Formalin fixing with paraffin embedding (FFPE) has been a standard sample preparation method for decades, and archival FFPE samples are still very useful resources. Nonetheless, the use of FFPE samples in cancer genome analysis using next-generation sequencing, which is a powerful technique for the identification of genomic alterations at the nucleotide level, has been challenging due to poor DNA quality and artificial sequence alterations. In this study, we performed whole-exome sequencing of matched frozen samples and FFPE samples of tissues from 4 cancer patients and compared the next-generation sequencing data obtained from these samples. The major differences between data obtained from the 2 types of sample were the shorter insert size and artificial base alterations in the FFPE samples. A high proportion of short inserts in the FFPE samples resulted in overlapping paired reads, which could lead to overestimation of certain variants; >20% of the inserts in the FFPE samples were double sequenced. A large number of soft clipped reads was found in the sequencing data of the FFPE samples, and about 30% of total bases were soft clipped. The artificial base alterations, C>T and G>A, were observed in FFPE samples only, and the alteration rate ranged from 200 to 1,200 per 1M bases when sequencing errors were removed. Although high-confidence mutation calls in the FFPE samples were compatible to that in the frozen samples, caution should be exercised in terms of the artifacts, especially for low-confidence calls. Despite the clearly observed artifacts, archival FFPE samples can be a good resource for discovery or validation of biomarkers in cancer research based on whole-exome sequencing.

The novel fusion gene and its protein TRP-ALK, harboring coiled-coil and kinase domains, could possess transforming potential and responses to treatment with ALK inhibitors. This case is the first report of TPR-ALK fusion transcript in clinical tumor samples and could provide a novel diagnostic and therapeutic candidate target for patients with cancer, including non-small-cell lung carcinoma.

The novel fusion gene and its protein HIP1-ALK harboring epsin N-terminal homology, coiled-coil, juxtamembrane, and kinase domains, which could play a role in carcinogenesis, could become diagnostic and therapeutic target of the lung adenocarcinoma and deserve a further study in the future.

Recently, conjoined genes (CGs) have emerged as important genetic factors necessary for understanding the human genome. However, their formation mechanism and precise structures have remained mysterious. Based on a detailed structural analysis of 57 human CG transcript variants (CGTVs, discovered in this study) and all (833) known CGs in the human genome, we discovered that the poly(A) signal site from the upstream parent gene region is completely removed via the skipping or truncation of the final exon; consequently, CG transcription is terminated at the poly(A) signal site of the downstream parent gene. This result led us to propose a novel mechanism of CG formation: the complete removal of the poly(A) signal site from the upstream parent gene is a prerequisite for the CG transcriptional machinery to continue transcribing uninterrupted into the intergenic region and downstream parent gene. The removal of the poly(A) signal sequence from the upstream gene region appears to be caused by a deletion or truncation mutation in the human genome rather than post-transcriptional trans-splicing events. With respect to the characteristics of CG sequence structures, we found that intergenic regions are hot spots for novel exon creation during CGTV formation and that exons farther from the intergenic regions are more highly conserved in the CGTVs. Interestingly, many novel exons newly created within the intergenic and intragenic regions originated from transposable element sequences. Additionally, the CGTVs showed tumor tissue-biased expression. In conclusion, our study provides novel insights into the CG formation mechanism and expands the present concepts of the genetic structural landscape, gene regulation, and gene formation mechanisms in the human genome.

PurposeHereditary cancer syndrome means that inherited genetic mutations can increase a person's risk of developing cancer. We assessed the frequency of germline mutations using an nextgeneration sequencing (NGS)–based multiple-gene panel containing 64 cancer-predisposing genes in Korean breast cancer patients with clinical features of hereditary breast and ovarian cancer syndrome (HBOC).Materials and MethodsA total of 64 genes associated with hereditary cancer syndrome were selected for development of an NGS-based multi-gene panel. Targeted sequencing using the multi-gene panel was performed to identify germline mutations in 496 breast cancer patients with clinical features of HBOC who underwent breast cancer surgery between January 2002 and December 2017.ResultsOf 496 patients, 95 patients (19.2%) were found to have 48 deleterious germline mutations in 16 cancer susceptibility genes. The deleterious mutations were found in 39 of 250 patients (15.6%) who had breast cancer and another primary cancer, 38 of 169 patients (22.5%) who had a family history of breast cancer (≥ 2 relatives), 16 of 57 patients (28.1%) who had bilateral breast cancer, and 29 of 84 patients (34.5%) who were diagnosed with breast cancer at younger than 40 years of age. Of the 95 patients with deleterious mutations, 60 patients (63.2%) had <i>BRCA1/2</i> mutations and 38 patients (40.0%) had non-<i>BRCA1/2</i> mutations. We detected two novel deleterious mutations in <i>BRCA2</i> and <i>MLH1</i>.ConclusionNGS-based multiple-gene panel testing improved the detection rates of deleterious mutations and provided a cost-effective cancer risk assessment.

SMAD4 has been suggested to inhibit the activity of the WNT/b-catenin signaling pathway in cancer. However, the mechanism by which SMAD4 antagonizes WNT/b-catenin signaling in cancer remains largely unknown. Aurora A kinase (AURKA), which is frequently overexpressed in cancer, increases the transcriptional activity of b-catenin/T-cell factor (TCF) complex by stabilizing b-catenin through the inhibition of GSK-3b. Here, SMAD4 modulated AURKA in a TGFb-independent manner. Overexpression of SMAD4 significantly suppressed AURKA function, including colony formation, migration, and invasion of cell lines. In addition, SMAD4 bound to AURKA induced degradation of AURKA by the proteasome. A luciferase activity assay revealed that the transcriptional activity of the b-catenin/TCF complex was elevated by AURKA, but decreased by SMAD4 overexpression. Moreover, target gene analysis showed that SMAD4 abrogated the AURKA-mediated increase of b-catenin target genes. However, this inhibitory effect of SMAD4 was abolished by overexpression of AURKA or silencing of AURKA in SMAD4-overexpressed cells. Meanwhile, the SMAD4-mediated repression of AURKA and b-catenin was independent of TGFb signaling because blockage of TGFbR1 or restoration of TGFb signaling did not prevent suppression of AURKA and b-catenin signaling by SMAD4. These results indicate that the tumor-suppressive function of SMAD4 is mediated by downregulation of b-catenin transcriptional activity via AURKA degradation in a TGFb-independent manner.

REarranged during Transfection (RET) fusion genes are detected in approximately 1% of lung adenocarcinomas and known primarily as oncogenic driver factors. Here, we found a novel RET fusion gene, KIAA1217-RET, and examined the functional differences of RET51 and RET9 protein, fused with KIAA1217 in cancer progression and drug response. KIAA1217-RET, resulting from the rearrangement of chromosome 10, was generated by the fusion of KIAA1217 exon 11 and RET exon 11 from a non-small cell lung cancer patient. Expression of this gene led to increased cell growth and invasive properties through activations of the PI3K/AKT and ERK signaling pathways and subsequently enabled oncogenic transformation of lung cells. We observed that cells expressing KIAA1217-RET9 fusion protein were more sensitive to vandetanib than those expressing KIAA1217-RET51 and both isoforms attenuated cellular growth via cell cycle arrest. These results demonstrated that KIAA1217-RET fusion represents a novel oncogenic driver gene, the products of which are sensitive to vandetanib treatment, and suggested that the KIAA1217-RET-fusion gene is a promising target for lung cancer treatment.

Transducer of ERBB2.1 (TOB1) is a tumor-suppressor protein, which functions as a negative regulator of the receptor tyrosine-kinase ERBB2. As most of the other tumor suppressor proteins, TOB1 is inactivated in many human cancers. Homozygous deletion of TOB1 in mice is reported to be responsible for cancer development in the lung, liver, and lymph node, whereas the ectopic overexpression of TOB1 shows anti-proliferation, and a decrease in the migration and invasion abilities on cancer cells. Biochemical studies revealed that the anti-proliferative activity of TOB1 involves mRNA deadenylation and is associated with the reduction of both cyclin D1 and cyclin-dependent kinase (CDK) expressions and the induction of CDK inhibitors. Moreover, TOB1 interacts with an oncogenic signaling mediator, β-catenin, and inhibits β-catenin-regulated gene transcription. TOB1 antagonizes the v-akt murine thymoma viral oncogene (AKT) signaling and induces cancer cell apoptosis by activating BCL2-associated X (BAX) protein and inhibiting the BCL-2 and BCL-XL expressions. The tumor-specific overexpression of TOB1 results in the activation of other tumor suppressor proteins, such as mothers against decapentaplegic homolog 4 (SMAD4) and phosphatase and tensin homolog-10 (PTEN), and blocks tumor progression. TOB1-overexpressing cancer cells have limited potential of growing as xenograft tumors in nude mice upon subcutaneous implantation. This review addresses the molecular basis of TOB1 tumor suppressor function with special emphasis on its regulation of intracellular signaling pathways.