CDX2 Is a Prognostic Biomarker for Unresectable Metastatic Colorectal Cancer

BACKGROUND/AIM

Colorectal cancer (CRC) with reduced expression of the homeobox transcription factor CDX2, a master gene essential for the development and maintenance of the intestinal tract, is known as a poor prognosis subtype of CRC. The recurrence rate is high in patients with CDX2^low CRC. However, the prognostic significance of CDX2 in advanced CRC is unclear. This study aimed to elucidate the prognostic significance of CDX2 in unresectable metastatic CRC (mCRC).

PATIENTS AND METHODS

Twenty-nine patients with unresectable mCRC who underwent primary site resection at the Kobe University Hospital during a 6-year period from January 2008 to January 2015 were included. The tissues from those patients were immunohistochemically stained with anti-CDX2 antibody (clone: CDX2-88). The patients were divided into CDX2^high CRC group and CDX2^low CRC group and their prognoses were analyzed.

RESULTS

There were no clear differences in background between the two groups. A low CDX2 expression was associated with reduced overall survival (37.67 months vs. 25.32 months, p=0.03) and tended to associate with reduced progression-free survival (17.4 months vs. 12.9 months, p=0.37). Two patients received chemotherapy after resection of the primary lesion and obtained pathological complete response.

CONCLUSION

CDX2 expression might be a possible prognostic biomarker for unresectable mCRC.

Upregulation of BMI1-suppressor miRNAs (miR-200c, miR-203) during terminal differentiation of colon epithelial cells

BACKGROUND

MicroRNAs (miRNAs) are key regulators of stem cell functions, including self-renewal and differentiation. In this study, we aimed to identify miRNAs that are upregulated during terminal differentiation in the human colon epithelium, and elucidate their role in the mechanistic control of stem cell properties.

METHODS

"Bottom-of-the-crypt" (EPCAM⁺/CD44⁺/CD66a^low) and "top-of-the-crypt" (EPCAM⁺/CD44^neg/CD66a^high) epithelial cells from 8 primary colon specimens (6 human, 2 murine) were purified by flow cytometry and analyzed for differential expression of 335 miRNAs. The miRNAs displaying the highest upregulation in "top-of-the-crypt" (terminally differentiated) epithelial cells were tested for positive correlation and association with survival outcomes in a colon cancer RNA-seq database (n = 439 patients). The two miRNAs with the strongest "top-of-the-crypt" expression profile were evaluated for capacity to downregulate self-renewal effectors and inhibit in vitro proliferation of colon cancer cells, in vitro organoid formation by normal colon epithelial cells and in vivo tumorigenicity by patient-derived xenografts (PDX).

RESULTS

Six miRNAs (miR-200a, miR-200b, miR-200c, miR-203, miR-210, miR-345) were upregulated in "top-of-the-crypt" cells and positively correlated in expression among colon carcinomas. Overexpression of the three miRNAs with the highest inter-correlation coefficients (miR-200a, miR-200b, miR-200c) associated with improved survival. The top two over-expressed miRNAs (miR-200c, miR-203) cooperated synergistically in suppressing expression of BMI1, a key regulator of self-renewal in stem cell populations, and in inhibiting proliferation, organoid-formation and tumorigenicity of colon epithelial cells.

CONCLUSION

In the colon epithelium, terminal differentiation associates with the coordinated upregulation of miR-200c and miR-203, which cooperate to suppress BMI1 and disable the expansion capacity of epithelial cells.

Simple Cancer Stem Cell Markers Predict Neoadjuvant Chemotherapy Resistance of Esophageal Squamous Cell Carcinoma

BACKGROUND/AIM

Cancer stem cells (CSCs) contribute to resistance against neoadjuvant chemotherapy (NAC) in esophageal squamous cell carcinoma (ESCC). We conducted a retrospective observational study for the relationship between the expression levels of CSC markers in biopsy specimens prior to 5-fluorouracil plus cisplatin (FP)-NAC and the pathological responses.

PATIENTS AND METHODS

We included 171 patients with ESCC who underwent the FP-NAC followed by radical resection. Biopsy specimens prior to the FP-NAC were obtained and immunochemically stained for CD44, CD133, and CD24.

RESULTS

The biopsy specimens of the non-responders had the CD44^high/CD24^low expression at high levels, which was found as an independent predictor of not only FP-NAC resistance but also poor overall survival by multivariate analyses.

CONCLUSION

CD44^high/CD24^low expression in the biopsy specimens prior to FP-NAC may be a predictor of FP-NAC resistance and poor prognosis of ESCC patients.

Treatment Strategy for Rectal Cancer Patients With Inguinal Lymph Node Metastasis

BACKGROUND/AIM

To investigate the impact of inguinal lymph node dissection (ILND) following neoadjuvant chemoradiotherapy (NACRT) for rectal cancer patients with ILN metastasis.

PATIENTS AND METHODS

Forty-three patients with rectal cancer underwent NACRT followed by curative surgery between January 2005 and December 2016. Seven patients underwent ILND after NACRT for clinically-positive ILN metastasis (ILND (+) group), while the remaining 36 did not receive ILND for clinically negative ILN metastasis (ILND (-) group). Their outcomes were retrospectively analyzed.

RESULTS

Only one patient in the ILND (+) group had a local recurrence at six years after surgery. The 5-year recurrence-free survival was 100% and 65.4% in the ILND (+) and ILND (-) groups, respectively (p=0.09), and the 5-year overall survival was 100% and 83.2%, respectively (p=0.32).

CONCLUSION

ILND following NACRT seems effective for rectal cancer patients with ILN metastasis.

miR-221 Targets QKI to Enhance the Tumorigenic Capacity of Human Colorectal Cancer Stem Cells

miRNAs are key players in the integrated regulation of cellular processes and shape many of the functional properties that define the "cancer stem cell" (CSC) phenotype. Little is known, however, about miRNAs that regulate such properties in human colorectal carcinoma. In this study, we compared the expression levels of 754 miRNAs between paired samples of EpCAM⁺/CD44⁺ cancer cells (enriched in CSCs) and EpCAM⁺/CD44^neg cancer cells (with CSC depletion) sorted in parallel from human primary colorectal carcinomas and identified miR-221 as the miRNA that displayed the highest level of preferential expression in EpCAM⁺/CD44⁺ cancer cells. High levels of miR-221 expression were associated with Lgr5⁺ cells in mouse colon crypts and reduced survival in patients with colorectal carcinoma. Constitutive overexpression of miR-221 enhanced organoid-forming capacity of both conventional colorectal carcinoma cell lines and patient-derived xenografts (PDX) in vitro. Importantly, constitutive downregulation of miR-221 suppressed organoid-forming capacity in vitro and substantially reduced the tumorigenic capacity of CSC populations from PDX lines in vivo. Finally, the most abundant splicing isoform of the human Quaking (QKI) gene, QKI-5, was identified as a functional target of miR-221; overexpression of miR-221-reduced QKI-5 protein levels in human colorectal carcinoma cells. As expected, overexpression of QKI-5 suppressed organoid-forming capacity in vitro and tumorigenic capacity of colorectal carcinoma PDX cells in vivo. Our study reveals a mechanistic link between miR-221 and QKI and highlights their key role in regulating CSC properties in human colorectal cancer. SIGNIFICANCE: These findings uncover molecular mechanisms underlying the maintenance of cancer stem cell properties in colon cancer.Graphical Abstract: http://cancerres.aacrjournals.org/content/canres/79/20/5151/F1.large.jpg.

Organoid Culture of Human Cancer Stem Cells

Organoid culture is a three-dimensional culture method that enables ex vivo analysis of stem cell behavior and differentiation. This method is also applicable to the studies on stem cell characters of human cancer stem cells. The components of organoid culture include Matrigel® and a culture medium containing growth factor cocktails that mimic the microenvironments of organ stem cell niches. Here, we describe the basic methods for the organoid culture of dissociated or FACS-sorted human cancer stem cells. Then, we introduce a method to dissociate the organoids for serial passage and propagation.

Recent advances of neoadjuvant chemoradiotherapy in rectal cancer: Future treatment perspectives

Neoadjuvant chemoradiotherapy (nCRT) has been widely used as a multidisciplinary approach for stage II/III rectal cancer. However, its safety and efficacy are controversial because previous studies have shown conflicting outcomes. The present review aimed to elucidate the benefits and limitations of nCRT for patients with rectal cancer. Future perspectives of nCRT are also described. No recent randomized trials have been able to show a survival benefit, although many studies have demonstrated good local control with the use of fluoropyrimidine (e.g. 5-fluorouracil [FU] or capecitabine)-based nCRT. Addition of oxaliplatin (OX) to FU-based nCRT might improve overall survival by preventing distant metastasis, as shown in recent meta-analyses. However, control of adverse effects is an important concern with this treatment. New treatment strategies such as nonoperative management (watch and wait policy) and total neoadjuvant therapy (TNT) are promising, but the establishment of reliable diagnostic methods of metastasis is essential. Development of new biomarkers is also necessary to select patients who are more likely to benefit from nCRT.

Laparoscopic ileocecal resection can be applied for appendiceal cancer with an ileal fistula: A case report

INTRODUCTION

Primary appendiceal cancer with fistula formation is extremely rare. We report a case of a patient with appendiceal cancer invading the ileum who underwent successful laparoscopic ileocecal resection.

PRESENTATION OF CASE

A 76-year-old man who presented with fever and abdominal pain was diagnosed with acute appendicitis and received antibiotics at a local hospital. After a few days, he was referred to our hospital because of an abnormality found in the colonoscopy, which was an oozing ulcer in the terminal ileum. Laparoscopic ileocecal resection was performed with a preoperative diagnosis of ileal cancer. The tumor adhered to the right internal inguinal ring. We dissected the right spermatic cord involved in the tumor. The resected specimen revealed a fistula between the appendiceal orifice and ileac ulcer. Histopathological examination revealed a well differentiated tubular adenocarcinoma. We made the diagnosis of appendiceal cancer with an ileal fistula because the ileal ulcer was derived from the appendiceal site.

DISCUSSION

Most cases of appendiceal cancer with a fistula undergo laparotomy, but in selected cases, laparoscopic resection should be considered a feasible, safe, and curative procedure. Our patient underwent laparoscopic ileocecal resection, whereby the tumor and other organs with invasion were resected successfully with a negative surgical margin.

CONCLUSION

This is the first case report of appendiceal cancer with an ileal fistula successfully treated with laparoscopic resection. Laparoscopic ileocecal resection can be applied for appendiceal cancers with a fistula by experienced surgeons with careful consideration.

Abstract 4572: The induction of PD-L1 positive immune cells and CD8-positive T lymphocytes by neoadjuvant chemoradiotherapy for rectal cancer

Background; Immunotherapy, particularly blockade of programmed cell death-1 (PD-1) has shown unprecedented success in treating various types of cancers. In recent clinical trial of PD-1 blockade, clinicians focused on the characteristics of metastatic colorectal cancer patients with MSI-H (microsatellite instability- high) tumor associated with somatic hypermutation and confirmed a benefit of this immunotherapy in the disease. On the other hand, for MSS patients who account for most of colorectal cancer patient, new immunological strategies are needed. From before, radiation therapy is expected as an approach to overcome this relative resistance across colorectal cancers. Some reports on the relationship between tumor immunological microenvirment and irradiation have also been reported. Based on these findings, we examined a tumor immunological microenvironment of rectal cancer performed by chemoradiotherapy with immunohistochemical analysis of biopsy and surgical specimens.

Methods; From January 2005 to December 2016, 77 lower rectal cancer cases with cT3-4 or cN (+) were surgically treated in our institution and enrolled and 68 were eligible for this study. Immunohistochemistry of PD-L1, CD8, and CD163 was performed on biopsy specimens and surgically resected specimens of all cases, and their changes of expression before and after treatment were examined. We also examined the relationship between the expression of these tumor immunity-related factors and clinicopathological factors and prognosis.

Results; There were 44 cases in which NACRT was performed (NA group) and 24 cases in which surgery alone was performed (S group). In the S group, there was no significant change in the infiltration of PD-L1 positive immune cells (PD-L1+IC) nor CD8 positive tumor-infiltrating lymphocytes (CD8+TIL) before and after treatment, but in the NA group, the infiltrations of them were significantly increased (p = 0.038 and p = 0.0027, respectively). Although no PD-L1 positive tumor cells (PD-L1+TC) were observed in the biopsy specimens, there were 5 cases in which PD-L1+TC were observed in the surgically resected specimens, and all of which were cases of NACRT group (not significant). In multivariate analysis, low infiltration of PD-L1+IC (p = 0.033) was revealed as poor prognostic factor in overall survival, and low infiltration of PD-L1+IC (p = 0.041) and CD8+TIL (p = 0.0094) were identified as poor prognostic factors in disease-free survival.

Conclusion; The infiltration of PD-L1+IC and CD8+TIL was induced by NACRT. The presence of PD-L1+IC in the tumor tissue was revealed to improve the prognosis of rectal cancer. In NACRT for rectal cancer, PD-1 inhibitor combination therapy should be introduced to tumors with PD-L1 positive IC.

Citation Format: Kimihiro Yamashita, Akio Nakagawa, Tomoko Tanaka, Akira Arimoto, Eiji Fukuoka, Yutaka Sugita, Junko Mukohyama, Piero Dalerba, Hiroshi Hasegawa, Takeru Matsuda, Satoshi Suzuki, Yoshihiro Kakeji. The induction of PD-L1 positive immune cells and CD8-positive T lymphocytes by neoadjuvant chemoradiotherapy for rectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4572.

Abstract 488: Epigenetic regulation of colorectal cancer stem cells by the miR-221/QKI5 axis

Colorectal cancer stem cells (CSCs) have extensive abilities to initiate tumor formation, and are responsible for the progression and metastasis of colorectal cancers. MicroRNAs (miRNAs) are non-coding RNAs of 18-24 nucleotides that post-transcriptionally regulate expression of multiple genes by targeting their 3'untranslated regions (UTRs). miRNAs regulate various biological processes, and function as important regulators of CSC properties.

miR-221 is one of the oncogenic miRNAs frequently upregulated in human cancers including colorectal cancer. Previous studies have shown that miR-221 enhances proliferation, migration, and invasion of cancer cells. However, the role of miR-221 in human colorectal CSCs is not fully elucidated. In this study, we analyzed the colorectal CSCs directly isolated from the surgical specimens of colorectal cancer patients to explore the role of miR-221 in CSCs.

Expression profile of 754 miRNAs in the CD44+/EpCAM+ CSC and non-tumorigenic cancer cell (NTC) populations was analyzed by multiplex semi-quantitative PCR. Prognostic impact of miR-221 expression in CSCs was analyzed using the TCGA database. Target genes of miR-221 were validated by luciferase reporter assays and Western blot experiments. The roles of miR-221 and its target gene QKI-5 in colorectal CSCs were evaluated by organoid and xenotransplantation assays.

Comparison of the expression levels of 754 miRNAs in the CSCs and NTCs resulted in the identification of 10 miRNAs upregulated or downregulated in CSCs compared to NTCs. Among them, miR-221 was most highly expressed in CSCs and its expression level was very low in NTCs and human normal colon epithelial cells of human colorectal cancer specimens (n=6, p<0.05). The estimated 5-year overall survival rate for miR-221high patients (n=177) was significantly lower than miR-221low ones (n=116) in TCGA dataset (54.6% vs. 73.6%; p<0.001). The TNM stages at diagnosis were not significantly associated with the expression level of miR-221. In a multivariate analysis, miR-221 expression were significantly associated with overall survival (p=0.009). miR-221 targeted an RNA binding protein (RBP) QKI-5 and suppressed its expression. Knockdown of miR-221 in human colorectal cancer patient-derived xenograft cells suppressed the organoid formation in vitro in a QKI-5-suppression-dependent manner, and tumor formation initiated by colorectal CSCs in vivo (n=6, p=0.015 ).

Our results suggest that the miR-221/QKI5 axis plays important roles in the regulation of CSC properties in human colorectal cancers. Because miR-221 was preferentially and highly upregulated in human colorectal CSCs, but not in normal stem/progenitor cells, it is possible that miR-221 will be a biomarker that reflects amount and/or activity of CSCs in colorectal cancers and an attractive target to selectively attach colorectal CSCs by avoiding damages on their normal counterparts.

Citation Format: Junko Mukohyama, Yohei Shimono, Piero Dalerba, Taichi Isobe, Qingjiang Hu, Debashis Sahoo, Naoki Shibuya, Hironobu Minami, Koshi Mimori, Yoshihiro Kakeji, Akira Suzuki. Epigenetic regulation of colorectal cancer stem cells by the miR-221/QKI5 axis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 488.

Evaluation of the risk of lymphomagenesis in xenografts by the PCR-based detection of EBV BamHI W region in patient cancer specimens

Establishment of patient-derived tumor xenografts (PDXs) is hampered by lymphomagenesis mostly caused by the latently-infected Epstein-Barr virus (EBV) contained in patient cancer tissues. However, the character of patient tissues that result in lymphomagenesis after xenotransplantation is not elucidated. In this study, we analyzed the patient colorectal cancer (CRC) tissues and the PDXs established by their xenotransplantation. We found that 2 of 9 (22%) PDX tumors were EBV-associated human diffuse large B cell lymphoma which was formed by clonal proliferation of human B-cell lymphocytes, were strongly positive for EBER-ISH, and were classified as type III latency. Expression of EBV genes and RNAs, such as EBNAs, LMP1, EBER and EBV-associated microRNAs in patient CRC tissues were unlikely to be associated with lymphomagenesis in PDXs. In contrast, the positive PCR-based amplification of BamHI W region, a major internal repeat in EBV genome, in the patient CRC tissues was correlated with lymphomagenesis in PDXs. These results suggest that the detection of the EBV BamHI W region in the patient surgical specimens will be an effective way to predict the risk of lymphomagenesis in PDXs before xenotransplantation.

Roles of microRNAs and RNA-Binding Proteins in the Regulation of Colorectal Cancer Stem Cells

Colorectal cancer stem cells (CSCs) are responsible for the initiation, progression and metastasis of human colorectal cancers, and have been characterized by the expression of cell surface markers, such as CD44, CD133, CD166 and LGR5. MicroRNAs (miRNAs) are differentially expressed between CSCs and non-tumorigenic cancer cells, and play important roles in the maintenance and regulation of stem cell properties of CSCs. RNA binding proteins (RBPs) are emerging epigenetic regulators of various RNA processing events, such as splicing, localization, stabilization and translation, and can regulate various types of stem cells. In this review, we summarize current evidences on the roles of miRNA and RBPs in the regulation of colorectal CSCs. Understanding the epigenetic regulation of human colorectal CSCs will help to develop biomarkers for colorectal cancers and to identify targets for CSC-targeting therapies.

Discordance of MCM7 mRNA and its Intronic MicroRNA Levels Under Hypoxia

BACKGROUND

Intronic microRNAs (miRNAs) are considered to be transcribed using their host gene promoter. However, about one third of intronic miRNAs are predicted to have independent promoter elements.

MATERIALS AND METHODS

Human breast cancer cells were cultured under normoxia or hypoxia, and expression levels of intronic miR-106b-25 cluster miRNAs and their host gene minichromosome maintenance complex component 7 (MCM7) transcripts were analyzed by semi-quantitative polymerase chain reaction. The putative promoter element of miR-106b-25 cluster was analyzed by chromatin immunoprecipitation and luciferase assays.

RESULTS

Exposure to hypoxia reduced the expression of MCM7 mRNA and a primary transcript of miR-106b-25 cluster, but did not affect that of mature miRNAs. The putative promoter element of miR-106b-25 cluster was not bound by hypoxia-inducible factor 1-alpha (HIF1-α), and was not activated under hypoxia.

CONCLUSION

Maintenance of miR-106b-25 cluster miRNA levels under hypoxia was not caused by the activation of an independent promoter element.

Abstract 2890: MicroRNA-mediated upregulation of the WNT signaling activities in human breast cancer stem cells

The canonical WNT signaling plays a critical role in many adult stem cells, including those of the breast and intestine. The fact that the canonical WNT signaling is implicated in both stem cell self-renewal and cancer suggests that normal physiological regulator of stem cell functions might be “hijacked” in cancer. Adenomatous polyposis coli (APC) is a component of the destruction complex that destabilizes β-catenin and suppresses the activity of the canonical WNT signaling.

MicroRNAs (miRNAs) are important regulators of stem cell functions. We have previously reported a set of 37 miRNAs that are upregulated or downregulated in human breast cancer stem cells (BCSCs, a CD44+CD24-/lowlineage- population of human breast cancer cells) as compared to non-tumorigenic breast cancer cells (NTCs). Among them, miR-200c targets BMI1 that is a critical regulator of the stem cell maintenance, and strongly impairs the functions of human BCSCs in vivo.

In this study, we compared the expression profiles of miRNAs, mRNAs and proteins between BCSCs and NTCs isolated from the patient specimens of human breast cancers and patient-derived tumor xenografts (PDXs) established by their transplantation. Luciferase assays were performed using the plasmid in which the 3’UTR region of candidate mRNA was cloned downstream of a luciferase minigene. The effect of miRNAs on the activity of WNT signaling was evaluated using a TCF reporter plasmid. Finally, the abilities to form organoids and to form tumors in immunodeficient mice were evaluated using the human BCSCs infected with the miRNA inhibitor expressing lentivirus.

We found that miR-142 was highly upregulated in BCSCs, but was hardly expressed in NTCs in the patient breast cancer specimens. We confirmed that miR-142 targeted the sequence within the 3’UTR of APC mRNA and suppressed APC protein expression. Accordingly, miR-142 activated the canonical WNT signaling pathway in an APC-suppression dependent manner. The results of mRNA and protein expression profiling of the BCSCs isolated from human breast cancer PDXs suggested that the canonical WNT signaling was activated in BCSCs. Finally, inhibition of miR-142 in the BCSCs suppressed the tumor growth in vivo.

These results suggest that the miR-142, a miRNA frequently upregulated in human BCSCs, could provide at least a part of the molecular mechanism for aberrant activation of the canonical WNT signaling in breast cancer in which APC mutations are much less frequent than colon cancer.

Citation Format: Yohei Shimono, Taichi Isobe, Andrei Turtoi, Junko Mukohyama, Toru Mukohara, Akira Suzuki, Vincent Castronovo, Hironobu Minami. MicroRNA-mediated upregulation of the WNT signaling activities in human breast cancer stem cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2890. doi:10.1158/1538-7445.AM2017-2890

Abstract 4822: Detection of EBV BamHI W region in surgical cancer specimen is a useful method to evaluate the risk of lymphomagenesis in patient-derived tumor xenografts

Patient-derived tumor xenografts (PDXs) established by xenotransplantation of surgically-resected human cancer specimens are an attractive model to analyze the character of cancer cells within the patient cancer tissues. However, establishment of PDX is occasionally hampered by lymphomagenesis.

Lymphomagenesis in the PDX has been observed in the xenotransplantation of several types of cancers, such as lung, liver, gastric, bladder, breast, prostate, and colorectal cancers. Lymphomagenesis in the PDX is caused by the proliferation of the EBV-infected lymphocytes under insufficient immunosurveillance in the immunodeficient mice. However, it is still difficult to predict lymphomagenesis before xenotransplantation.

In this study, we analyzed the expression of EBV-related genes in the 15 surgical specimens of the consented colorectal cancer (CRC) patients and the PDXs established by their xenotransplantation. The CRC specimens and the established PDX tumors were histologically examined. Then, the specimens were immunohistochemically stained with anti-CD3 and CD20 antibodies. The presence of EBV was histologically evaluated by EBER in situ. The expression levels of EBV-related genes, such as EBNAs, LMP1, EBER, BamHI W region and EBV-associated microRNAs, were evaluated using the genomic DNA and mRNAs prepared from the CRC specimens and the established PDX tumors.

Nine PDXs were established by the xenotransplantation. Histological examination showed that 7 of 9 (78%) PDX recapitulated histopathological characteristics of the patient CRC tissues. However, 2 of 9 (22%) PDXs exhibited the morphological characteristics of EBV-associated human diffuse large B cell lymphoma (DLBCL). Then, we confirmed that lymphoma was formed by clonal proliferation of human B-cell lymphocytes, and strongly positive for EBER. We investigated whether the expression of EBV-related genes in the patient specimen is associated with lymphomagenesis in the PDXs. Expression of EBV genes and RNAs in patient CRC tissues were not clearly associated with lymphomagenesis in the PDXs. BamHI W region is a major internal repeat in EBV genome and the PCR amplification of this region is useful to evaluate the presence and amount of EBV. When the EBV BamHI W region was detectable in the patient specimens, the transplantation of the samples resulted in lymphomagenesis in 2 out of 3 patient cancer specimens. In contrast, when this region was undetectable, no patient cancer specimens resulted in lymphomagenesis (0 out of 7 patient cancer specimens).

These results suggest that the amount and/or presence of EBV itself in the patient cancer specimens is one of the factors that are associated with lymphomagenesis in the PDXs. Therefore, the PCR amplification of EBV BamHI W region is an attractive method to evaluate the risk of lymphomagenesis before xenotransplantation.

Citation Format: Junko Mukohyama, Dai Iwakiri, Yoh Zen, Toru Mukohara, Hironobu Minami, Yoshihiro Kakeji, Yohei Shimono. Detection of EBV BamHI W region in surgical cancer specimen is a useful method to evaluate the risk of lymphomagenesis in patient-derived tumor xenografts [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4822. doi:10.1158/1538-7445.AM2017-4822

Effect of Xenotransplantation Site on MicroRNA Expression of Human Colon Cancer Stem Cells

BACKGROUND

Cancer stem cells (CSCs) have a high tumorigenic ability to form patient-derived tumor xenografts (PDXs). PDXs are an attractive pre-clinical model, but gene expression and biological behavior of cancer cells in the tumor will change during establishment and passage of PDXs.

MATERIALS AND METHODS

Human colon cancer PDX was established and passaged either subcutaneously or orthotopically into the murine intestine. Histology and flow cytometric profile of the surgical specimen and the PDX were analyzed. CSCs were then isolated from the tumors and their microRNA (miRNA) expression was analyzed by semi-quantitative polymerase chain reaction.

RESULTS

The surgical specimens and PDXs were histologically similar. The size of CSC population increased and expression of miRNAs in CSCs changed in the passaged PDXs. Expression of oncogenic miRNAs was highly up-regulated in the CSCs of the orthotopically passaged PDXs.

CONCLUSION

The xenotransplantation site and the number of tumor passages affect the miRNA expression of human colon CSCs.

MicroRNA Regulation of Human Breast Cancer Stem Cells

MicroRNAs (miRNAs) are involved in virtually all biological processes, including stem cell maintenance, differentiation, and development. The dysregulation of miRNAs is associated with many human diseases including cancer. We have identified a set of miRNAs differentially expressed between human breast cancer stem cells (CSCs) and non-tumorigenic cancer cells. In addition, these miRNAs are similarly upregulated or downregulated in normal mammary stem/progenitor cells. In this review, we mainly describe the miRNAs that are dysregulated in human breast CSCs directly isolated from clinical specimens. The miRNAs and their clusters, such as the miR-200 clusters, miR-183 cluster, miR-221-222 cluster, let-7, miR-142 and miR-214, target the genes and pathways important for stem cell maintenance, such as the self-renewal gene BMI1, apoptosis, Wnt signaling, Notch signaling, and epithelial-to-mesenchymal transition. In addition, the current evidence shows that metastatic breast CSCs acquire a phenotype that is different from the CSCs in a primary site. Thus, clarifying the miRNA regulation of the metastatic breast CSCs will further advance our understanding of the roles of human breast CSCs in tumor progression.

[Effect of Natural Killer Cell Infiltration on the Growth of Breast Cancer Patient-Derived Tumor Xenografts]

Natural killer (NK) cells, a component of the innate immunity, play important roles in tumor suppression. In this study, three human breast cancer patient-derived tumor xenografts (PDXs), established by the transplantation of surgical specimens, were passaged in immunodeficient NOD/SCID mice or NSG mice, that further lacks NK cell activity. The intensity of the relative growth suppression between NOD/SCID and NSG mice was clearly different depending on the PDX lines, and it was associated with the intensities of the CD49b-positive NK cell infiltration in the PDX tumor tissues. However, no obvious association was observed between the mRNA expression levels of the NK cell ligands in the PDX tumor cells and the intensity of NK cell infiltration into the PDX tumors. These results suggest that the suppressive effect of NK cells on the growth of breast cancer PDX is highly variable depending on the PDX lines. Further studies are needed to elucidate the molecular mechanism of NK cell infiltration in PDX tumors.

[Breast cancer stem cell research utilizing clinical specimens]

The existence of cancer stem cells in solid tumors was first reported in 2003 based on the analyses of human breast cancers. Analyses of clinical specimens are especially important for the advancement of human cancer stem cell research. For example, the analyses of breast cancer stem cells directly isolated from human breast cancer specimens identified the microRNAs that are involved in the regulation of human breast cancer stem cells. In addition, human breast cancer xenograft is an attractive model to analyze cancer stem cells, as well as cancer metastases that have profound effect on the long-term survival of breast cancer patients. We will present the current status of human breast cancer stem cell research that utilizes clinical specimens.