HDFL was similarly minimal between p53-normal and p53-overexpression patients (p > 0.05). We thus concluded that the poorer prognosis of stage IV colorectal cancers with p53 overexpression was associated with their poorer chemosensitivity rather than the more biologic aggressiveness.

Splicing mutations in TP53 in human squamous cell carcinoma lines influence immunohistochemical detection

The mutational status of the tumor suppressor gene TP53 is often examined by immunohistochemistry. We compared the incidence of TP53 mutations in 12 permanent squamous cell carcinoma lines of the head and neck with the immunohistochemical staining obtained with two different antibodies. The mutational status of the TP53 gene was assessed by sequencing the complete coding frame of the TP53 mRNA. All 12 tumor cell lines had TP53 mutations. Six of them showed missense mutations and five had premature stop codons caused either by splicing mutations or nonsense mutations or by exon skipping. One tumor cell line was heterozygous, with a truncating splicing mutation and an additional missense mutation located on different alleles. In one case, an in-frame insertion of 23 extra codons was found. All missense mutations were positive in immunhistochemistry and Western blotting. The truncated p53 was not immunohistochemically detected in three cases with the DO-7 antibody and in five cases with the G59-12 antibody, giving false-negative results in 25% or 40%, respectively, of all tumor cell lines examined. We conclude that splicing mutations are common in squamous cell carcinoma lines and that the incidence of p53 inactiviation by erroneous splicing is higher than yet reported. Sequencing of only the exons of TP53 may miss intronic mutations leading to missplicing and may therefore systematically underestimate the TP53 mutation frequency.

TP53: a key gene in human cancer

TP53 is mutated in most types of human cancers and is one of the most popular genes in cancer research. The p53 protein is a sensor of multiple forms of genotoxic, oncogenic and non-genotoxic stress. It suppresses growth and controls survival of stressed cells, and as such, is the focal point of selection pressures in tissues exposed to carcinogens or to oncogenic changes. Thus, the clonal expansion of cells with mutations in TP53 may be seen as the result of a selection process intrinsic to the natural history of cancer. In this review, we discuss the nature of these various forms of selection pressure. We present a hypothesis to explain why TP53 is often mutated as either an early or a late event in cancer. Furthermore, we also summarise current knowledge on the molecular consequences of mutation for loss of wild-type protein function, dominant-negative activity, and a possible gain of oncogenic function.