Immunohistochemical staining patterns of alpha-keratins in normal tissues from two reptile species: implications for characterization of squamous cell carcinomas

Abstract

BackgroundCytokeratins with epitopes in common with those of alpha (acidic and basic) mammalian keratins have been immunohistochemically demonstrated in the epidermis of reptiles. However, there are no reports of immunohistochemical staining patterns of alpha-keratins in other tissues from reptiles. Because the epithelial tumours usually retain the keratin patterns of their normal epithelial origin, it is necessary to know in advance these patterns in the major normal epithelia and organs. We used anti-alpha human keratin AE1 and AE3 monoclonal antibodies to study the staining patterns of alpha-keratins in the major normal epithelia and organs from two reptile species [the bearded dragon (Pogona vitticeps) and the loggerhead sea turtle (Caretta caretta)]. We also studied the immunolocalization of alpha-keratins in squamous cell carcinomas (SCCs) in a bearded dragon and two loggerhead turtles.ResultsAcidic alpha-keratin (AE1 positive) was detected in many of the epithelial tissues of the bearded dragons; however, the detection of basic alpha-keratin (AE3 positive) was much more limited. Alpha-keratins were detected in a greater number of tissues of loggerhead turtles compared with those observed in bearded dragons. In the bearded dragon SCC, all layers of the nests of neoplastic cells, including the cornified layer of the keratin pearls, were strongly reactive with the AE1 antibody. However, a weak reactivity using the AE3 antibody was detected in the basal and intermediate layers of these nests. In the cutaneous SCCs of both sea turtles, acidic alpha-keratin was detected in the basal and suprabasal layers, and in all of the invasive neoplastic cords, while basic alpha-keratin was mainly detected in the invasive neoplastic cords. The pattern observed in the metastases in both turtles consisted of immunohistological detection of acidic alpha-keratin in all metastatic foci, and limited or lack of detection of basic alpha-keratin.ConclusionsThis study provides, for the first time, information about the immunohistochemical staining patterns of alpha-keratins in normal tissues from bearded dragons and loggerhead sea turtles, and confirms the usefulness of AE1 and AE3 monoclonal antibodies in these reptile species. The use of these antibodies also contributed to a better characterization of SCCs in these species.

Metastasizing squamous cell carcinoma in a 50-year-old Eastern Hermann‘s tortoise (Testudo hermannii boettgeri)

“…Due to the limited availability of antibodies and protocols, only pan-cytokeratin IHC detecting both basic and acidic keratins was performed in our case. The weak immunopositivity in non-keratinized areas of the tumor could be due to poorly diff erentiated tumor cells, similar to the failed immunohistochemical detection of alpha-keratin in a poorly diff erentiated SCC in a turtle [ 32 ] . In conclusion, non-keratinized and pan-cytokeratin positive soft tissue nodules were attributed to metastasized carapacial squamous cell carcinoma with poor diff erentiation.…”

“…Immunohistochemical characterization of reptile skin has been previously demonstrated with antibodies against acidic (type I) and basic (type II) alpha-keratin in normal tissues and a series of SCC from bearded dragons ( Pogona vitticeps ) and loggerhead turtles ( Caretta caretta ) [ 32 ] . Due to the limited availability of antibodies and protocols, only pan-cytokeratin IHC detecting both basic and acidic keratins was performed in our case.…”

Histological Variants of Squamous and Basal Cell Carcinoma in Squamates and Chelonians: A Comprehensive Classification

“…Although poorly differentiated SCCs were not demonstrated in the present study, this third histological grade of conventional SCCs may be encountered in reptiles. Histological characteristics of poorly differentiated SCCs in humans include enlarged, pleomorphic nuclei with asynchronous differentiation from basal to central squamous cells, marked nuclear atypia, and frequent mitoses [ 20 , 22 ]. Keratin pearls are a highly unusual finding in poorly differentiated SCCs.…”

“…For human BCCs, infiltrating BCCs and BSCCs represent high-risk histological variants, and solid BCCs, keratotic BCCs, and superficial BCCs represent low-risk histological variants [ 18 ]. While SCCs with varying degrees of differentiation are commonly observed in reptiles as well as birds [ 21 , 22 , 23 , 24 ], studies focused on in-depth comparative assessment of the histological characteristics of these neoplasms that allow the establishment of a classification system, are lacking.…”

Melanomacrophage Centers: Comparative Histological Insights among Three Reptilian Species

“…Immunohistochemical detection of acidic alpha-keratin (AE1) and basic alpha-keratin (AE3) were Immunohistochemically demonstrated in normal tissues; Epidermis, Oesophageal epithelium, Gastric mucosa, small intestine, Liver, Tracheal epithelium, Lung, Kidney and Salt gland from bearded dragons (Pogona vitticeps) and loggerhead sea turtles (Caretta caretta). The AE1 mouse monoclonal antibody (IgG 1 isotype) (#61804; Progen Biotechnik, Heidelberg, Germany) was applied at 0.002 mg/mL (dilution 1:500), while the AE3 antibody mouse monoclonal (IgG 1 isotype) (#61806; Progen Biotechnik, Heidelberg, Germany) was applied at 0.001 mg/mL (dilution 1:1000) (Orós et al , 2018). The immuno-localization of the pituitary adenylate cyclase-activating polypeptide (PACAP) and its receptors PAC1, VPAC1, and VPAC2 was demonstrated in the lizard Podarcis sicula gastrointestinal and respiratory tissues.…”