5584

PRKCI

protein kinase C, iota;PRKCI;protein kinase C, iota

PRKC-lambda/iota|aPKC-lambda/iota|atypical protein kinase C-lambda/iota|protein kinase C iota type

3q26.3

protein-coding

Dissemination of carcinoma cells requires the pericellular degradation of the extracellular matrix, which is mediated by membrane type 1-matrix metalloproteinase (MT1-MMP). In this article, we report a co-up-regulation and colocalization of MT1-MMP and atypical protein kinase C iota (aPKCiota) in hormone receptor-negative breast tumors in association with a higher risk of metastasis. Silencing of aPKC in invasive breast-tumor cell lines impaired the delivery of MT1-MMP from late endocytic storage compartments to the surface and inhibited matrix degradation and invasion. We provide evidence that aPKCiota, in association with MT1-MMP-containing endosomes, phosphorylates cortactin, which is present in F-actin-rich puncta on MT1-MMP-positive endosomes and regulates cortactin association with the membrane scission protein dynamin-2. Thus, cell line-based observations and clinical data reveal the concerted activity of aPKC, cortactin, and dynamin-2, which control the trafficking of MT1-MMP from late endosome to the plasma membrane and play an important role in the invasive potential of breast-cancer cells.

BACKGROUND & OBJECTIVE: Studies showed that the abnormal expression of atypical protein kinase C iota subtype (aPKC-iota) and E-cadherin plays an important role in tumor genesis and progression. This study was to investigate the expression of aPKC-iota and E-cadherin in cholangiocarcinoma, and analyze molecular mechanisms of the invasion and metastasis of cholangiocarcinoma. METHODS: The expression of aPKC-iota and E-cadherin in 9 specimens of benign bile duct tissues and 35 specimens of cholangiocarcinoma was detected by EnVision immunohistochemistry, and their correlations to the clinicopathologic characteristics and invasion of cholangiocarcinoma were analyzed. RESULTS: The positive rate of aPKC-iota was significantly higher in cholangiocarcinoma than in benign bile duct tissues (68.6% vs. 11.1%, P = 0.006), while the positive rate of E-cadherin was significantly lower in cholangiocarcinoma than in benign bile duct tissues (37.1% vs. 88.9%, P = 0.016). aPKC-iota expression was negatively correlated to E-cadherin expression (r = -0.287, P < 0.05). aPKC-iota expression was positively and E-cadherin expression was negatively correlated to the differentiation and invasion of cholangiocarcinoma (P < 0.05). CONCLUSIONS: The expression of aPKC-iota and E-cadherin may reflect the differentiation and invasive potential of cholangiocarcinoma. As a polar regulation-associated protein, aPKC-iota may play a role in the invasion and metastasis of cholangiocarcinoma.

DNA amplification is one of the mechanisms to activate genes that are implicated in neoplastic transformation and gain of chromosome band 3q26 is a common event in squamous cell carcinomas. The aim of the present work was to identify the specific target gene from four candidates (MDS1, PRKCI, ECT2, and PIK3CA) located on 3q26 amplification in esophageal squamous cell carcinomas (ESCCs). To assess the prevalence of copy number gains of putative genes, fluorescence in situ hybridization (FISH) was applied on 108 ESCCs and 9 ESCC cell lines. Our data showed that MDS1 and PRK

Protein kinase Ciota (PKCiota) is an atypical PKC isoform and participates in multiple aspects of the transformed phenotype in human cancer cells. We previously reported that frequent amplification and overexpression of PKCiota were correlated with lymph node metastasis in primary esophageal squamous cell carcinomas (ESCC). In the present study, short interfering RNA-mediated silencing of PKCiota revealed that this enzyme was required for cell migration, invasion, and resistance to anoikis. In vivo experiments showed that PKCiota suppression decreased tumor growth in esophageal cancer xenografts and lung metastases in nude mice. At the molecular level, knockdown of PKCiota in suspended ESCC cells caused a decrease in S-phase kinase-associated protein 2 (SKP2) that had been reported to promote resistance to anoikis via the PI3K/AKT pathway. AKT phosphorylation was abolished after PKCiota suppression, but AKT activation could be refreshed by PKCiota upregulation, suggesting that PKCiota enhanced cell resistance to anoikis via the PKCiota-SKP2-PI3K/AKT pathway. Addition of the proteasome inhibitor MG132 prevented the decrease of SKP2 in PKCiota silenced cells, and polyubiquitin-SKP2 was elevated after PKCiota depletion, showing that PKCiota might regulate the expression of SKP2 through the ubiquitin-proteasome pathway in suspended cells. Furthermore, overexpression of SKP2 in PKCiota-downregulated cells restored cell resistance to anoikis. Most importantly, PKCiota expression significantly correlated with SKP2 in 133 ESCC tissues (P = 0.031). Taken together, our data show that PKCiota promotes tumorigenicity and metastasis of human esophageal cancer and that SKP2 is a candidate downstream effector of PKCiota signaling in ESCC.

BACKGROUND AND OBJECTIVE: Previous studies have indicated that abnormal expression of atypical protein kinase C (aPKC-iota) plays a critical role in occurrence and progression of malignant tumor. This study analyzed the correlation of aPKC-iota with clinicopathology in hepatocarcinoma and Cyclin E and investigated molecular mechanisms of invasion and metastasis of hepatocellular carcinoma. MATERIALS AND METHODS: The expression of the aPKC-iota gene was examined by reverse transcription-polymerase chain reaction in 7 specimens of normal liver tissues and 43 of hepatoma and adjacent tissues. expression of aPKC-iota and Cyclin E protein was detected using immunohistochemistry and Western blot. Finally, we analyzed the correlation of aPKC-iota with clinicopathologic characteristics and invasion of hepatoma. RESULTS: The expression value (0.844 +/- 0.315) of aPKC-iota gene is obviously higher in hepatoma than the value (0.530 +/- 0.217) in adjacent tissues and the value (0.372 +/- 0.130) in normal tissue (P = 0.009). The positive expression rate (58.1%) of aPKC-iota protein in hepatoma is remarkably higher than the rate (23.3%) of adjacent tissues. The expression of aPKC-iota has a positive correlation with the expression of Cyclin E, differentiation degree, and invasion of tumor (P < 0.05). CONCLUSIONS: Differentiation degree and invasion of hepatoma are related to the expression of aPKC-iota, which plays an important role in invasion and metastasis of hepatoma.

OBJECTIVES: Atypical protein kinase C iota (aPKC-iota) and its associated intracellular molecules, E-cadherin and beta-catenin, are important for cell polarization in tumorigenesis and progression. expression of aPKC-iota, P-aPKC-iota (activated aPKC-iota), E-cadherin, and beta-catenin in hepatocellular carcinoma (HCC) was measured, and correlation with clinicopathological characteristics of HCC was analyzed. METHODS: Paraffin-embedded tumor tissue was obtained from patients with HCC after resection without preoperative radiotherapy or chemotherapy. Gene expression was detected by polymerase chain reaction (PCR), and protein expression was detected by immunohistochemistry and Western blot analysis. expressions of aPKC-iota, P-aPKC-iota, E-cadherin, and beta-catenin were analyzed with relation to the clinicopathological data. RESULTS: The gene and protein expression of aPKC-iota are obviously higher in HCC tissues than that in peritumoral tissues and normal tissues by semiquantitative PCR and immunohistochemistry methods. Accumulation of aPKC-iota in HCC cytoplasm and nucleolus inhibited the later formation of belt-like adherens junctions (AJs) and/or tight junctions (TJs) in cell-cell contact. E-cadherin was reduced and accumulation of cytoplasm beta-catenin was increased in HCC. The expression of aPKC-iota was closely related to pathological differentiation, tumor size, invasion, and metastasis of HCC. CONCLUSION: Accumulation of cytoplasm aPKC-iota may reflect pathological differentiation, invasion, and metastasis potential of HCC. In this regard, our study on HCC revealed the potential usefulness of aPKC-iota, E-cadherin, and beta-catenin as a prognostic marker, closely related to pathological differentiation, invasion, metastasis, and prognosis of HCC.

BACKGROUND: The atypical protein kinase C isozyme iota (PKCiota) has been proposed as an oncogene based on its transformation property and amplification identified in Caucasian non-small cell lung cancer (NSCLC) patients. Because the geography difference of some genetic aberrance such as EGFR mutations between Caucasian and Asian NSCLC patients has been identified previously, it is important to know whether the PKCiota amplification also occurs in Asian NSCLC patients. METHODS: The PKCiota gene copy number changes and protein expression in Chinese patients samples were detected by fluorescence in situ hybridization (FISH) and immunohistochemistry (IHC), respectively. Logistic regression was used to assess the association of PKCiota expression with clinicopathological parameters. siRNA-mediated gene silencing was applied to demonstrate the role of PKCiota in promoting cell growth in PKCiota gene amplified and protein overexpressed cancer cells. RESULTS: The result showed that PKCiota gene was amplified in 20.2% (24/119) of the tested primary tumor samples from Chinese NSCLC patients. Interestingly this gene amplification was highly enriched in squamous NSCLC patients (37.1%, 23/62). Further IHC analysis indicated that PKCiota protein was highly expressed (IHC score 2+ and 3+) in 91.6% (109/119) of Chinese NSCLC tumors. Moreover, the PKCiota gene amplification was also correlated with gender, subtype and distant metastasis. Knockdown of PKCiota gene in the PKCiota gene amplified and protein overexpressed cells led to significant growth inhibition. CONCLUSION: Taken together, our data demonstrate that PKCiota is a potential oncogene and therapeutic target in Chinese NSCLC.

Ezrin is a member of the ERM (ezrin, radixin, moesin) protein family and links F-actin to the cell membrane following phosphorylation. Ezrin has been associated with tumor progression and metastasis in several cancers including the pediatric solid tumors, osteosarcoma and rhabdomyosarcoma. In this study, we were surprised to find that ezrin was not constitutively phosphorylated but rather was dynamically regulated during metastatic progression in osteosarcoma. metastatic osteosarcoma cells expressed phosphorylated ERM early after their arrival in the lung, and then late in progression, only at the invasive front of larger metastatic lesions. To pursue mechanisms for this regulation, we found that inhibitors of PKC (protein kinase C) blocked phosphorylation of ezrin, and that ezrin coimmunoprecipitated in cells with PKCalpha, PKCiota and PKCgamma. Furthermore, phosphorylated forms of ezrin and PKC had identical expression patterns at the invasive front of pulmonary metastatic lesions in murine and human patient samples. Finally, we showed that the promigratory effects of PKC were linked to ezrin phosphorylation. These data are the first to suggest a dynamic regulation of ezrin phosphorylation during metastasis and to connect the PKC family members with this regulation.