Youn Jin Choi

Clinical significance of human papillomavirus genotyping

Cervical cancer is the fourth most common cancer in women worldwide, and the human papillomavirus (HPV) is the main causative agent for its development. HPV is a heterogeneous virus, and a persistent infection with a high-risk HPV contributes to the development of cancer. In recent decades, great advances have been made in understanding the molecular biology of HPV, and HPV’s significance in cervical cancer prevention and management has received increased attention. In this review, we discuss the role of HPV genotyping in cervical cancer by addressing: clinically important issues in HPV virology; the current application of HPV genotyping in clinical medicine; and potential future uses for HPV genotyping.

Frameshift mutation of a histone methylation-related gene SETD1B and its regional heterogeneity in gastric and colorectal cancers with high microsatellite instability.

Histone methyltransferase (HMT), which catalyzes a histone methylation, is frequently altered in cancers at mutation and expression levels. The aims of this study were to explore whether SETD1B, SETDB2, and SETD2, SET domain-containing HMT genes, are mutated and expressionally altered in gastric (GC) and colorectal cancers (CRC). In a public database, we found that SETD1B, SETDB2, and SETD2 had mononucleotide repeats in coding sequences that might be mutation targets in cancers with microsatellite instability (MSI). We analyzed the mutations in 76 GCs and 93 CRCs and found SETD1B (38.7% of GC and 35.6% of CRC with high MSI [MSI-H]), SETDB2 (11.1% of CRC with MSI-H), and SETD2 frameshift mutations (6.7% of CRC with MSI-H). These mutations were not found in stable MSI/low MSI. In addition, we analyzed intratumoral heterogeneity (ITH) of SETD1B mutation in 6 CRCs and found that 2 CRCs harbored regional ITH of SETD1B. We also analyzed SETD1B expression in GC and CRC by immunohistochemistry. Loss of SETD1B expression was identified in 15% to 55% of the GC and CRC with respect to the MSI status. Of note, the loss of expression was more common in those with SETD1B mutations than those with wild-type SETD1B. We identified alterations of SET domain-containing HMT at various levels (frameshift mutations, genetic ITH, and expression loss), which together might play a role in tumorigenesis of GC and CRC with MSI-H. Our data suggest that mutation analysis in multiple regions is needed for a better evaluation of mutation status in CRC with MSI-H.

Frameshift mutations of axon guidance genes ROBO1 and ROBO2 in gastric and colorectal cancers with microsatellite instability

Aims: Several lines of evidence indicate that axon guidance genes are involved not only in neural development but also in cancer development. ROBO1 and ROBO2, crucial regulators of axon guidance, are considered potential tumour suppressor genes. The aim of this study was to explore whether ROBO1 and ROBO2 genes are somatically mutated and expressionally altered in gastric (GC) and colorectal cancers (CRC). Methods: In a public database, we observed that both ROBO1 and ROBO2 had mononucleotide repeats in their coding exons that could be mutation targets in cancers with microsatellite instability (MSI). We analysed mutations of these repeats in 77 GC and 88 CRC either with high MSI (MSI-H) or low MSI/microsatellite stability (MSI-L/MSS) by single-strand conformation polymorphism (SSCP) and DNA sequencing. We analysed ROBO1 and ROBO2 expressions in GC and CRC by immunohistochemistry as well. Results: Overall, we found five ROBO1 and five ROBO2 frameshift mutations in the repeats. They were detected exclusively in the cancers with MSI-H (10/70, 14.2%), but not in MSI-L/MSS (0/95, 0%) (p = 0.018). In the immunohistochemistry, loss of ROBO2 expression was identified in 22 (29%) and 17 (19%) of GC and CRC, respectively, while increased expression of ROBO2 was found in 15 (20%) and 22 (25%) of GC and CRC, respectively. There were co-occurrences of mutation and loss of expression in both ROBO1 (4/5, 80% mutated cases, p < 0.001) and ROBO2 (5/5, 100% mutated cases, p < 0.05) genes. Conclusion: This is the first report of ROBO1 and ROBO2 frameshift mutations in GC and CRC. Frameshift mutations of ROBO1 and ROBO2 genes and alteration of ROBO2 expression in GC and CRC suggest that both genes might play roles in the pathogenesis of GC and CRC.

Intraindividual genomic heterogeneity of high-grade serous carcinoma of the ovary and clinical utility of ascitic cancer cells for mutation profiling

Intraindividual tumoural heterogeneity (ITH) is a hallmark of solid tumours and impedes accurate genomic diagnosis and selection of proper therapy. The aim of this study was to identify ITH of ovarian high‐grade serous carcinomas (OSCs) and to determine the utility of ascitic cancer cells as a resource for mutation profiling in spite of ITH. We performed whole‐exome sequencing, copy number profiling and DNA methylation profiling of four OSC genomes by using multiregional biopsies from 13 intraovarian lesions, 12 extraovarian tumour lesions (omentum/peritoneum), and ascitic cells. We observed substantial levels of heterogeneity in mutations and copy number alterations (CNAs) of the OSCs. We categorized the mutations into ‘common’, ‘shared’ and ‘private’ according to the regional distribution. Six common, eight shared and 24 private mutations were observed in known cancer‐related genes. Common mutations had a higher mutant allele frequency, and included TP53 mutations in all four OSCs. Region‐specific chromosomal amplifications and deletions involving BRCA1, PIK3CA and RB1 were also identified. It is of note that the mutations detected in ascitic cancer cells represented 92.3–100% of overall somatic mutations in the given case. Phylogenetic analyses of ascitic genomes predicted a polyseeding origin of somatic mutations in ascitic cells. Our results demonstrate that, despite ITH, somatic mutations, CNAs and DNA methylations in both ‘common’ category and cancer‐related genes were highly conserved in ascitic cells of OSCs, highlighting the clinical relevance of genome analysis of ascitic cells. Ascitic tumour cells may serve as a potential resource for discovering somatic mutations of primary OSC with diagnostic and therapeutic relevance. Copyright

Genomic landscape of endometrial stromal sarcoma of uterus

Although recurrent gene fusions such as JAZF1-JJAZ1 are considered driver events for endometrial stromal sarcoma (ESS) development, other genomic alterations remain largely unknown. In this study, we performed whole-exome sequencing, transcriptome sequencing and copy number profiling for five ESSs (three low-grade ESS (LG-ESS) and two undifferentiated uterine sarcomas (UUSs)). All three LG-ESSs exhibited either one of JAZF1-SUZ12, JAZF1-PHF1 and MEAF6-PHF1 fusions, whereas the two UUSs did not. All ESSs except one LG-ESS exhibited copy number alterations (CNAs), many of which encompassed cancer-related genes. In UUSs, five CNAs encompassing cancer-related genes (EZR, CDH1, RB1, TP53 and PRKAR1A) accompanied their expressional changes, suggesting that they might stimulate UUS development. We found 81 non-silent mutations (35 from LG-ESSs and 46 from UUSs) that included 15 putative cancer genes catalogued in cancer-related databases, including PPARG and IRF4 mutations. However, they were non-recurrent and did not include any well-known mutations, indicating that point mutations may not be a major driver for ESS development. Our data show that gene fusions and CNAs are the principal drivers for LG-ESS and USS, respectively, but both may require additional genomic alterations including point mutations. These differences may explain the different biologic behaviors between LG-ESS and UUS. Our findings suggest that ESS development requires point mutations and CNAs as well as the gene fusions.

Pure nongestational choriocarcinoma of the ovary: a case report

Pure ovarian choriocarcinoma can be gestational or nongestational in origin. Nongestational choriocarcinoma of the ovary is extremely rare, and its diagnosis is very difficult during the reproductive years. We present a case of a 33-year-old woman diagnosed with pure nongestational ovarian choriocarcinoma. Following surgery, multiple courses of a chemotherapy regimen of etoposide, methotrexate, and actinomycin-D (EMA) were effective.

Expression of DNA cytosine deaminase APOBEC3 proteins, a potential source for producing mutations, in gastric, colorectal and prostate cancers.

Aims and Background APOBEC3B is a deaminase that possesses DNA C-to-T editing activity. A recent report showed that APOBEC3B mRNA was overexpressed in breast cancer and that its expression was responsible for the high C-to-T mutation spectrum in breast cancer, suggesting that APOBEC3B could serve as a source for producing mutations. To see whether APOBEC3B is overexpressed in other common cancers at the protein level, we investigated APOBEC3 protein expression in 100 gastric, 103 colorectal and 107 prostate cancer tissues as well as in 10 breast cancers by immunohistochemistry using antibody that could detect APOBEC3B, APOBEC3F and APOBEC3D proteins. Results In the cancers, APOBEC3 expression was detected in 100% of breast cancers, 67% of gastric, 84% of colorectal and 67% of prostate cancer. Also, it was expressed in 100% of normal breast, 90% of normal stomach, 82% of normal colon and 93% of normal prostate tissues. In contrast to earlier data that showed an increased APOBEC3B expression in breast cancer cells compared to normal breast cells, APOBEC3 expression in cancers was lower than in normal tissues (gastric and prostate cancer) or was not different from normal tissues (colorectal and breast cancer). There was no significant association of APOBEC3 expression with clinocopathological parameters, including histology, metastasis and stage. Conclusions Our data indicate that APOBEC3 overexpression might not be restricted to specific cancer types. Also, APOBEC3 expression in many normal epithelial cells suggests that there might be a mutation unrelated function of APOBEC3 in the normal cells.

Mutational and expressional analysis of ERBB3 gene in common solid cancers

ERBB3 is a member of EGFR family receptor tyrosine kinases, genetic alterations of which are common and therapeutically targeted in human cancers. Recently, somatic mutations of ERBB3 gene, including recurrent mutation in exon 3 altering Val104, were reported in gastric cancers (GC) and colorectal cancers (CRC), strongly suggesting its role in the development of GC and CRC. To examine whether the recurrent ERBB3 mutations of exon 3 occur in GC and CRC, and other malignancies as well, we analyzed the ERBB3 in 1677 cancer tissues by a single‐strand conformation polymorphism (SSCP) assay. We identified ERBB3 mutations altering the Val104 mutations in GC (0.5%) and CRC (2.2%). However, we did not find the ERBB3 mutations in the other cancers besides GC and CRC. We observed that an increased intensity of phosphorylated ERBB3 (pERBB3) in GC and CRC. Of note, all of the cancers with ERBB3 mutations displayed an increased intensity of pERBB3 immunostaining. Our data indicate that the recurrent ERBB3 mutations altering Val104 occur predominantly in GC and CRC. Also, the data suggest that ERBB3 is altered in GC and CRC by various ways, including somatic mutations and increased expression that might play roles in tumorigenesis.

Laparoscopic upper vaginectomy for post-hysterectomy high risk vaginal intraepithelial neoplasia and superficially invasive vaginal carcinoma

BackgroundThe aim of this study is to describe the feasibility and efficacy of the laparoscopic upper vaginectomy (LUV) in vaginal intraepithelial neoplasia(VAIN) and superficially invasive vaginal carcinoma.MethodsWe studied patients with vaginal intraepithelial neoplasia (VAIN) 2, VAIN 3, and superficially invasive vaginal carcinoma after hysterectomy who have been under laparoscopic upper vaginectomy between March 2010 and March 2012.ResultsFour patients underwent LUV after hysterectomy for high risk VAIN and early vaginal cancer. The mean age was 50.8 (range 40–56) years; the mean operation time was 162.5 (range 145–205) minutes; and the mean estimated blood loss was 55 (range 20–100) ml. All the patients restituted bladder function after the removal of the foley catheter. Mean hospital stay was 2 days. Two patients had postoperative complications. One patient with warfarin administration had vaginal stump bleeding and another developed vesico-vaginal fistula. Three of the patients had no residual lesion, but 1 patient had VAIN 1 in the resection margin. Colposcopy was followed on all patients and cytology proved no recurrence.ConclusionsLUV after hysterectomy is a feasible procedure and attentively applicable to high risk VAIN or superficially invasive vaginal carcinoma.

Whole-exome sequencing identified the genetic origin of a mucinous neoplasm in a mature cystic teratoma

Mucinous tumour arising from a mature cystic teratoma associated with pseudomyxoma peritonei (PMP) is a rare disease and its tissue origin is not easy to specify by conventional histological and immunohistochemical analyses. To identify the origin of a secondary tumour arising from a mature teratoma, we performed whole-exome sequencing of a PMP secondary to a primary ovarian mucinous tumour. The mucinous tumour was CK20 (+), CK7 (-) and CDX2 (+). Its genome harboured 28 somatic non-silent mutations (27 missense and 1 nonsense) that included eight putative driver gene mutations catalogued in COSMIC database (KRAS, GNAS, ZBTB38, ENAM, HTR5A, BAI1, ADAMTS8 and RASA3). KRAS mutation as well as mutations in genes that antagonise RAS signalling (RASA3 and ADAMTS8) suggest that alterations in RAS signalling may play a role in its development. More importantly, the concurrent KRAS and GNAS hotspot mutations, and CK20 (+), CK7 (-) and CDX2 (+) expression strongly indicated its appendiceal origin. Our results indicate that next-generation sequencing combined with histological and immunohistochemical analyses may be a better strategy than the conventional analyses alone to identify the origin of a secondary tumour arising from a mature teratoma. Also, the data suggest that a PMP secondary to a primary ovarian mucinous tumour genome arising in the teratoma may recapitulate the mutational features of appendiceal mucinous tumours.