Pepsin Promotes Activation of Epidermal Growth Factor Receptor and Downstream Oncogenic Pathways, at Slightly Acidic and Neutral pH, in Exposed Hypopharyngeal Cells.

Pepsin refluxate is considered a risk factor for laryngopharyngeal carcinogenesis. Non-acidic pepsin was previously linked to an inflammatory and tumorigenic effect on laryngopharyngeal cells in vitro. Yet there is no clear evidence of the pepsin-effect on a specific oncogenic pathway and the importance of pH in this process. We hypothesized that less acidic pepsin triggers the activation of a specific oncogenic factor and related-signalling pathway. To explore the pepsin-effect in vitro, we performed intermittent exposure of 15 min, once per day, for a 5-day period, of human hypopharyngeal primary cells (HCs) to pepsin (1 mg/mL), at a weakly acidic pH of 5.0, a slightly acidic pH of 6.0, and a neutral pH of 7.0. We have documented that the extracellular environment at pH 6.0, and particularly pH 7.0, vs. pH 5.0, promotes the pepsin-effect on HCs, causing increased internalized pepsin and cell viability, a pronounced activation of EGFR accompanied by NF-κB and STAT3 activation, and a significant upregulation of EGFR, AKT1, mTOR, IL1ß, TNF-α, RELA(p65), BCL-2, IL6 and STAT3. We herein provide new evidence of the pepsin-effect on oncogenic EGFR activation and its related-signaling pathway at neutral and slightly acidic pH in HCs, opening a window to further explore the prevention and therapeutic approach of laryngopharyngeal reflux disease.

H+/K+ATPase Expression in the Larynx of Laryngopharyngeal Reflux and Laryngeal Cancer Patients.

OBJECTIVES: The gastric H+/K+ ATPase proton pump has previously been shown to be expressed in the human larynx, however its contribution to laryngopharyngeal reflux (LPR) signs, symptoms and associated diseases such as laryngeal cancer is unknown. Proton pump expression in the larynx of patients with LPR and laryngeal cancer was investigated herein. A human hypopharyngeal cell line expressing the proton pump was generated to investigate its effects. STUDY DESIGN: In-vitro translational. METHODS: Laryngeal biopsies were obtained from three LPR and eight LSCC patients. ATP4A, ATP4B and HRPT1 were assayed via qPCR. Human hypopharyngeal FaDu cell lines stably expressing proton pump were created using lentiviral transduction and examined via transmission electron microscopy and qPCR for genes associated with inflammation or laryngeal cancer. RESULTS: Expression of ATP4A and ATP4B was detected in 3/3 LPR, 4/8 LSCC-tumor and 3/8 LSCC-adjacent specimens. Expression of ATP4A and ATP4B in FaDu elicited mitochondrial damage and expression of IL1B, PTGS2, and TNFA (P < .0001); expression of ATP4B alone did not. CONCLUSIONS: Gastric proton pump subunits are expressed in the larynx of LPR and LSCC patients. Mitochondrial damage and changes in gene expression observed in cells expressing the full proton pump, absent in those expressing a single subunit, suggest that acid secretion by functional proton pumps expressed in upper airway mucosa may elicit local cell and molecular changes associated with inflammation and cancer. LEVEL OF EVIDENCE: NA Laryngoscope, 131:130-135, 2021.

Assessment of cancer stem cell marker expression in primary head and neck squamous cell carcinoma shows prognostic value for aldehyde dehydrogenase (ALDH1A1).

Cancer stem cells (CSCs) play a key role in carcinogenesis and progression of head and neck squamous cell carcinomas (HNSCC). The most common markers indicating for CSCs are: CD44, CD24, CD133, ALDH1A1. Our objective was to evaluate the prognostic potential of CSC markers in HNSCC. The study included 49 patients treated for primary HNSCC, 11 patients with upper respiratory tract epithelial dysplasia and 12 subjects with the normal pharyngeal mucosa as a control group. The frequency and expression levels of the four CSC markers were assessed by immunohistochemistry. Univariate and multivariate analyses were used to correlate CSC expression levels with tumor stage, lymph node metastases or overall survival (OS). CD44, CD24, CD133, ALDH1A1 were widely expressed in tumors, whereas CD44 was found to be higher in cancer tissue (P = 0.001). ALDH1A1 expression levels were found to be significantly higher in T3-T4 tumors vs. T1-T2 tumors (P = 0.05). Lymph node metastases had significantly higher expression levels of CD24 (P = 0.01) and CD133 (P < 0.05) than primary tumors. Multifactorial analysis revealed that overall survival (OS) for patients with ALDH1A1 negative tumors was 5.25 times higher than for patients with ALDH1A1 positive (ALDH1A1+) tumors (P = 0.01). On univariate and multivariate analysis, only ALDH1A1 positivity had a significant effect on OS of HNSCC patients (HR = 2.47 for P = 0.02). Immunohistochemistry-based assessments of CSC marker expression in HNSCC has significant predictive implications for patients with HNSCC. The frequency of CSCs in the tumor, specifically of ALDH1A1+ cells correlated with five-year OS in these patients.

Biliary tumorigenic effect on hypopharyngeal cells is significantly enhanced by pH reduction.

Biliary reflux has been considered a potential risk factor in upper aerodigestive tract malignancies. It is not yet clearly known how pH affects the bile-induced activation of NF-κB and its related oncogenic pathway previously linked to hypopharyngeal carcinogenesis. In this study, repetitive applications of conjugated primary bile acids with unconjugated secondary bile acid, deoxycholic acid (DCA), on human hypopharyngeal primary cells reveal that strongly acidic pH (4.0) optimally enhances the tumorigenic effect of bile, by inducing activation of NF-κB, STAT3 nuclear translocation, bcl-2 overexpression and significant overexpression of the oncogenic mRNA phenotype, compared to weakly acidic pH (5.5) or neutral pH (7.0). As the pH becomes less acidic the partially activated primary bile acids and activated DCA begin to exert their influence; however, with significantly less intensity compared to bile acids at strongly acidic pH. Our findings suggest that biliary tumorigenic effect is strongly pH dependent. Controlling pH during reflux events may be therapeutically effective in reducing the potential risk of bile-induced hypopharyngeal cancer.

Optimized Generation of Primary Human Epithelial Cells from Larynx and Hypopharynx: A Site-Specific Epithelial Model for Reflux Research.

Laryngopharyngeal reflux (LPR) induces a differential damage effect on several anatomic sites within the larynx and hypopharynx; therefore, an in vitro model is needed for each anatomic site. This study aimed to establish a primary culture method for human laryngeal and hypopharyngeal epithelial cells derived from multiple anatomic sites. Surgical mucosa specimens were treated with a two-step enzymatic strategy to establish a primary culture. Of the 46 samples, primary cultivation was achieved successfully with 36 samples, and the positive ratio was 78.3%. In addition, flow cytometry revealed that these primary cells were epithelial cells with a purity of 94.9%. The proliferative ability was confirmed by positive staining for Ki-67. Laryngeal and hypopharyngeal epithelial cells from multiple sites exhibited similar epithelial morphology and positive cytokeratin expression. These cells can be cultured to passage 4. In summary, we successfully established the in vitro epithelial model of larynx and hypopharynx subsites, which may potentially be used as a platform for reflux research, especially for site-specific damage effect.

Curcumin prevents the bile reflux-induced NF-κB-related mRNA oncogenic phenotype, in human hypopharyngeal cells.

The presence of bile is not an uncommon finding in acidic oesophageal and extra-oesophageal refluxate, possibly affecting the hypopharyngeal mucosa and leading to neoplastic events. We recently demonstrated that acidic bile (pH ≤ 4.0) can induce NF-κB activation and oncogenic mRNA phenotype in normal hypopharyngeal cells and generate premalignant changes in treated hypopharyngeal mucosa. We hypothesize that curcumin, a dietary inhibitor of NF-κB, may effectively inhibit the acidic bile-induced cancer-related mRNA phenotype, in treated human hypopharyngeal primary cells (HHPC), supporting its potential preventive use in vivo. Luciferase assay, immunofluorescence, Western blot, qPCR and PCR microarray analysis were used to explore the effect of curcumin in HHPC exposed to bile (400 µmol/L) at acidic and neutral pH. Curcumin successfully inhibited the acidic bile-induced NF-κB signalling pathway (25% of analysed genes), and overexpression of NF-κB transcriptional factors, c-REL, RELA(p65), anti-apoptotic bcl-2, oncogenic TNF-α, EGFR, STAT3, WNT5A, ΔNp63 and cancer-related IL-6. Curcumin effectively reduced bile-induced bcl-2 overexpression at both acidic and neutral pH. Our novel findings suggest that, similar to pharmacologic NF-κB inhibitor, BAY 11-7082, curcumin can suppress acidic bile-induced oncogenic mRNA phenotype in hypopharyngeal cells, encouraging its future in vivo pre-clinical and clinical explorations in prevention of bile reflux-related pre-neoplastic events mediated by NF-κB.

NF-κB inhibition reverses acidic bile-induced miR-21, miR-155, miR-192, miR-34a, miR-375 and miR-451a deregulations in human hypopharyngeal cells.

We previously demonstrated that acidic bile activates NF-κB, deregulating the expression of oncogenic miRNA markers, in pre-malignant murine laryngopharyngeal mucosa. Here, we hypothesize that the in vitro exposure of human hypopharyngeal cells to acidic bile deregulates cancer-related miRNA markers that can be reversed by BAY 11-7082, a pharmacologic NF-κB inhibitor. We repetitively exposed normal human hypopharyngeal primary cells and human hypopharyngeal keratinocytes to bile fluid (400 µmol/L), at pH 4.0 and 7.0, with/without BAY 11-7082 (20 µmol/L). We centred our study on the transcriptional activation of oncogenic miR-21, miR-155, miR-192, miR-34a, miR-375, miR-451a and NF-κB-related genes, previously linked to acidic bile-induced pre-neoplastic events. Our novel findings in vitro are consistent with our hypothesis demonstrating that BAY 11-7082 significantly reverses the acidic bile-induced oncogenic miRNA phenotype, in normal hypopharyngeal cells. BAY 11-7082 strongly inhibits the acidic bile-induced up-regulation of miR-192 and down-regulation of miR-451a and significantly decreases the miR-21/375 ratios, previously related to poor prognosis in hypopharyngeal cancer. This is the first in vitro report that NF-κB inhibition reverses acidic bile-induced miR-21, miR-155, miR-192, miR-34a, miR-375 and miR-451a deregulations in normal human hypopharyngeal cells, suggesting that acidic bile-induced events are directly or indirectly dependent on NF-κB signalling.

The In Vitro Effect of Acidic-Pepsin on Nuclear Factor KappaB Activation and Its Related Oncogenic Effect on Normal Human Hypopharyngeal Cells.

BACKGROUND: Extra-esophageal carcinogenesis has been widely discussed in relation to the chronic effects of laryngopharyngeal reflux and most prominently with pepsin historically central to this discussion. With refluxate known to include gastric (pepsin) and duodenal (bile) fluids, we recently demonstrated the mechanistic role of NF-κB in mediating the preneoplastic effects of acidic-bile. However, the role of pepsin in promoting hypopharyngeal premalignant events remains historically unclear. Here, we investigate the in vitro effect of acidic-pepsin on the NF-κB oncogenic pathway to better define its potential role in hypopharyngeal neoplasia. METHODS: Human hypopharyngeal primary cells (HHPC) and keratinocytes (HHK) were repetitively exposed to physiologic pepsin concentrations (0.1 mg/ml) at pH 4.0, 5.0 and 7.0. Cellular localization of phospho-NF-κB and bcl-2 was determined using immunofluorescence and western blotting. NF-κB transcriptional activity was tested by luc reporter and qPCR. Analysis of DNA content of pepsin treated HHK and HHPC was performed using Fluorescence-activated-cell sorting assay. To explore a possible dose related effect, pepsin concentration was reduced from 0.1 to 0.05 and 0.01 mg/ml. RESULTS: At physiologic concentration, acidic-pepsin (0.1 mg/ml at pH 4.0) is lethal to most normal hypopharyngeal cells. However, in surviving cells, no NF-κB transcriptional activity is noted. Acidic-pepsin fails to activate the NF-κB or bcl-2, TNF-α, EGFR, STAT3, and wnt5α but increases the Tp53 mRNAs, in both HHPC and HHK. Weakly acidic-pepsin (pH 5.0) and neutral-pepsin (pH 7.0) induce mild activation of NF-κB with increase in TNF-α mRNAs, without oncogenic transcriptional activity. Lower concentrations of pepsin at varying pH do not produce NF-κB activity or transcriptional activation of the analyzed genes. CONCLUSION: Our findings in vitro do not support the role of acidic-pepsin in NF-κB related hypopharyngeal carcinogenesis.

Secretory cells in honeybee hypopharyngeal gland: polarized organization and age-dependent dynamics of plasma membrane.

The honeybee hypopharyngeal gland consists in numerous units, each comprising a secretory cell and a canal cell. The secretory cell discharges its products into a convoluted tubular membrane system, the canaliculus, which is surrounded at regular intervals by rings of actin filaments. Using probes for various membrane components, we analyze the organization of the secretory cells relative to the apicobasal configuration of epithelial cells. The canaliculus was defined by labeling with an antibody against phosphorylated ezrin/radixin/moesin (pERM), a marker protein for the apical membrane domain of epithelial cells. Anti-phosphotyrosine visualizes the canalicular system, possibly by staining the microvillar tips. The open end of the canaliculus leads to a region in which the secretory cell is attached to the canal cell by adherens and septate junctions. The remaining plasma membrane stains for Na,K-ATPase and spectrin and represents the basolateral domain. We also used fluorophore-tagged phalloidin, anti-phosphotyrosine and anti-pERM as probes for the canaliculus in order to describe fine-structural changes in the organization of the canalicular system during the adult life cycle. These probes in conjunction with fluorescence microscopy allow the fast and detailed three-dimensional analysis of the canalicular membrane system and its structural changes in a developmental mode or in response to environmental factors.

Intrinsic neuroendocrine cells in the outer wall of the human pyriform recess.

The extrinsic neural supply of the hypopharynx is well established. However, little is known about the intrinsic neurons and neuroendocrine cells (NECs) of the human hypopharynx that are under the influence of the extrinsic nerves. We aimed to identify and characterize such cell populations within the outer wall of the pyriform recess. We applied antibodies for neuron-specific enolase (NSE), calretinin (CR) and neurofilaments (NF) to autopsy samples from four donor cadavers. Within the lamina propria and the muscle layer of the pyriform recess outer wall, usually in perivascular areas, we found NSE-, CR- and NF-positive cells, mostly apolar, that were considered on a histological and immunohistochemical basis to be NECs. Although these cells have not, to our knowledge, been described previously in this anatomical location, their presence within the hypopharynx wall may explain the appearance of rare forms of local primary neuroendocrine carcinomas.

Chronic pepsin exposure promotes anchorage-independent growth and migration of a hypopharyngeal squamous cell line.

OUTCOME OBJECTIVES: (1) Investigate the role of reflux, specifically pepsin, in laryngopharyngeal carcinogenesis. (2) Evaluate effects of chronic pepsin exposure on cell migration, apoptosis, and colony-forming ability in hypopharyngeal cells. STUDY DESIGN: Translation research. SETTING: Academic research laboratory. METHODS: Human hypopharyngeal squamous carcinoma FaDu cells were chronically exposed to nonacidic pepsin (exposed for 24 hours, 4 times over 2 weeks at the following concentrations: 0.01 mg/mL, 0.1 mg/mL, or 1 mg/mL). Precise wounds were created in confluent cell plates, and rates of cell migration into wounds were quantified. Separately, cell viability of chronic pepsin-exposed FaDu cells acutely treated with paclitaxel was measured. Finally, a clonogenic assay was performed on these cells to measure effects of chronic pepsin exposure on colony-forming ability. RESULTS: An increased rate of relative wound density was observed in chronic pepsin-treated (0.01 mg/mL, 0.1 mg/mL) cells compared with control (P < .001), suggesting greater rates of cell migration. Pepsin-treated (0.1 mg/mL) cells demonstrated on average greater cell viability compared with control after exposure to paclitaxel, suggesting possible apoptotic resistance; however, this was not statistically significant. Chronic pepsin exposure (0.1 mg/mL, 1 mg/mL) was associated with a dose-dependent increase in colony-forming ability relative to control (P < .001). CONCLUSION: Hypopharyngeal squamous cell line chronically exposed to pepsin demonstrated increased cell migration and colony-forming ability relative to control cells. These experiments indicate that chronic pepsin exposure acts as a promoter of tumorigenesis and metastasis of airway epithelium, suggesting a role for pepsin in laryngopharyngeal carcinogenesis attributed to gastric reflux.

Aging and its modulation in a long-lived worker caste of the honey bee.

Highly social animals provide alternative aging models in which vastly different lifespan patterns are flexible, and linked to social caste. Research in these species aims to reveal how environment, including social cues, can shape the transition between short-lived and extremely long-lived phenotypes with negligible senescence. Among honey bee workers, short to intermediate lifespans are typical for summer castes, while the winter caste can live up to 10 times longer. For summer castes, experimental interventions could predictably accelerate, slow or revert functional senescence. In contrast, little is known about the partic ular conditions under which periods of negligible senescence in winter castes can be disrupted or sustained. We asked how manipulation of social environment in colonies with long-lived winter bees might alter the pace of functional senescence, measured as learning performance, as well as of cellular senescence, measured as lipofuscin accumulation. We show that behavioral senescence becomes rapidly detectable when the winter state is disrupted, and changes in social task behaviors and social environment (brood) are induced. Likewise, we found that cellular senescence was induced by such social intervention. However, cellular senescence showed marked regional differences, suggesting that particular brain regions age slower than others. Finally, by preventing post-winter colonies from brood rearing, behavioral senescence became undetectable, even after transition to the usually short-lived phenotypes had occurred. We envision that social regulation of negligible functional senescence and highly dynamic accumulation of a universal symptom of cellular aging (lipofuscin) offers rewarding perspectives to target proximate mechanisms of slowed aging.

Surface modification of polyurethane towards promoting the ex vivo cytocompatibility and in vivo biocompatibility for hypopharyngeal tissue engineering.

Polymeric substrates with good biocompatibility have been widely employed to create a living construct with the complexities of tissue histology and function in the field of tissue engineering. In this study, poly(ester-urethane) (58213, NAT022) was used to be substrate due to its good physical and chemical properties. Proteins like gelatin or silk fibroin were covalently bonded on its surface using method of diamine aminolysis and glutaraldehyde crosslinking, which had been setup in our group in order to improve poly(ester-urethane)'s hydrophilicity and biocompatibility. The modification was proved by the measurements of static and dynamic contact angles and fluorescence detection. The biological properties were evaluated as in vitro cell culture and in vivo transplantation via cell number counting, morphology observation, immunohistochemistry analysis, etc. The results showed that gelatin or silk fibroin grafted membrane displayed good cytocompatibility, i.e. good proliferation and differentiation of human hypopharynx fibroblast and skeletal muscle cell though the control poly(ester-urethane) indicated low toxicity to cells and good biocompatibility, which was also verified in in vivo experiment. After poly(ester-urethane)-silk fibroin was implanted subcutaneously in rat back, it exhibited a better compatibility to peripheral tissue and faster biodegradation than the control poly(ester-urethane) did. This information supplied us valuable knowledge for poly(ester-urethane) to be used as matrix in situ hypopharynx regeneration study.

Engineered hypopharynx from coculture of epithelial cells and fibroblasts using poly(ester urethane) as substratum.

Porous polymeric scaffolds have been much investigated and applied in the field of tissue engineering research. Poly(ester urethane) (PEU) scaffolds, comprising pores of 1-20 µ m in diameter on one surface and ≥ 200 µ m on the opposite surface and in bulk, were fabricated using phase separation method for hypopharyngeal tissue engineering. The scaffolds were grafted with silk fibroin (SF) generated from natural silkworm cocoon to enhance the scaffold's hydrophilicity and further improve cytocompatibility to both primary epithelial cells (ECs) and fibroblasts of human hypopharynx tissue. Coculture of ECs and fibroblasts was conducted on the SF-grafted PEU scaffold (PEU-SF) to evaluate its in vitro cytocompatibility. After co-culture for 14 days, ECs were lined on the scaffold surface while fibroblasts were distributed in scaffold bulk. The results of in vivo investigation showed that PEU porous scaffold possessed good biocompatibility after it was grafted by silk fibroin. SF grafting improved the cell/tissue infiltration into scaffold bulk. Thus, PEU-SF porous scaffold is expected to be a good candidate to support the hypopharynx regeneration.

Pepsin promotes proliferation of laryngeal and pharyngeal epithelial cells.

OBJECTIVE/HYPOTHESIS: Laryngopharyngeal reflux (LPR) is thought to be a significant risk factor for laryngeal squamous cell carcinoma (SCC), but causality has never been proven. It is accepted that chronic reflux into the esophagus can induce metaplastic changes in esophageal mucosa with subsequent increased risk of esophageal adenocarcinoma, but no similar associations have been established for LPR and laryngopharyngeal SCC. The objective of this study was to test the hypothesis that reflux of pepsin into the laryngopharynx can promote carcinogenesis. STUDY DESIGN: Translational research study. METHODS: Normal human laryngeal primary epithelial cell cultures and hypopharyngeal FaDu SCC cells were exposed to human pepsin and analyzed by Human Cancer PathwayFinder and miRNA Superarrays, flow cytometry, and Western blot to determine the effect of pepsin on carcinogenesis. Laryngeal biopsy specimens taken from cancer patients and normal control subjects were analyzed for the presence of pepsin by Western blot. RESULTS: Microarray analysis demonstrated that pepsin significantly altered the expression of 27 genes implicated in carcinogenesis and also affected the expression of 22 microRNAs known to be altered in human head and neck cancers. Pepsin increased proliferation in both FaDu SCC cells and cultured normal laryngeal epithelial primary cells by increasing S phase distribution on flow cytometry analysis in a time- and dose-dependent manner. Furthermore, pepsin was detected in 60% (3/5) human laryngeal cancer biopsies, absent in all (0/5) normal control specimens. CONCLUSIONS: These data support a role for refluxed pepsin in the promotion of epithelial proliferation and carcinogenesis of the larynx and pharynx.

Pepsin in nonacidic refluxate can damage hypopharyngeal epithelial cells.

OBJECTIVES: Studies using combined multichannel intraluminal impedance with pH monitoring reveal a role for nonacidic reflux in laryngopharyngeal symptoms and injury. We have discovered that pepsin is taken up by laryngeal epithelial cells by receptor-mediated endocytosis. This finding reveals a novel mechanism by which pepsin could cause cell damage, potentially even in nonacidic refluxate. The objective of this study was to determine whether pepsin, at pH 7.4 and thus in nonacidic refluxate, causes cell damage. METHODS: Cultured hypopharyngeal epithelial (FaDu) cells were exposed to human pepsin (0.1 mg/mL) at pH 7.4 for either 1 hour or 12 hours at 37 degrees C and analyzed by electron microscopy, cytotoxicity assay, and SuperArray. RESULTS: We report mitochondrial and Golgi complex damage in cells exposed to pepsin at neutral pH, observed by electron microscopy. We also report cell toxicity of pepsin at pH 7.4, measured by a cytotoxicity assay. Furthermore, using SuperArray, we found that pepsin at pH 7.4 significantly alters the expression levels of multiple genes implicated in stress and toxicity. CONCLUSIONS: These findings are perhaps the first to explain why many patients have symptoms and injury associated with nonacidic reflux, and could have important implications for the development of new therapies for reflux, such as pepsin receptor antagonists and/or irreversible inhibitors of peptic activity.

Modes of cell death in the hypopharyngeal gland of the honey bee (Apis mellifera l).

Different modes of cell death have been revealed in the regressing hypopharyngeal glands of worker honey bees. The hypopharyngeal gland, which is well developed in young nursing bees to produce protein for larval food, was seen to regress naturally in foraging adult worker bees. A range of techniques including histology, cytochemistry, in situ TUNEL, Annexin V and Comet assays indicated that cells within the gland demonstrate progressive symptoms of apoptosis, necrosis and a vacuolar form of programmed cell death. The latter mode of cell death did not display chromatin margination, but was accompanied by an enhanced level of autophagic and hydrolytic activity in which a cytosolic source of acid phosphatase became manifest in the extra-cisternal spaces. Normal and annexin-positive cells were found to occur in the younger nursing bees, whilst necrosis and an aberrant vacuolar type of apoptosis predominated in the older foraging bees. The relevance of these results to the classification of programmed cell death is discussed.

Change in the mode of gene expression of the hypopharyngeal gland cells with an age-dependent role change of the worker honeybee Apis mellifera L.

Major proteins synthesized in the hypopharyngeal gland of the worker honeybee change from bee-milk proteins to alpha-glucosidase in accordance with the age-dependent role change of the worker bee. Previously, we showed that the gene for alpha-glucosidase is expressed specifically in the forager-bee gland [Ohashi, K., Sawata, M., Takeuchi, H., Natori, S. & Kubo, T. (1996) Biochem. Biophys. Res. Commun. 221, 380-385]. Here, we describe the isolation and analysis of cDNAs for two bee-milk 56-kDa and 64-kDa proteins. The 56-kDa protein was a glycoprotein which shared 63.2% and 56.9% amino acid sequence identities with proteins encoded by cDNA for royal-jelly-related protein 57-1 (pRJP57-1) and pRJP57-2. The 64-kDa protein cDNA was identical to pRJP57-1. Thus, these bee-milk proteins seem to form a structurally related protein family. The gene for the 64-kDa protein/RJP57-1 was expressed specifically in the nurse-bee gland, whereas that for the 56-kDa protein was expressed in both the nurse-bee and forager-bee glands. mRNAs for the 56-kDa and 64-kDa proteins were detected by in situ hybridization in a whole acinus of the nurse-bee gland, whereas mRNAs for the 56-kDa protein and alpha-glucosidase were detected in that of the forager-bee gland. Therefore, the individual secretory cells of the acinus of the hypopharyngeal gland were shown to express these genes differently with the age-dependent role change of the worker bee.