Keratin expression in the normal anal canal

Keratin intermediate filaments in the colon: guardians of epithelial homeostasis

Keratin intermediate filament proteins are major cytoskeletal components of the mammalian simple layered columnar epithelium in the gastrointestinal tract. Human colon crypt epithelial cells express keratins 18, 19 and 20 as the major type I keratins, and keratin 8 as the type II keratin. Keratin expression patterns vary between species, and mouse colonocytes express keratin 7 as a second type II keratin. Colonic keratin patterns change during cell differentiation, such that K20 increases in the more differentiated crypt cells closer to the central lumen. Keratins provide a structural and mechanical scaffold to support cellular stability, integrity and stress protection in this rapidly regenerating tissue. They participate in central colonocyte processes including barrier function, ion transport, differentiation, proliferation and inflammatory signaling. The cell-specific keratin compositions in different epithelial tissues has allowed for the utilization of keratin-based diagnostic methods. Since the keratin expression pattern in tumors often resembles that in the primary tissue, it can be used to recognize metastases of colonic origin. This review focuses on recent findings on the biological functions of mammalian colon epithelial keratins obtained from pivotal in vivo models. We also discuss the diagnostic value of keratins in chronic colonic disease and known keratin alterations in colon pathologies. This review describes the biochemical properties of keratins and their molecular actions in colonic epithelial cells and highlights diagnostic data in colorectal cancer and inflammatory bowel disease patients, which may facilitate the recognition of disease subtypes and the establishment of personal therapies in the future.

Cytokeratin 7 in Oropharyngeal Squamous Cell Carcinoma: A Junctional Biomarker for Human Papillomavirus-Related Tumors

Background: Human papillomavirus (HPV)-related oropharyngeal squamous cell carcinoma (SCC) represents a distinct subgroup of head and neck tumors. We analyze the expression of cytokeratin 7, a junctional biomarker with a SEQIKA fragment, which stabilizes HPV-16 E7 transcripts, in oropharyngeal SCCs.Methods: Archived tumor specimens and epidemiologic data were collected from patients with oropharyngeal SCCs over 10 years. Briefly, DNA was extracted from tissue blocks, and HPV testing was carried out using SPF10 HPV PCR and INNO-LiPA HPV Genotyping. Immunohistochemical staining for CK7 and p16ink4a was performed on the Ventana BenchMark Ultra Immunostainer. Analysis was by light microscopy using the H-score. CK7 expression was correlated with epidemiologic data, p16ink4a positivity, and HPV status using SPSS.Results: CK7 expression was observed specifically and uniformly in the tonsillar crypt epithelium of normal tonsils and tumor specimens. There were 226 cases of oropharyngeal SCCs, with 70 demonstrating both HPV and p16 positivity. Of 216 cases evaluated for CK7, 106 demonstrated some positivity, whereas H-score > 60 was seen in 55 of these. CK7 H-score > 60 was significantly associated with tonsillar subsite and HPV and p16 positivity.Conclusions: An association between CK7 and HPV has been demonstrated. CK7-expressing tonsillar crypt cells potentially represent an oropharyngeal subsite susceptible to HPV-related SCC.Impact: Along with the cervix and anorectum, specific oropharyngeal expression of CK7 in a site predisposed to HPV-related tumors may suggest a role for CK7 in the pathogenesis of this subgroup of tumors. Further research is warranted to characterize the association between CK7 and HPV-related head and neck SCC. Cancer Epidemiol Biomarkers Prev; 26(5); 702-10. ©2017 AACR.

Microanatomy of the cervical and anorectal squamocolumnar junctions: a proposed model for anatomical differences in HPV-related cancer risk

Human papilloma virus (HPV) infection causes cancers and their precursors (high-grade squamous intraepithelial lesions) near cervical and anal squamocolumnar junctions. Recently described cervical squamocolumnar junction cells are putative residual embryonic cells near the cervical transformation zone. These cells appear multipotential and share an identical immunophenotype (strongly CK7-positive) with over 90% of high-grade squamous intraepithelial lesions and cervical carcinomas. However, because the number of new cervical cancers discovered yearly world wide is 17-fold that of anal cancer, we posed the hypothesis that this difference in cancer risk reflects differences in the transition zones at the two sites. The microanatomy of the normal anal transformation zone (n=37) and topography and immunophenotype of anal squamous neoplasms (n=97) were studied. A discrete anal transition zone was composed of multilayered CK7-positive/p63-negative superficial columnar cells and an uninterrupted layer of CK7-negative/p63-positive basal cells. The CK7-negative/p63-positive basal cells were continuous with-and identical in appearance to-the basal cells of the mature squamous epithelium. This was in contrast to the cervical squamocolumnar junction, which harbored a single-layered CK7-positive/p63-negative squamocolumnar junction cell population. Of the 97 anal intraepithelial neoplasia/squamous cell carcinomas evaluated, only 27% (26/97) appeared to originate near the anal transition zone and only 23% (22/97) were CK7-positive. This study thus reveals two fundamental differences between the anus and the cervix: (1) the anal transition zone does not harbor a single monolayer of residual undifferentiated embryonic cells and (2) the dominant tumor immunophenotype is in keeping with an origin in metaplastic (CK7-negative) squamous rather than squamocolumnar junction (CK7-positive) epithelium. The implication is that, at birth, the embryonic cells in the anal transition zone have already begun to differentiate, presenting a metaplasia that-similar to vaginal and vulvar epithelium-is less prone to HPV-directed carcinogenesis. This in turn underscores the link between cancer risk and a very small and discrete population of vulnerable squamocolumnar junction cells in the cervix.

Immunophenotypic Characterization of Anal Gland Carcinoma: Loss of p63 and Cytokeratin 5/6

Anal gland carcinoma (AGC) is a rare perianal invasive cancer composed of tubular glands lined by cuboidal epithelium. The clinical features and histogenesis of AGC are not well understood and its origin from anal glands is often difficult to prove. Little is known about immunophenotypic features of AGC that could be useful in establishing the diagnosis. This study evaluated the immunohistochemical profile of 2 cases of AGC in comparison to anal glands from 11 hemorrhoidectomy specimens. Sections from the specimens were routinely processed and immunostained using commercial antibodies to cytokeratin (CK) 7, CK20, CK5/ 6, p63, CDX2, smooth muscle actin, calponin, heavy chain smooth muscle myosin, p53, and p16. In case 1 of AGC, radiation and chemotherapy preceded an abdominoperineal resection. In biopsies from this case, the neoplastic anal glands had a tubular pattern, whereas most glands in the resection specimen exhibited mucinous features. The histologic pattern in case 2 was tubular. Normal anal glands showed immunoreactivity for myoepithelial and basal cell markers CK5/6 and p63 in basal and parabasal cell layers and for CK7 in superficial cell layers. In contrast, both cases of AGC were negative for CK5/6 and p63 and were diffusely positive for CK7. Normal glands and both cases of AGC were negative for the intestinal differentiation marker CDX2, CK20, smooth muscle actin, calponin, smooth muscle myosin heavy chain, p16, and p53. Our data suggest that loss of p63 and CK5/6 expression is a feature of AGC. Anal gland carcinoma shares negativity for CDX2 and CK7+/CK20− profile with normal anal glands. No evidence of myoepithelial cells was found in normal or malignant anal glands. These data may be useful in establishing the diagnosis of AGC.

Anal canal adenocarcinoma with MUC5AC expression suggestive of anal gland origin

Anal canal adenocarcinomas arising in the anal ducts or glands are very rare neoplasms, and few useful immunohistochemical markers of these carcinomas are known to date. A 57-year-old man presented with anal bleeding, difficulty of defecation, and anal pain. Macroscopic findings of the surgically resected material showed circular stenosis of the anal canal. The mucosal surface was generally intact, but focal ulceration was seen. Microscopically, the proliferation of adenocarcinoma cells with mucin production was observed in the submucosal and muscular layers. The special stains of periodic acid-Schiff (PAS) and Alcian blue confirmed the presence of neutral and acid mucin. Immunohistochemically, normal rectal-type mucosa and normal anal ducts/glands showed the patterns of cytokeratin 7 (CK7)(-)/CK19(+, focal)/MUC5AC(-) and CK7(+, diffuse)/CK19(+, diffuse)/MUC5AC(+, focal), respectively, and neoplastic cells showed the pattern of CK7(+, diffuse)/CK19(+, diffuse)/MUC5AC(+, focal). Finally, our preliminary report suggests that the immunohistochemical combination of CK7, CK19, and MUC5AC may be an available marker for adenocarcinoma of anal ducts/glands origin.

Prognostic factors in anal carcinoma

The pathologist's role in the evaluation of patients with anal squamous carcinoma is now largely restricted to establishing the diagnosis on small biopsies. Staging is performed by imaging techniques and grading is uncertain as the biopsy may not be representative of the whole tumour. Histological subtyping is unreliable and has not been proven to be of prognostic significance. A considerable effort resulting in nearly 50 reports on cytogenetic, flow cytometric, immunohistochemical and other investigations has given new insight into pathogenesis but little guidance with regard to the individual prognosis or choice of treatment. It is concluded that future research should concentrate on larger, probably multicentre series using standardised methods and criteria for evaluation.

Anal gland carcinoma

BACKGROUND

Anal gland carcinoma is a rare entity. The authors conducted a joint study of cases coded as definite or possible anal gland carcinoma from the archives of the Armed Forces Institute of Pathology and the Canadian Reference Center for Cancer Pathology.

METHODS

Seven cases of potential anal gland carcinoma were identified from the Canadian files and 12 from the Armed Forces Institute of Pathology archives. Of these 19 cases, 14 had adequate material to allow clinical, histologic, and immunohistochemical analysis.

RESULTS

Seven of these 14 cases met a modified World Health Organization (WHO) definition of anal gland carcinoma. The mean age of these patients was 66 years (range, 60-72 years), with a male-to-female ratio of 6:1. The tumors were composed of haphazardly dispersed, small glands with scant mucin production that invaded the wall of the anorectal area with no obvious intraluminal component observed clinically or microscopically. Immunohistochemical studies were performed on all seven of these cases, revealing cytokeratin (CK) 7+/CK 20- expression in six cases, and CK 7+/CK 20+ expression in one case. The remaining seven cases showed no intraluminal component but did not meet a modified WHO definition of anal gland carcinoma. This group included three mucinous adenocarcinomas (two clinically arising in anal fistulas), all of which were CK 7+/CK 20+, and a rectal-type adenocarcinoma that was CK 7-/CK 20+. There was also a tumor interpreted as probable rectal-type adenocarcinoma that was CK 7+/CK 20+, and a tumor interpreted as probable squamous cell carcinoma that was CK 7-/CK 20-. The seventh tumor in this group, which could not be classified, was CK 7+/CK 20-.

CONCLUSIONS

A useful and discriminating definition of anal gland carcinoma is an anal canal tumor composed of haphazardly dispersed, small glands with scant mucin production invading the wall of the anorectal area without an intraluminal component. The glands are positive for CK 7.

Tissue specific HPV expression and downregulation of local immune responses in condylomas from HIV seropositive individuals

OBJECTIVE

To study the effect of tissue specific human papillomavirus (HPV) expression and its effect on local immunity in condylomas from HIV positive individuals.

METHODS

Biopsy specimens of eight penile and eight perianal condylomas from HIV seropositive individuals were analysed. Expression of viral genes (HIV-tat and HPV E7 and L1) was determined by RT-PCR. The status of local immunity also was determined by RT-PCR by measuring CD4, CD8, CD16, CD1a, HLA-DR, and HLA-B7 mRNA levels in the tissues. Differentiation was determined by measuring involucrin, keratinocyte transglutaminase, as well as cytokeratins 10, 16, and 17. Proliferation markers such as PCNA and c-myc were also determined.

RESULTS

The transcription pattern of HPV in perianal condylomas, which preferentially expressed the early (E7) gene, was different from that of penile condylomas, which primarily expressed the late (L1) gene. This transcription pattern is in good correlation with the keratinisation and differentiation patterns of the two epithelia: perianal biopsies preferentially expressed K16 and K17 while penile warts mainly expressed K10, markers of parakeratotic and orthokeratotic epithelia, respectively. Perianal biopsies also showed a higher degree of proliferation (PCNA and c-myc). Interestingly, transcription of HIV-tat was also higher in perianal than in penile biopsies. A high degree of local immunodeficiency was observed in perianal biopsies--that is, levels of CD4, CD16, and CD1a mRNAs were significantly lower. A negative correlation between CD1a (Langerhans cells) levels and HPV E7 levels was established. HPV E7 levels positively correlated with HIV-tat levels. Perianal tissues demonstrated more CD1a depression and tat associated HPV upregulation.

CONCLUSION

HIV influences the expression of HPV genes resulting in local immunosuppression that might lead to an inappropriate immune surveillance of viral infection. Also, tissue type is an important factor in controlling viral transcription in a differentiation dependent manner. These findings may explain the higher rate of dysplasia and neoplasia in the perianal area.

The cytoskeleton and disease: genetic disorders of intermediate filaments

Specialized cytoskeletons play many fascinating roles, including mechanical integrity and wound-healing in epidermal cells, cell polarity in simple epithelia, contraction in muscle cells, hearing and balance in the inner ear cells, axonal transport in neurons, and neuromuscular junction formation between muscle cells and motor neurons. These varied functions are dependent upon cytoplasmic networks of actin microfilaments (6 nm), intermediate filaments (10 nm) and microtubules (23 nm), and their many associated proteins. In this chapter, I review what is known about the cytoskeletons of intermediate filaments and their associated proteins. I focus largely on epidermal cells, which devote most of their protein-synthesizing machinery to producing an extensive intermediate filament network composed of keratin. Recent studies have shown that many of the devastating human disorders that arise from degeneration of this cell type have as their underlying basis either defects in the genes encoding keratins or abnormalities in keratin IF networks. I discuss what we know about the functions of IFs, and how the link to genetic disease has enhanced this understanding.