Keratin 17 Expression Research Articles

Knockdown of KRT17 by siRNA induces antitumoral effects on gastric cancer cells.

Keratin 17 (KRT17) was shown to be an important molecular marker for predicting the carcinogenesis, progression, and prognosis of various cancer types. Our previous studies identified KRT17 as a possible biomarker for gastric cancer by gene microarray, with an elevated expression that occurred early during tumorigenesis and increased during tumor progression. Based on these findings, we aimed to investigate KRT17 biological functions in gastric adenocarcinoma and its possible use as a rational molecular target for anticancer therapy. We used RNA interference-mediated knockdown of KRT17 expression and analyzed the effects on cell proliferation, cell migration, and signal transduction in two gastric cell lines (AGS and NCI-N87) in vitro and on xenograft growth in vivo. The functional analysis of KRT17 knockdown cell lines showed a decreased cell proliferation (with 42.36%±3.2%) and migration ability (with 37.2%±6.2%) relative to scrambled siRNA control. The in vivo tumorigenicity on nude mice exhibited a significant decrease in tumor weight with 69.14% in xenografts obtained from AGS cells and 84.43% in xeno-NCI-N87 tumors. The analysis on KRT17 knockdown outcome on intracellular signaling identifies AKT/mTOR as the main affected pathway that sustains proliferation and survival, and also the AMPKα1/CREB pathway that was recently shown to induce organ protection and antiinflammatory response. Our results highlight KRT17 as a possible biomarker in gastric cancer promoting tumor growth, motility, and invasion, and suggest that KRT17 can be a valuable molecular target for development of anti-gastric cancer-specific therapies.

Abstract 1841: Dissecting gene expression programs that define tumor aggression and patient outcome in pancreatic cancer

Abstract By the year 2020, pancreatic cancer (PDAC) is projected to be the second leading cause of cancer deaths in the United States. Current systemic therapies offer limited survival advantages in subgroups of patients, suggesting underlying biological differences in this deadly cancer. Our lab has recently identified keratin-17 (K17) gene expression as a prognostic and predictive biomarker in PDAC. Furthermore, we found that K17 acts as an oncoprotein by promoting degradation of tumor suppressor p27KIP1, while knockdown of K17 limits tumor size and sensitizes cancer cells to chemotherapy agents. Together, these findings suggest that targeting K17 expression in PDACs may increase patient survival and response to treatment. The factors that lead to increased K17 gene expression in only a subset of PDAC cases, however, are unknown. K17 is expressed in embryonic ectoderm and aberrantly induced in keratinocytes from psoriasis patients through paracrine signaling from the microenvironment. To determine how K17 gene expression is upregulated in PDAC, we tested the effects of two major contributing factors in PDAC pathogenesis: driver mutations and inflammatory mediators present in tumor microenvironment. Using in vitro and in vivo loss- and gain-of function approaches, we modulated oncogene expression in and performed acute cytokine treatments on cells to test for changes in K17 gene expression. K17 expression was evaluated by qRT-PCR and western blot. We found that forced expression of oncogenes like KRASG12D, Q61K or TP53R248W significantly increase K17 expression, yet these cell-autonomous factors are not sufficient to explain K17 gene expression in PDACs. In addition, we found that pro-inflammatory cytokines, typically released by helper T cells, induce a strong increase in K17 gene expression. Together these findings suggest that K17 gene expression across otherwise clinically identical PDAC cases may be explained by early transformation events and maintained by positive feedback loops associated with patient specific adaptive immune response. Ongoing studies are seeking to test the combined effects of genetic and paracrine events in K17 expression, and understand the signaling pathways and transcription factors downstream of these inducing factors. Ultimately, insight into the mechanisms that mediate K17 overexpression in PDACs could help guide future research to develop K17 as a potential therapeutic target. Citation Format: Danielle J. Fassler, Luisa F. Escobar-Hoyos, Kenneth R. Shroyer. Dissecting gene expression programs that define tumor aggression and patient outcome in pancreatic cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1841.

Genetic ablation of caspase-7 promotes solar-simulated light-induced mouse skin carcinogenesis: the involvement of keratin-17.

Solar ultraviolet irradiation is an environmental carcinogen that causes skin cancer. Caspase-7 is reportedly expressed at reduced levels in many cancers. The present study was designed to examine the role of caspase-7 in solar-simulated light (SSL)-induced skin cancer and to elucidate its underlying molecular mechanisms. Our study revealed that mice with genetic deficiency of caspase-7 are highly susceptible to SSL-induced skin carcinogenesis. Epidermal hyperplasia, tumor volume and the average number of tumors were significantly increased in caspase-7 knockout (KO) mice compared with SKH1 wild-type mice irradiated with SSL. The expression of cell proliferation markers, such as survivin and Ki-67, was elevated in SSL-irradiated skin of caspase-7 KO mice compared with those observed in SSL-exposed wild-type SKH1 mouse skin. Moreover, SSL-induced apoptosis was abolished in skin from caspase-7 KO mice. Two-dimensional gel electrophoresis, followed by matrix-assisted laser desorption/ionization-time-of-flight analysis of skin tissue lysates from SSL-irradiated SKH1 wild-type and caspase-7 KO mice revealed an aberrant induction of keratin-17 in caspase-7 KO mice. Immunohistochemical analysis of skin tumors also showed an increase of keratin-17 expression in caspase-7 KO mice compared with SKH1 wild-type mice. The expression of keratin-17 was also elevated in SSL-irradiated caspase-7 KO keratinocytes as well as in human basal cell carcinomas. The in vitro caspase activity assay showed keratin-17 as a substrate of caspase-7, but not caspase-3. Overall, our study demonstrates that genetic loss of caspase-7 promotes SSL-induced skin carcinogenesis by blocking caspase-7-mediated cleavage of keratin-17.

Keratin 17 in premalignant and malignant squamous lesions of the cervix: proteomic discovery and immunohistochemical validation as a diagnostic and prognostic biomarker

Most previously described immunohistochemical markers of cervical high-grade squamous intraepithelial lesion (HSIL) and squamous cell carcinoma may help to improve diagnostic accuracy but have a minimal prognostic value. The goals of the current study were to identify and validate novel candidate biomarkers that could potentially improve diagnostic and prognostic accuracy for cervical HSIL and squamous cell carcinoma. Microdissected tissue sections from formalin-fixed paraffin-embedded normal ectocervical squamous mucosa, low-grade squamous intraepithelial lesion (LSIL), HSIL and squamous cell carcinoma sections were analyzed by mass spectrometry-based shotgun proteomics for biomarker discovery. The diagnostic specificity of candidate biomarkers was subsequently evaluated by immunohistochemical analysis of tissue microarrays. Among 1750 proteins identified by proteomic analyses, keratin 4 (KRT4) and keratin 17 (KRT17) showed reciprocal patterns of expression in the spectrum of cases ranging from normal ectocervical squamous mucosa to squamous cell carcinoma. Immunohistochemical studies confirmed that KRT4 expression was significantly decreased in squamous cell carcinoma compared with the other diagnostic categories. By contrast, KRT17 expression was significantly increased in HSIL and squamous cell carcinoma compared with normal ectocervical squamous mucosa and LSIL. KRT17 was also highly expressed in immature squamous metaplasia and in endocervical reserve cells but was generally not detected in mature squamous metaplasia. Furthermore, high levels of KRT17 expression were significantly associated with poor survival of squamous cell carcinoma patients (Hazard ratio=14.76, P=0.01). In summary, both KRT4 and KRT17 expressions are related to the histopathology of the cervical squamous mucosa; KRT17 is highly overexpressed in immature squamous metaplasia, in HSIL, and in squamous cell carcinoma and the level of KRT17 in squamous cell carcinoma may help to identify patients who are at greatest risk for cervical cancer mortality.