KAI1 C-terminal Interacting Tetraspanin Research Articles

A peptide interfering with the dimerization of oncogenic KITENIN protein and its stability suppresses colorectal tumour progression.

The stability of a protein, as well as its function and versatility, can be enhanced through oligomerization. KITENIN (KAI1 C‐terminal interacting tetraspanin) is known to promote the malignant progression of colorectal cancer (CRC). How KITENIN maintains its structural integrity and stability are largely unknown, however. Here we investigated the mechanisms regulating the stability of KITENIN with the aim of developing therapeutics blocking its oncogenic functions. We found that KITENIN formed a homo‐oligomeric complex and that the intracellular C‐terminal domain (KITENIN‐CTD) was needed for this oligomerization. Expression of the KITENIN‐CTD alone interfered with the formation of the KITENIN homodimer, and the amino acid sequence from 463 to 471 within the KITENIN‐CTD was the most effective. This sequence coupled with a cell‐penetrating peptide was named a KITENIN dimerization‐interfering peptide (KDIP). We next studied the mechanisms by which KDIP affected the stability of KITENIN. The KITENIN‐interacting protein myosin‐X (Myo10), which has oncogenic activity in several cancers, functioned as an effector to stabilize the KITENIN homodimer in the cis formation. Treatment with KDIP resulted in the disintegration of the homodimer via downregulation of Myo10, which led to increased binding of RACK1 to the exposed RACK1‐interacting motif (463–471 aa), and subsequent autophagy‐dependent degradation of KITENIN and reduced CRC cell invasion. Intravenous injection of KDIP significantly reduced the tumour burden in a syngeneic mouse tumour model and colorectal liver metastasis in an intrasplenic hepatic metastasis model. Collectively, our present results provide a new cancer therapeutic peptide for blocking colorectal liver metastasis, which acts by inducing the downregulation of Myo10 and specifically targeting the stability of the oncogenic KITENIN protein.

The lichen secondary metabolite atranorin suppresses lung cancer cell motility and tumorigenesis

Lichens are symbiotic organisms that produce various secondary metabolites. Here, different lichen extracts were examined to identify secondary metabolites with anti-migratory activity against human lung cancer cells. Everniastrum vexans had the most potent inhibitory activity, and atranorin was identified as an active subcomponent of this extract. Atranorin suppressed β-catenin-mediated TOPFLASH activity by inhibiting the nuclear import of β-catenin and downregulating β-catenin/LEF and c-jun/AP-1 downstream target genes such as CD44, cyclin-D1 and c-myc. Atranorin decreased KAI1 C-terminal interacting tetraspanin (KITENIN)-mediated AP-1 activity and the activity of the KITENIN 3′-untranslated region. The nuclear distribution of the AP-1 transcriptional factor, including c-jun and c-fos, was suppressed in atranorin-treated cells, and atranorin inhibited the activity of Rho GTPases including Rac1, Cdc42, and RhoA, whereas it had no effect on epithelial-mesenchymal transition markers. STAT-luciferase activity and nuclear STAT levels were decreased, whereas total STAT levels were moderately reduced. The human cell motility and lung cancer RT² Profiler PCR Arrays identified additional atranorin target genes. Atranorin significantly inhibited tumorigenesis in vitro and in vivo. Taken together, our results indicated that E. vexans and its subcomponent atranorin may inhibit lung cancer cell motility and tumorigenesis by affecting AP-1, Wnt, and STAT signaling and suppressing RhoGTPase activity.

Abstract 3530: KITENIN works as a fine regulator of ErbB4 expression in colorectal cancer tissues in addition to E3-ubiquitin ligase Nrdp1

Abstract Purpose: Understanding the complex biological functions of E3-ubiquitin ligases may facilitate the modulation of E3-ubiquitin ligases as a promising approach for the development of novel anticancer drugs. We recently identified that the KITENIN/ErbB4-Dvl2-c-Jun axis works as a novel unconventional downstream signal of epidermal growth factor in colorectal cancer (CRC) tissues and that the immunohistochemical expression of KITENIN/ErbB4 was highly expressed in tumor tissues from advanced CRC stage. However, the detailed mechanisms that explain the higher levels of ErbB4 in colon cancer tissues are largely unknown. Here we investigated whether E3-ubiquitin ligases participate in the operation of the KITENIN/ErbB4-Dvl2-c-Jun axis and in the maintenance of elevated KITENIN/ErbB4 complex in CRC. Results & Discussion: We found that Nrdp1, an E3-ligase for ErbB3/ErbB4, interacted with KITENIN (KAI1 C-terminal interacting tetraspanin) to form a functional KITENIN/ErbB4/Nrdp1 complex and is responsible for down-regulating Dvl2 within this complex. Interestingly, ErbB4 was resistant to degradation by Nrdp1 in KITENIN/Nrdp1-co-transfected CRC cells, and KITENIN bound to the C-terminal coiled-coil domain of Nrdp1. Chemical blockade of ErbB kinase did not block the action of EGF to increase in total/phospho-ErbB4 and phospho-ERK in KITENIN/ErbB4-cotransfected cells, whereas it blocked the action of EGF in ErbB4 alone-transfected CRC cells. In human CRC tissues, higher expressions of ErbB4 and KITENIN and lower expression of Dvl2 was observed in stage IV samples than in stage I, but a low level of Nrdp1 was expressed in both stages and it did not differ significantly by stage. These results indicated that Nrdp1 is necessary for the reduction in Dvl2 to generate c-Jun in the EGF-KITENIN/ErbB4-c-Jun axis, but more importantly, elevated KITENIN protects KITENIN-bound ErbB4 from Nrdp1-mediated degradation via physical collaboration between the KITENIN/ErbB4 complex and Nrdp1, but not via modulation of ErbB kinase activity. Thus, KITENIN functions in the maintenance of a higher expression level of ErbB4 in advanced CRC tissues, independent of ubiquitin-mediated degradation via Nrdp1. Conclusion: Our present findings add a new component to our understanding of the molecular events underlying the regulation of ErbB4 expression level in CRC tissues: KITENIN is also a fine regulator of ErbB4 expression in addition to E3-ubiquitin ligase Nrdp1. Citation Format: Jeong A Bae, Eun Gene Sun, Yoo-Seung Ko, Hui Jeong Choi, Chaeyong Jung, Kyung-Hwa Lee, Ik Joo Chung, Kyung-Sub Moon, Young Hyun Yu, Hyung-Ho Ha, Hangun Kim, Kyung Keun Kim. KITENIN works as a fine regulator of ErbB4 expression in colorectal cancer tissues in addition to E3-ubiquitin ligase Nrdp1 [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 3530. doi:10.1158/1538-7445.AM2017-3530

Abstract 4209: Inhibitory activity of lichen secondary metabolite, physciosporin, against lung cancer cell motility

Abstract Lichens produce various unique chemicals that can be used for pharmaceutical purposes. To screen for novel lichen secondary metabolites showing inhibitory activity against lung cancer cell motility, we tested acetone extracts of 13 lichen samples collected in Chile. Physciosporin, isolated from Pseudocyphellaria coriacea (Hook f. & Taylor) D.J. Galloway & P. James, was identified as an effective compound and showed significant inhibitory activity in migration and invasion assays against human lung cancer cells. Physciosporin treatment reduced both protein and mRNA levels of N-cadherin with concomitant decreases in the levels of epithelial-mesenchymal transition markers such as snail and twist. Physciosporin also suppressed KITENIN (KAI1 C-terminal interacting tetraspanin)-mediated AP-1 activity in both the absence and presence of epidermal growth factor stimulation. Quantitative real-time PCR analysis showed that the expression of the metastasis suppressor gene, KAI1, was increased while that of the metastasis enhancer gene, KITENIN, was dramatically decreased by physciosporin. Particularly, the activity of 3'-untranslated region of KITENIN was decreased by physciosporin. Moreover, Cdc42 and Rac1 activities were decreased by physciosporin. These results demonstrated that the lichen secondary metabolite, physciosporin, inhibits lung cancer cell motility through novel mechanisms of action. Citation Format: Yi Yang, Young Hyun Yu, Hyung-Ho Ha, Kyung-Hwa Lee, Kyung-Sub Moon, Kyung Keun Kim, Hangun Kim. Inhibitory activity of lichen secondary metabolite, physciosporin, against lung cancer cell motility [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 4209. doi:10.1158/1538-7445.AM2017-4209

KITENIN functions as a fine regulator of ErbB4 expression level in colorectal cancer via protection of ErbB4 from E3-ligase Nrdp1-mediated degradation.

Understanding the complex biological functions of E3-ubiquitin ligases may facilitate the development of mechanism-based anti-cancer drugs. We recently identified that the KITENIN/ErbB4-Dvl2-c-Jun axis works as a novel unconventional downstream signal of epidermal growth factor (EGF) in colorectal cancer (CRC) tissues. Here we addressed whether E3-ubiquitin ligases are required for operation of this axis. We found that Nrdp1, an E3-ligase for ErbB3/ErbB4, interacted with KITENIN (KAI1 C-terminal interacting tetraspanin) to form a functional KITENIN/ErbB4/Nrdp1 complex and is responsible for down-regulating Dvl2 within this complex. Interestingly, ErbB4 was resistant to degradation by Nrdp1 in KITENIN/Nrdp1-co-transfected CRC cells, and KITENIN bound to the C-terminal coiled-coil domain of Nrdp1. Chemical blockade of ErbB kinase did not block the action of EGF to increase in total/phospho-ErbB4 and phospho-ERK in KITENIN/ErbB4-cotransfected cells, whereas it blocked the action of EGF in ErbB4 alone-transfected CRC cells. In human CRC tissues, higher expressions of ErbB4 and KITENIN and lower expression of Dvl2 was observed in stage IV samples than in stage I, but a low level of Nrdp1 was expressed in both stages and it did not differ significantly by stage. These results indicated that Nrdp1 is necessary for the reduction in Dvl2 to generate c-Jun in the EGF-KITENIN/ErbB4-c-Jun axis, but more importantly, elevated KITENIN protects KITENIN-bound ErbB4 from Nrdp1-mediated degradation via physical collaboration between the KITENIN/ErbB4 complex and Nrdp1, but not via modulation of ErbB kinase activity. Thus, KITENIN functions in the maintenance of a higher expression level of ErbB4 in advanced CRC tissues, independent of ubiquitin-mediated degradation via Nrdp1. © 2016 Wiley Periodicals, Inc.

Abstract 5150: Identification of higher mRNA expression of both Kitenin and ErbB4 CYT-2 isoform as a molecular marker for the prediction of transition from colon adenoma to carcinoma

Abstract Purpose: The molecular events in the malignant progression of colon adenoma after loss of adenomatous polyposis coli (APC) are not fully understood. KITENIN (KAI1 C-terminal interacting tetraspanin) increases the invasiveness of colorectal cancer (CRC) cells and we recently identified a novel EGFR-independent oncogenic signal of EGF that works under co-expressed KITENIN and ErbB4. Here we tested whether elevated KITENIN and ErbB4 contributes to further progression of intestinal adenoma following APC loss. Results & Discussion: The intestinal tissues of villin-KITENIN transgenic mice in which villin-driven elevated KITENIN induced increased c-Jun expression exhibit mild epithelial cell proliferation but no epithelial lineage changes, compared with those of non-transgenic mice. Among the 4 ErbB4 isoforms, JM-a/CYT-2 and JM-b/CYT-2 exhibited the highest AP-1 activity when cells co-expressing KITENIN and each isoform were stimulated by EGF. Interestingly, predominant overexpression of ErbB4 CYT-2 isoform mRNA as well as increased EGFR expression were observed in intestinal adenoma of APCmin/+ mice making the microenvironment of activated EGF signaling. When we crossed villin-KITENIN mice with APCmin/+ mice, intestinal tumor tissues in the crossed mice showed the characteristics of early stage invading adenocarcinoma. In CRC patients, ErbB4-CYT-2 mRNA expression was significantly greater in tumor tissues than in normal adjacent tissues, but no differences in tumoral expression between the stages, and a positive correlation exists between KITENIN and ErbB4-CYT-2 mRNA expression. Thus, elevated expression of KITENIN and ErbB4-CYT-2 is newly identified as a factor that promotes the transition of colon adenoma to adenocarcinoma within an APC-loss-associated tumor microenvironment. Conclusion: Higher mRNA expression of both KITENIN and ErbB4-CYT-2 in colon adenoma tissues can be used as a molecular marker of the possible development of malignant transformation. Citation Format: Jeong A Bae, Eun Gene Sun, Yoo-Seung Ko, Hui Jeong Choi, Woo-Kyun Bae, Sang-Hee Cho, Ik Joo Chung, Kyung-Sub Moon, Young-Hyun Yu, Hyung-Ho Ha, Hangun Kim, Kyung Keun Kim. Identification of higher mRNA expression of both Kitenin and ErbB4 CYT-2 isoform as a molecular marker for the prediction of transition from colon adenoma to carcinoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 5150.

Elevated Coexpression of KITENIN and the ErbB4 CYT-2 Isoform Promotes the Transition from Colon Adenoma to Carcinoma Following APC loss.

The molecular events in the malignant progression of colon adenoma after loss of adenomatous polyposis coli (APC) are not fully understood. KITENIN (KAI1 C-terminal interacting tetraspanin) increases the invasiveness of colorectal cancer cells, and we identified a novel EGFR-independent oncogenic signal of EGF that works under coexpressed KITENIN and ErbB4. Here we tested whether elevated KITENIN and ErbB4 contribute to further progression of intestinal adenoma following APC loss. The intestinal tissues of villin-KITENIN transgenic mice in which villin-driven KITENIN expression induces increased c-Jun expression exhibit mild epithelial cell proliferation but no epithelial lineage changes compared with those of nontransgenic mice. Among the four ErbB4 isoforms, JM-a/CYT-2 and JM-b/CYT-2 exhibited the highest AP-1 activity when cells coexpressing KITENIN and each isoform were stimulated by EGF. Interestingly, predominant overexpression of the ErB4-CYT-2 mRNA as well as increased EGFR expression were observed in intestinal adenoma of APC(min/+) mice, which makes the microenvironment of activated EGF signaling. When we crossed villin-KITENIN mice with APC(min/+) mice, intestinal tumor tissues in the crossed mice showed the characteristics of early-stage invading adenocarcinoma. In patients with colorectal cancer, ErbB4-CYT-2 mRNA expression was significantly greater in tumor tissues than in normal adjacent tissues, but no significant differences in tumor tissue expression were found between different colorectal cancer stages. Furthermore, the mRNA expression of KITENIN and that of ErbB4-CYT-2 were positively correlated in human colorectal cancer tissue. Elevated coexpression of KITENIN and ErbB4-CYT-2 promotes the transition of colon adenoma to adenocarcinoma within an APC loss-associated tumor microenvironment.

Lichen Secondary Metabolite, Physciosporin, Inhibits Lung Cancer Cell Motility.

Lichens produce various unique chemicals that can be used for pharmaceutical purposes. To screen for novel lichen secondary metabolites showing inhibitory activity against lung cancer cell motility, we tested acetone extracts of 13 lichen samples collected in Chile. Physciosporin, isolated from Pseudocyphellaria coriacea (Hook f. & Taylor) D.J. Galloway & P. James, was identified as an effective compound and showed significant inhibitory activity in migration and invasion assays against human lung cancer cells. Physciosporin treatment reduced both protein and mRNA levels of N-cadherin with concomitant decreases in the levels of epithelial-mesenchymal transition markers such as snail and twist. Physciosporin also suppressed KITENIN (KAI1 C-terminal interacting tetraspanin)-mediated AP-1 activity in both the absence and presence of epidermal growth factor stimulation. Quantitative real-time PCR analysis showed that the expression of the metastasis suppressor gene, KAI1, was increased while that of the metastasis enhancer gene, KITENIN, was dramatically decreased by physciosporin. Particularly, the activity of 3’-untranslated region of KITENIN was decreased by physciosporin. Moreover, Cdc42 and Rac1 activities were decreased by physciosporin. These results demonstrated that the lichen secondary metabolite, physciosporin, inhibits lung cancer cell motility through novel mechanisms of action.

Abstract 4695: Role of KITENIN in malignant gliomas in relation to tumor invasiveness

Abstract Background: KAI1 C-terminal interacting tetraspanin (KITENIN) has been reported to promote tumor invasion and metastasis in various cancers. The aim of this study was to investigate the effect of KITENIN on biological behaviors in human gliomas and in mouse glioma models. Methods: KITENIN expression was examined using western blot, qRT-PCR and immunohistochemistry on human samples. KITENIN expression rate was compared in each histological grade, and survival rates were analyzed. Tumor invasiveness was investigated both in vitro and in vivo using stable cell lines after KITENIN-overexpression (GL261) and knock down (U251). Results: Expression of KITENIN tended to be stronger in high-grade gliomas than in low-grade gliomas by western blot & qRT-PCR on frozen human tumor samples and by immunohistochemistry on paraffin-embedded tissues as well. Proportions of strong KITENIN expression were 16.7%, 21.4%, 33.3%, and 56.8%, respectively, from grade I through IV (p=0.001). However, survival analysis using the Kaplan-Meier method did not reveal statistically significant difference between the high KITENIN expression group and the low expression group in terms of overall survival and progression free survival (p=0.55 and 0.807, respectively). In vitro assays revealed that genetic modulation of KITENIN was significantly related with tumor cell invasion & migration. Up-regulated KITENIN expression significantly affected the survival rate possibly due to increased invasiveness in orthotopic mouse glioma models. Conclusion: Strong KITENIN expression was more likely to be observed in high-grade gliomas and its up-regulation was associated with increased invasiveness supported by shorter survival rates in orthotopic mouse glioma models. Citation Format: Kyung-Hwa Lee, Kyung-Sub Moon, Eun-Jeong Ahn, Se-Jeong Oh, Sang-Hee Cho, Jae-Hyuk Lee, Shin Jung, Kyung Keun Kim. Role of KITENIN in malignant gliomas in relation to tumor invasiveness. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4695. doi:10.1158/1538-7445.AM2014-4695

KITENIN-targeting MicroRNA-124 Suppresses Colorectal Cancer Cell Motility and Tumorigenesis

MicroRNAs are increasingly implicated in the modulation of the progression of various cancers. We previously observed that KAI1 C-terminal interacting tetraspanin (KITENIN) is highly expressed in sporadic human colorectal cancer (CRC) tissues and hence the functional KITENIN complex acts to promote progression of CRC. However, it remains unknown that microRNAs target KITENIN and whether KITENIN-targeting microRNAs modulate CRC cell motility and colorectal tumorigenesis. Here, through bioinformatic analyses and functional studies, we showed that miR-124, miR-27a, and miR-30b negatively regulate KITENIN expression and suppress the migration and invasion of several CRC cell lines via modulation of KITENIN expression. Through in vitro and in vivo induction of mature microRNAs using a tetracycline-inducible system, miR-124 was found to effectively inhibit the invasion of CT-26 colon adenocarcinoma cells and tumor growth in a syngeneic mouse xenograft model. Constitutive overexpression of precursor miR-124 in CT-26 cells suppressed in vivo tumorigenicity and resulted in decreased expression of KITENIN as well as that of MYH9 and SOX9, which are targets of miR-124. Thus, our findings identify that KITENIN-targeting miR-124, miR-27a, and miR-30b function as endogenous inhibitors of CRC cell motility and demonstrate that miR-124 among KITENIN-targeting microRNAs plays a suppressor role in colorectal tumorigenesis.

An unconventional KITENIN/ErbB4-mediated downstream signal of EGF upregulates c-Jun and the invasiveness of colorectal cancer cells.

EGF-stimulated signaling via EGF receptor (EGFR) is important in colorectal tumorigenesis and drug targeting. However, anti-EGFR therapy is not effective in a subset of patients with colorectal cancer, suggesting that unidentified EGF-stimulated pathways might play roles in colorectal cancer. Previously, we identified KAI1 C-terminal interacting tetraspanin (KITENIN) as a metastasis-enhancing gene and found it to be highly expressed in sporadic colorectal cancer tissues. We recently found that EGF further increases KITENIN-induced elevated AP-1 activity. Here we attempted to clarify this novel EGF-stimulated molecular pathway and its roles in colorectal cancer. We analyzed how EGF modulates the downstream signaling pathway of oncogenic KITENIN in colorectal cancer cells. Biological alterations following EGF treatment were identified in KITENIN-overexpressed colorectal cancer cells with or without alteration of EGFR activity. We identified the KITENIN/ErbB4-Dvl2-c-Jun axis as a novel downstream signal of EGF that is switched on under elevated KITENIN conditions in an EGFR-independent manner. This unconventional EGF signal upregulates c-Jun and enhances invasion and anchorage-independent growth of colorectal cancer cells. In addition, tumor tissues from metastatic patients with colorectal cancer who showed initial poor responses to cetuximab/chemotherapy expressed higher levels of KITENIN than did responders to therapy. Our results highlight the role of an EGFR-independent EGF signal in mediating the invasiveness and tumorigenesis of colorectal cancer cells. This unconventional pathway might be related to the limited clinical efficacy of anti-EGFR agents in a subset of patients with colorectal cancer.

Abstract 4006: Biochemical characteristics of functional domain of KITENIN: Its implication in AP-1 signal activation and colorectal cancer cell motility

Abstract Background & aims: KITENIN (KAI1 C-terminal interacting tetraspanin) is not only a membrane-associated protein but also a functional protein promoting the invasiveness of colorectal cancer (CRC) cells. Recent studies about the mechanism of KITENIN function in the CRC cells indicate that KITENIN plays a pivotal role in tumor initiation and promotion through activating the activator protein-1 (AP-1) signaling. However, the contribution of each functional domain of KITENIN to AP-1 signaling is still unknown and the biochemical properties of C-terminal region of KITENIN were investigated. Methods: To compare the biochemical and functional properties of KITENIN deletion mutants with wild-type KITENIN, the various mutant constructs of C-terminal region (238-512 aa) were generated and being expressed in the 293T and Caco2 cells. AP-1 activity was measured via AP-1 luciferase reporter assays, and the cellular phenotypes of these cells expressing KITENIN mutants were examined via in vitro cell invasion and wound-healing assays. Results: KITENIN mutant with deletion of C-terminal 63 amino acids (DCKIT) markedly increased the AP-1 activity in contrast to other deletion mutants and wild-type KITENIN. Also, DCKIT increased the degradation of Dvl2 and stability of c-Jun, which are responsible for AP-1 activation by KITENIN. The C-terminal fragment of KITENIN (KICD, roughly 30 kDa) was generated and preferentially translocated to the nucleus after PMA treatment, but its functional significance is under investigation. A mutant construct of 408ALRA411-KITENIN was obtained by mutation of YXXΨ motifs, which directs the clathrin-dependent endocytosis of membrane-spanning proteins. This mutation did not influence the AP-1 activity, cell invasiveness, and cell migration by KITENIN but disrupted the interaction of KITENIN with Dvl2. Moreover, co-expression of this mutant with ErbB4 exhibited more attenuated AP-1 activity than that of forced expression of wild-type KITENIN and ErbB4. These results indicate that endocytosis of KITENIN and subsequent interaction with Dvl2 is essential to activating AP-1 signal and modulating cell motility by KITENIN. Conclusion: These biochemical properties of deletion mutants of KITENIN suggest that the C-terminal region of KITENIN is an important component for modulating AP-1 signal and CRC cell motility by KITENIN. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4006. doi:1538-7445.AM2012-4006

Intravenous KITENIN shRNA Injection Suppresses Hepatic Metastasis and Recurrence of Colon Cancer in an Orthotopic Mouse Model

KITENIN (KAI1 C-terminal interacting tetraspanin) promotes invasion and metastasis in mouse colon cancer models. In the present study, we evaluated the effects of KITENIN knockdown by intravenous administration of short hairpin RNAs (shRNAs) in an orthotopic mouse colon cancer model, simulating a primary or adjuvant treatment setting. We established orthotopic models for colon cancer using BALB/c mice and firefly luciferase-expressing CT-26 (CT26/Fluc) cells. Tumor progression and response to therapy were monitored by bioluminescence imaging (BLI). In the primary therapy model, treatment with KITENIN shRNA substantially delayed tumor growth (P = 0.028) and reduced the incidence of hepatic metastasis (P = 0.046). In the adjuvant therapy model, KITENIN shRNA significantly reduced the extent of tumor recurrence (P = 0.044). Mice treated with KITENIN shRNA showed a better survival tendency than the control mice (P = 0.074). Our results suggest that shRNA targeting KITENIN has the potential to be an effective tool for the treatment of colon cancer in both adjuvant and metastatic setting.

KITENIN increases invasion and migration of mouse squamous cancer cells and promotes pulmonary metastasis in a mouse squamous tumor model

KAI1 C-terminal interacting tetraspanin (KITENIN) is reported to promote metastasis in mouse colon cancer models. We investigated the role of KITENIN on the progression of squamous cell carcinoma (SCC). In a preliminary clinical study using resected tissues from head and neck SCC patients, KITENIN was highly expressed in tumors and metastatic lymph nodes, while KAI1 was more increased in adjacent mucosa than in tumor. KITENIN-transfected mouse squamous cancer (SCC VII/KITENIN) cells showed significantly higher invasion, migration, and proliferation than empty vector-transfected cells. In syngeneic mouse squamous tumor models, more increased tumor volume and enhanced lung metastasis were found in SCC VII/KITENIN cells-injected mice. Thus, KITENIN increases invasion and migration of squamous cancer cells and thereby promotes distant metastasis in mouse squamous tumor models.