Enriched SSCP: a highly sensitive method for the detection of unknown mutations. Application to the molecular diagnosis of lung cancer in sputum samples

Circulating tumor DNA minimal residual disease in clinical practice of non-small cell lung cancer

INTRODUCTION

The advance of diagnostics and treatments has greatly improved the prognosis of non-small cell lung cancer (NSCLC) patients. However, relapse and metastasis are still common problems encountered by NSCLC patients who have achieved complete remission. Therefore, overcoming the challenge of relapse and metastasis is particularly important for improving the prognosis of NSCLC patients. Research has shown that minimal residual disease (MRD) was a potential source of tumor relapse and metastasis, and circulating tumor DNA (ctDNA) MRD has obvious advantages in predicting the relapse and metastasis of NSCLC and evaluating treatment effectiveness. Therefore, dynamic monitoring of MRD is of great significance for NSCLC patient management strategies.

AREAS COVERED

We have reviewed articles related to NSCLC MRD included in PubMed and describes the biological significance and historical context of MRD research, reasons for using ctDNA to evaluate MRD, and potential value and challenges of ctDNA MRD in assessing relapse and metastasis of NSCLC, ultimately guiding clinical therapeutic strategies and management.

EXPERT OPINION

The standardized scope of ctDNA MRD detection for NSCLC requires more clinical research evidence to minimize study differences, making it possible to include in the clinical staging as a reliable indicator.

Preproenkephalin hypermethylation in the pure pancreatic juice compared with p53 mutation in the diagnosis of pancreatic carcinoma

BACKGROUND

Aberrant methylation of CpG islands is a common mechanism for the dysregulation of tumor suppressor genes in a variety of human malignancies. Preproenkephalin ppENK) hypermethylation is recognized in 90% of pancreatic carcinoma (PCa) tissues, but not in normal pancreas. We analyzed ppENK hypermethylation in pure pancreatic juice (PPJ) in patients with PCa, intraductal papillary mucinous neoplasms (IPMN), and chronic pancreatitis (CP), and elucidated its usefulness as a marker in the diagnosis of PCa compared with p53 mutation.

METHODS

PPJ was collected endoscopically from 28 patients with PCa, 15 patients with IPMN, and 20 patients with CP. DNA was extracted from the supernatant and the sediment of PPJ. Methylation-specific polymerase chain reaction was performed for hypermethylation analysis of ppENK. In addition, single-strand conformation polymorphism and direct sequencing were performed simultaneously to identify p53 mutations.

RESULTS

The incidence of ppENK hypermethylation in the supernatant and/or the sediment of PPJ was 50% (14 of 28) in patients with PCa. In contrast, the incidence of ppENK hypermethylation was 26.7% (4 of 15) in patients with IPMN, and 5% (1 of 20) in patients with CP (P < 0.002). The incidence of p53 mutations in the PPJ was 42.9% (12 of 28) in patients with PCa and 0% (0 of 20) in patients with CP. Furthermore, the incidence of ppENK hypermethylation and/or p53 mutations in the PPJ was enhanced to 67.9% (19 of 28) in patients with PCa in the combination assay.

CONCLUSIONS

These results suggest that ppENK hypermethylation in PPJ is specific for cancer, and the combination assay with p53 enhances the genetic diagnosis of PCa.

Gene mutation as a target for early detection in cancer diagnosis

The increasing number of genetic aberrations implicated in the development of human cancer has prompted a search to detect them at the earliest possible stage of their formation. Of the many such genetic changes identified thus far, relatively few meet the standard for markers in early diagnosis and prognosis, namely that the genetic modifications occur during the early onset phase of cancer development. Parallel to the increasing number of such genes is the growing availability of technologies using more powerful and cost-efficient methods that enable mass screening for genetic alterations. The purpose of this review is to summarize the currently available genes that can serve as markers for early detection of cancers and methods that allow their detection.

Genetic heterogeneity in saliva from patients with oral squamous carcinomas: implications in molecular diagnosis and screening

We performed microsatellite analysis at chromosomal regions frequently altered in head and neck squamous carcinoma on matched saliva and tumor samples from 37 patients who had oral squamous carcinoma. The results were correlated with the cytologic findings and traditional clinicopathologic factors to assess the diagnostic and biological potential of these markers. Our data showed that 18 (49%) of the saliva samples and 32 (86%) of the tumors had loss of heterozygosity (LOH) in at least one of the 25 markers studied. In saliva, the combination of markers D3S1234, D9S156, and D17S799 identified 13 (72.2%) of the 18 patients with LOH in saliva (P < 0.001). For tumors, markers D3S1234, D8S254, and D9S171 together identified 27 (84.3%) of the 32 tumors with LOH at any of the loci tested (P < 0.001). Eleven (55%) of the 20 saliva samples with cytologic atypia and seven (35%) of the 17 specimens without atypia had LOH. Significant correlation between LOH in tumor at certain markers and smoking and alcohol use was found. Our results indicate that: 1) epithelial cells in saliva from patients with head and neck squamous tumorigenesis provide suitable material for genetic analysis; 2) combined application of certain markers improves the detection of genetic alteration in these patients; 3) clonal heterogeneity between saliva and matching tumor supports genetic instability of the mucosal field in some of these patients; and 4) LOH at certain chromosomal loci appears to be associated with smoking and alcohol consumption.

Discordance between K-ras mutations in bone marrow micrometastases and the primary tumor in colorectal cancer

PURPOSE

To study bone marrow micrometastases from colorectal cancer patients for the presence of K-ras mutations and to compare their genotype with that of the corresponding primary tumor.

PATIENTS AND METHODS

Bilateral iliac crest aspiration was performed in 51 patients undergoing surgery for colorectal cancer, and bone marrow micrometastases were detected by immunohistochemistry. The presence of K-ras mutations was determined by single-strand conformation polymorphism analysis on both primary tumors and paired bone marrow samples and was confirmed by sequencing.

RESULTS

In six patients with primary tumor mutations, it was possible to amplify a mutated K-ras gene also from the bone marrow sample. In three of those patients the pattern of K-ras mutations differed between both samples, in two patients the mutation was identical between the bone marrow and its primary tumor, and in one patient the same mutation plus a different one were found. Fifteen of 17 K-ras mutations found in primary tumors were located in codon 12, whereas in bone marrow, five of seven mutations were found in codon 13 (P =.003).

CONCLUSION

Our results demonstrate that, at least for K-ras mutations, disseminated epithelial cells are not always clonal with the primary tumor and they question the malignant genotype of bone marrow micrometastases. They also indicate that different tumoral clones may be circulating simultaneously or sequentially in the same patient. Analysis of the type of mutations suggests that cell dissemination might be an early event in colorectal carcinogenesis.

Molecular characterization of minimal residual cancer cells in patients with solid tumors

The failure to reduce the mortality of patients with solid tumors is mainly a result of the early dissemination of cancer cells to secondary sites, which is usually missed by conventional diagnostic procedures used for tumor staging. PCR was shown to be superior to conventional techniques in detecting circulating tumor cells and micrometastases allowing the identification of one tumor cell in up to 10(7) normal cells in various sources such as blood, bone marrow, lymph nodes, urine or stool. The methods used are based on the detection of either genomic alterations in oncogenes and tumor suppressor genes or on the mRNA expression of tissue-specific and tumor-associated genes. The additional implementation of techniques for cancer cell purification had a significant impact on analytical sensitivity and specificity of MRCC detection. For patients with e.g. melanoma, breast, colorectal or prostate cancer it was demonstrated that the presence of disseminated cancer cells defines a subgroup of patients with reduced time to recurrence. The possibility to use easily accessible body fluids as a source for MRCC detection enables longitudinal observations of the disease. In this review we discuss the potential of molecular characterization of MRCC as a tool to improve prognostication, therapy selection and drug targeting as well as therapy monitoring.

Multi-step evolution of lung cancer

In an attempt to improve the poor survival rates for lung cancer, therapeutic strategies require a deeper understanding of the biological events contributing to the formation and progression of the disease. In particular, the importance of studying the different stages of lung cancer including early pre-neoplasia is being recognised and studies examining genetic changes in pre-invasive and invasive lesions are being used to identify key events in tumorigenesis.