Metabolic stress induces a Wnt-dependent cancer stem cell-like state transition

Reciprocal interactions between cancer cells and the tumor microenvironment drive multiple clinically significant behaviors including dormancy, invasion, and metastasis as well as therapy resistance. These microenvironment-dependent phenotypes share typical characteristics with cancer stem cells (CSC). However, it is poorly understood how metabolic stress in the confined tumor microenvironment contributes to the emergence and maintenance of CSC-like phenotypes. Here, we demonstrate that chronic metabolic stress (CMS) in a long-term nutrient deprivation induces a Wnt-dependent phenoconversion of non-stem cancer cells toward stem-like state and this is reflected in the transcriptome analysis. Addition of Wnt3a as well as transfection of dominant-negative Tcf4 establishes an obligatory role for the Wnt pathway in the acquisition of CSC-like characteristics in response to metabolic stress. Furthermore, systematic characterization for multiple single cell-derived clones and negative enrichment of CD44+/ESA+ stem-like cancer cells, all of which recapitulate stem-like cancer characteristics, suggest stochastic adaptation rather than selection of pre-existing subclones. Finally, CMS in the tumor microenvironment can drive a CSC-like phenoconversion of non-stem cancer cells through stochastic state transition dependent on the Wnt pathway. These findings contribute to an understanding of the metabolic stress-driven dynamic transition of non-stem cancer cells to a stem-like state in the tumor metabolic microenvironment.

A single-arm, phase II feasibility study of neoadjuvant docetaxel, oxaliplatin, and S-1 (DOS) chemotherapy in potentially resectable gastric or gastroesophageal junction adenocarcinoma

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Background: The aim of this study was to evaluate feasibility and safety of neoadjuvant docetaxel, oxaliplatin, and S-1 (DOS) chemotherapy in patients with potentially resectable adenocarcinoma of stomach or gastroesophageal junction.

Methods: Forty-one patients with clinical stage T3-4N0M0 or T2-4N+M0 determined by CT, endoscopic ultrasonography, and laparoscopy were enrolled between DEC 2008 and MAR 2010. Gastrectomy with D2 lymph node dissection was conducted after 3 cycles of DOS chemotherapy. DOS chemotherapy consists of docetaxel 50 mg/m2 iv (day1), oxaliplatin 100 mg/m2 iv (day1), and S-1 40 mg/m2 po bid (days1-14) at 3 weeks interval. After curative gastrectomy, the patients were given 1 year of adjuvant chemotherapy with S-1 (40 mg/m2 D1-28, every 6 weeks).

Results: All patients finished the planned neoadjuvant chemotherapy. Twenty-three (56%) patients achieved a partial response, and the remaining 18 patients had stable disease by CT scan after 3 cycles of DOS chemotherapy. No disease progression was observed during the neoadjuvant chemotherapy. A median 4.7 weeks (range, 4.0-7.6) after the start of the 3rd cycle of DOS chemotherapy, 39 (95%) patients underwent R0 resection with no pathologic residual disease in 4 (10%) patients. Hematologic toxicities were common including grade 4 neutropenia (32%), grade 3 thrombocytopenia (17%), and febrile neutropenia (10%). However, hematologic toxicities were generally transient and manageable. There were no grade 3 or 4 non-hematologic toxicities with frequency > 5% of patients. With all toxicities taken together, 21 (51%) patients experienced grade 3 or 4 toxicities (except grade 3 neutropenia). There was no treatment-related death, and surgical complications included only mild wound problem in 4 (10%) patients.

Conclusions: In this study, neoadjuvant DOS chemotherapy could induce a sufficient down-staging and R0 resection of locally advanced gastric cancer with mild and manageable toxicities. A phase III randomized trial is planned for evaluating the benefit of neoadjuvant DOS chemotherapy in patients with locally advanced gastric cancer.

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Role of CK1 in GSK3beta-mediated phosphorylation and degradation of snail

The epithelial to mesenchymal transition (EMT) that occurs during embryonic development has begun to attract attention as a potential mechanism for tumor cell metastasis. Snail is a well-known Zn-finger transcription factor that promotes EMT by repressing E-cadherin expression. It is known that Snail is phosphorylated by GSK3beta and degraded by beta-TrCP-mediated ubiquitination. Here we described another protein kinase, CK1, whose phosphorylation of Snail is required for the subsequent GSK3beta phosphorylation. Specific inhibition or depletion of CK1varepsilon inhibits the phosphorylation and degradation of Snail and promotes cell migration, suggesting a central role of CK1varepsilon in the EMT process. Furthermore, our study uncovered distinct roles and steps of Snail phosphorylation by CK1varepsilon and GSK3beta. Taken together, we identified CK1varepsilon as a new component of the Snail-mediated EMT process, providing insight into the mechanism of human cancer metastasis.

Prognostic significance of preoperative serum tumor markers in the patients with curatively resected advanced gastric cancers

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Background: We evaluated the prognostic significance of preoperative tumor markers, carcinoembryonic antigen (CEA), carbohydrate antigen 19–9 (CA19–9), and carbohydrate antigen 72–4 (CA72–4), in the patients with curatively resected advanced gastric cancers (AGC). Methods: Preoperative serum tumor markers were available for 667 patients who had been enrolled in a phase III trial of adjuvant chemotherapy (AMC0201). We compared the relapse free survival (RFS) and overall survival (OS) according to patient's pre-treatment clinical characteristics and serum tumor markers by using log rank test and Cox proportional hazard model. Results: Of total 667 patients, 3 year RFS rate and OS rate were 67.4% and 75.0%, respectively. Postoperative pathologic stage was II in 353 (52.9%), IIIA in 202 (30.3%), IIIB in 61 (9.1%), and IV (M0) in 51 (7.6%). CEA, CA19–9, CA72–4 were elevated pre-operatively in 64 of 665 patients (9.6%), 75 of 664 patients (11.3%), and 121 of 639 patients (18.9%), respectively. After the median follow-up of 38.4 months, 209 patients (31.3%) had recurrence, and 164 patients (24.6%) died. In the univariate analysis, location of tumor, type of surgery, Borrmann type, TNM stage, the elevation of CEA and CA72–4 level were significant prognostic factors for RFS and OS. In the multivariate analysis, serum CA72–4 was independent significant prognostic factor for RFS and OS as well as tumor location, Borrmann type, and stage Conclusions: Pre-operative serum CEA and CA72–4 levels were independent prognostic factors as well as clinical characteristics of pathologic stage, tumor location and Borrmann type in patients with curatively resected AGC.

No significant financial relationships to disclose.

A phase II study of neoadjuvant chemotherapy with docetaxel, capecitabine and cisplatin (DXP) in patients with advanced unresectable or intra-abdominal metastatic gastric cancer

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Background: The prognosis of gastric cancer is dismal once R0 resection is impossible due to local invasion or distant metastasis. Previous studies have suggested the possible efficacy of neoadjuvant chemotherapy for the patients with locally advanced gastric cancer (AGC). The aim of the present study was to evaluate the feasibility, the impact on R0 resection of neoadjuvant chemotherapy in locally advanced, unresectable or intra-abdominal metastatic gastric cancer Methods: Patients with advanced gastric cancer, clinically unresectable because of local invasion or intra-abdominal metastasis in paraaortic lymph nodes and/or peritoneum based on CT scan were entered into this study. Preoperative chemotherapy consisted of docetaxel 60 mg/m2 IV on day 1, cisplatin 60 mg/m2 IV on day 1, and capecitabine 1,875 mg/m2/day PO on days 1 - 14 every 21 days. After 2 cycles of chemotherapy, the tumors were evaluated. Unless disease progression was encountered, surgery was performed after total 3 - 6 cycles of chemotherapy and followed by two cycle of adjuvant therapy with the same regimen if R0 resection was done. Results: Total 49 patients were accrued. Among them, 36 (74%) could undergo surgery, and 31 (63%) had R0 resection. R0 resection was possible in 15 (71%) of 21 patients with initially unresectable T4 lesions and in 12 (70%) of 17 patients with paraaortic lymph node enlargement, while only in 3 (42%) of 7 patients with suspicious peritoneal seeding. After a median follow up of 18.2 months for the surviving patients, median overall survival and progression free survival of total enrolled patients were 19 months (95% C.I, 10.5 - 27.4) and 11.6 months (95% C.I, 9.6 - 13.7), respectively. Among 31 patients who underwent R0 resection, median OS was 33.4 months and median PFS was 18.2 months. Major toxicity was neutropenia and grade 3/4 neutropenia occurred in 77% of patients, but there was only 4% of neutropenic fever and no treatment related mortality. Postoperative morbidities were observed in 4 patients. Conclusions: These data suggested that neoadjuvant DXP chemotherapy could offer a reasonable chance for curative surgery in AGC patients with local invasion or paraaortic lymph node enlargement.

No significant financial relationships to disclose.

Solitary plasmacytoma of the mandible in a renal transplant recipient

A solitary plasmacytoma occurring in the mandible of a 15-year-old Korean male 6 years after renal transplantation is reported. The tumour presented as a hyperplastic gingival overgrowth in the right madibular molar area. Histology and immunohistochemistry revealed plasmacytoma and monoclonality of the kappa chain and IgG. In situ hybridization for Epstein-Barr virus encoded RNA (EBER) showed positive signals in the tumour cells. The tumour regressed after reducing the immunosuppressive agents with concurrent radiotherapy. The patient remains in a stable condition with normal renal functions after 7 years without recurrence. This case confirms that Epstein-Barr virus associated B-lymphoproliferative disorders are still a major complication of immunosuppression.

Malignant lymphoma of the maxillary sinus manifesting as a persistent toothache

Many teeth have been mistakenly extracted or endodontically treated because of an incorrect diagnosis of orofacial pain, including toothache. A case of persistent toothache originating from a malignant lymphoma of the left maxillary sinus is presented. Root canal therapy and extraction of the upper left quadrant teeth from the canine to the second molar did not resolve the chief complaint. The patient was referred to a neurologist and received a diagnosis of a malignant lymphoma, a rare lesion of the maxillary sinus. This case stresses the importance of considering malignant neoplasm of the maxillary sinus as a potential etiologic factor in the differential diagnosis of orofacial pain.

Evaluation of premalignant potential in oral lichen planus using interphase cytogenetics

This study attempted to evaluate whether oral lichen planus (OLP) has the potential to progress to oral squamous cell carcinoma (OSCC) by comparing the degree of genetic instability between clinically-curable OLP and lesions that progressed to OSCC. Fifteen cases of steroid-responsive OLP and two cases of lichenoid dysplasia (LD) that progressed to OSCC were used for this study. Chromosome in situ hybridization (CISH) was performed for chromosomes 9 and 17. The fraction of polysomic and monosomic cells for chromosome 9 increased in mucosal epithelium compared to those of lymphocytes in OLP. This difference was statistically significant (P=0.0017, 0.0054, respectively). Two LD patients showed 15.38% and 22.58% of PI for chromosome 9. In OSCC that developed from LD, the fraction of monosomic cells for chromosome 9 increased by more than 70%. We concluded that LD should be treated as a high-risk premalignant lesion and strongly suggest that the monosomy of chromosome 9 may have a critical role in progress to malignancy from LD.

Odontogenic ghost cell carcinoma: a case report with reference to the relation between apoptosis and ghost cells

The neoplastic variant of calcifying odontogenic cyst has various designations, and its malignant counterpart has been reported as aggressive epithelial odontogenic ghost cell tumor or odontogenic ghost cell carcinoma. We present a case of odontogenic ghost cell carcinoma with reference to the relation between the ghost cells and apoptosis. A 33-year-old man complained of a mandibular mass. The mass occupied the entire right side of the mandible with destruction of both buccal and lingual bone. The mass also infiltrated into submandibular and sublingual spaces. Histologically, the mass was composed of a solid proliferation of hyperchromatic and pleomorphic epithelial cells with abnormal mitoses. Islands of ghost cells were frequently admixed with nucleated cells, and there were foci of ameloblastic differentiation. Immunohistochemical stains for cytokeratins, involucrin, and apoptosis-related proteins such as Bcl-2, Bcl-X(L), and Bax were done. Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling (TUNEL) assay was also performed. The nucleated cells adjacent to the ghost cells expressed cytokeratins and involucrin, but the ghost cells had no reaction. Bcl-2 was negative. Both Bcl-X(L) and Bax were demonstrated in the nucleated cells adjacent to the ghost cells. The ghost cells exhibited Bax protein. Some nucleated cells adjacent to the ghost cells were positive with TUNEL assay. The above results indicate that ghost cells undergo abnormal terminal differentiation as an apoptotic process.

Pharmacological characterization of (10bS)-1,2,3,5,6,10b-hexahydropyrrolo[2,1-a]isoquinoline oxalate (YSL-3S) as a new alpha2-adrenoceptor antagonist

Alpha2-adrenoceptor antagonists, which can enhance synaptic norepinephrine levels by blocking feedback inhibition processes, are potentially useful in the treatment of disease states such as depression, memory impairment, impotence and sexual dysfunction. (10bS)-1,2,3,5,6,10b-Hexahydropyrrolo[2,1-a]isoquinoline oxalate (YSL-3S) was evaluated in several in vitro biological tests to establish its pharmacological profile of activities as an alpha2-adrenoceptor antagonist. Saturation binding assay revealed that [3H]rauwolscine bound to the alpha2-adrenoceptors with a Kd value of 6.3+/-0.5 nM and a Bmax value of 251+/-39 fmol/mg protein in rat cortical synaptic membranes. Competitive binding assay showed that YSL-3S inhibited the binding of [3H]rauwolscine (1 nM) in a concentration-dependent manner with a Ki value of 98.2+/-12.1 nM while it did not inhibit the binding of [3H]cytisine (1.25 nM) to neuronal nicotinic cholinergic receptors. The Ki values of yohimbine, clonidine and norepinephrine for [3H]rauwolscine binding were 15.8+/-1.0, 40.1+/-5.9 and 40.0+/-11.5 nM, respectively. In addition, the binding affinity of YSL-3S for alpha2-adrenoceptors was higher than that of its antipode and the racemic mixture. The functional activity of YSL-3S at the presynaptic alpha2-adrenoceptors was assessed using the prostatic portion of the rat vas deferens. Clonidine inhibited field-stimulated contractions of the vas deference in a dose-dependent manner. The presence of YSL-3S or yohimbine caused a parallel, rightward the dose-response curve of clonidine in a dose-dependent manner, indicating an antagonistic action at the presynaptic alpha2-adrenoceptors. The pA2 values of yohimbine and YSL-3S were 7.66+/-0.13 and 6.64+/-0.18, respectively. The results indicate that YSL-3S acts as a competitive antagonist at presynaptic alpha2-adrenoceptors with a potency approximately ten times lower than yohimbine, but is devoid of binding affinity for neuronal nicotinic cholinergic receptors.

Anti-promotion effect of chlorophyllin in DMBA-TPA-induced mouse skin carcinogenesis

This study aimed to elucidate the inhibitory effects of chlorophyllin (CHL) at different promotion stages in a DMBA-TPA-induced mouse skin carcinogenesis model. TPA promotion was undertaken for 6, 18 and 24 weeks, respectively. Proliferating activity was observed immunohistochemically and the ornithine decarboxylase (ODC) mRNA level was analyzed by reverse transcriptase-polymerase chain reaction. Messenger RNAs for c-fos, c-jun and jun-B were also observed. CHL treatment clearly reduced proliferating activity and the level of ODC mRNA at the 18-week-promotion stage. When promoted for 24 weeks, CHL was not effective in reducing proliferating activity and ODC mRNA expression. These results indicate that the promotion stage of each target tissue should be considered in a chemopreventive program.

Low convulsive activity of a new carbapenem antibiotic, DK-35C, as compared with existing congeners

Since carbapenems and cephalosporins have been suggested to induce convulsive side effects through an inhibitory action on the central gamma-aminobutyric acid (GABA)-mediated inhibitory transmission, the present study evaluated the convulsive activity of a new carbapenem antibiotic (1R,5S,6S)-6[(R)-1-hydroxyethyl]-2-[(3S,5S)-5(S-methyl-4thiomorpholin ylcarbonyl)pyrrolidin-3-thio]-l-methylcarbapen-2-em-3- carboxylic acid (DK-35C) in in vitro and in vivo experiments, in comparison with cefazolin, imipenem and meropenem. In in vitro experiments, their abilities to inhibit [3H]muscimol (5 nM) binding to GABA(A) receptors were measured using crude synaptic membranes prepared from the rat cerebral cortex. The concentrations (mM) of the antibiotics which inhibit 50% of the specific binding, were 0.6 for imipenem, 1.8 for cefazolin, 15.4 for DK-35C and 27.6 for meropenem. In in vivo experiments, intracerebroventricular (i.c.v.) injections of cefazolin, imipenem and DK-35C induced convulsions in a dose-dependent manner in rats. The doses (nmol/rat) of the antibiotics which induce convulsions in 50% of rats, were 57 for imipenem, 96 for cefazolin, 377 for DK-35C and >3000 for meropenem. In the mouse pentylenetetrazole (PTZ) convulsive model, intravenous pretreatment with cefazolin (800 mg/kg) or imipenem (200 mg/kg) shifted the dose-response curve of PTZ (i.p.) to the left, indicating enhancement of the convulsive activity of PTZ. However, pretreatment with cefazolin, meropenem or DK-35C at a dose of 400 mg/kg did not produce any marked effects on the convulsive activity of PTZ compared with the saline vehicle-pretreated control. The results clearly demonstrate a good correlation between in vitro GABA(A) receptor binding assay and in vivo i.c.v. convulsive model using rats, and suggest that DK-35C may possess a relatively weak convulsive activity mediated through an interaction with GABA(A) receptors.

Inhibitory effects of chlorophyllin on 7,12-dimethylbenz[a]anthracene-induced bacterial mutagenesis and mouse skin carcinogenesis

Chlorophyllin (CHL), a water-soluble derivative of chlorophyll, has been used for the treatment of several abnormal human conditions without apparent toxicity. Recent studies have revealed that CHL has the excellent chemopreventive potential. In the present investigation, we have found the inhibitory activities of CHL against 7,12-dimethylbenz[a]anthracene (DMBA)-induced mutagenesis in Salmonella typhimurium TA100 and also on DMBA-initiated and 12-O-tetradecanoyl-phorbol-13-acetate (TPA)-promoted mouse skin tumor formation. The incidence and the multiplicity of skin tumors were not significantly decreased in mice by a single topical application of CHL prior to the DMBA treatment, but there was a marked suppression of papillomagenesis in mice treated with CHL during the promotional stage. Furthermore, the formation of DMBA-induced papillomagenesis was reduced in all mice that had received CHL for 6 weeks following treatment with TPA for 6, 18 and 24 weeks. These results indicate that CHL can inhibit both tumor promotion and the progression of papillomagenesis in the two-stage mouse skin carcinogenesis induced by DMBA and TPA.

Binding affinities of 3-(3-phenylisoxazol-5-yl)methylidene-1-azabicycles to acetylcholine receptors

A series of 3-(3-phenylisoxazol-5-yl)methylidene-1-azabicycles synthesized showed different binding characteristics to acetylcholine receptors depending on the substituents on the phenyl ring. Small polar substituents gave preferential binding affinity to nicotinic receptors, and large hydrophobic substituents to muscarinic receptors.

Intermittent parathyroid hormone treatment can promote linear growth in the ovariectomized growing rat

To compare the effect of intermittent parathyroid hormone (PTH) treatment with that of estrogen treatment on epiphyseal growth in ovariectomized rats, 46 Sprague-Dawley female rats aged 9-10 weeks (about 200-220 g) were either ovariectomized or sham operated. From 6 weeks after ovariectomy (ovx), rats were daily injected with subcutaneous human recombinant PTH (1-84)-dosed 30 micrograms/kg (the low dose PTH-treated group) or 300 micrograms/kg (the high dose PTH-treated group), 17 beta-estradiol (the 17 beta-estradiol-treated group, 30 micrograms/kg) or vehicle (the ovx-alone group), 5 times a week for 4 weeks. The decalcified sections of the distal femoral epiphyseal plate were analyzed on light microscopy after H&E stain, and the lengths of the zones of proliferation, maturing and hypertrophic chondrocytes were measured. The length of the growth plate, the zone of proliferation and the zone of hypertrophic chondrocyte in the ovx-alone group were significantly shorter than those of the sham-operated group. The treatment of 17 beta-estradiol speeded up the differentiation of cells from proliferating chondrocytes to maturing and hypertrophic chondrocytes even though the length of the growth plate was comparable to that of the sham-operated group. Both low and high dose PTH treatments increased the length of the growth plate, and those lengths were comparable to that of the sham-operated group. The fractions of proliferating, maturing and hypertrophic zone in the low dose PTH-treated group were also comparable to those of the sham-operated group. However, high dose PTH treatment slowed down the differentiation of cells from proliferating chondrocytes to maturing and hypertrophic chondrocytes to a greater extent, and therefore the fraction of proliferating chondrocytes of the high dose PTH-treated group was larger than that of the low dose PTH-treated group (73.8 +/- 1.8 Vs 63.3 +/- 1.3%, p < 0.005). From these results, we showed that intermittent PTH treatment could promote linear growth in the ovariectomized growing rat. We propose that PTH may be an alternative drug candidate for promoting linear growth of long bones without the risk for early closure of the growth plate.

Lack of tumor promoting activity of capsaicin, a principal pungent ingredient of red pepper, in mouse skin carcinogenesis

Capsaicin (trans-8-methyl-N-vanillyl-6-nonenamide) is the major pungent principle of hot peppers of the genus Capsicum. There have been numerous investigations to evaluate the effects of capsaicin on experimental carcinogenesis and mutagenesis, but the results are discordant. In the present study, we have assessed the tumor promoting potential of capsaicin using a two stage mouse skin carcinogenesis model. Repeated applications of capsaicin (10 mumol) onto the shaven backs of female ICR mice following a single-initiation dose of 7,12-dimethylbenz[alpha]anthracene did not cause any significant increase in papilloma formation and abnormal hyperplastic or inflammatory skin lesions, compared with the solvent control. Furthermore, the topical application of capsaicin did not induce the epidermal ornithine decarboxylase activity, suggesting that it lacks tumor-promotional activity. On the contrary, the compound ameliorated the mouse skin carcinogenesis when given simultaneously with the tumor promoter, 12-O-tetradecanoylphorbol-13-acetate.

Expression of p21WAF1/CIP1 is unrelated to p53 tumour suppressor gene status in oral squamous cell carcinomas

The p53 tumour suppressor gene is frequently mutated in oral squamous cell carcinomas. However, the downstream mechanism of p53 during oral carcinogenesis is not fully understood. The cyclin-dependent kinase inhibitor p21WAF1/CIP1 (p21), which can be induced by wild-type p53, functions as a downstream mediator of the antiproliferative and apoptosis-inducing actions of wild-type p53. To learn more about the roles of the p53 gene and its downstream mechanism, we evaluated p53 gene mutation and immunohistochemical expression of p53 and p21 in 20 cases of oral squamous cell carcinoma. p53 gene mutations were observed in 7 cases (35%). Overexpression of p53 was found in 4 of 13 cases with wild-type p53, and in 6 of 7 cases with p53 mutations. p21 expression was detected in 15 of 20 cases (75%). The expression of p21 correlated neither with mutated p53 mutation nor with p53 protein overexpression. p21 was expressed even in carcinomas in which molecular analysis revealed a nonsense mutation. In normal oral mucosa, p21 expression was limited in the differentiating spinous cell layer. However, dysplastic or hyperplastic epithelium adjacent to the tumour demonstrated the increased expression of p21 even in the proliferating basal cell layer. These molecular and immunohistochemical data did not show any correlation with various clinico-pathologic parameters. These results suggest that p53 gene mutations and altered expression of p21 are commonly involved in oral carcinogenesis, but do not correlate with each other or with the clinico-pathologic parameters. They also suggest that p21 expression in oral squamous cell carcinomas may be induced by a p53-independent pathway.

Immunohistochemical study on proliferating cell nuclear antigen expression in ameloblastomas

The aim of this study is to evaluate the proliferating activity of ameloblastomas and its correlation to the biological behaviour according to each histological type. 38 cases of solid and unicystic ameloblastomas were reviewed including 1 case of ameloblastic carcinoma and 1 recurrent case. An anti-PCNA antibody, PC10(Dako), was applied for the detection of proliferating cell nuclear antigen (PCNA) in paraffin embedded tissue sections. Also 20 cases of dentigerous cysts were reviewed. In conclusion, we observed that there was no difference between the proliferating activities of the different histological types of solid ameloblastomas. Because 1 case of ameloblastic carcinoma and one recurrent case revealed remarkably high PCNA reactivity, we believe that PCNA would be useful in showing the differentiation between benign and malignant ameloblastomas. In unicystic ameloblastomas, plexiform intraluminal growth was considered to be an important feature in tumorous transformation of cystic epithelium.