Emerging Insights into Keratin 16 Expression during Metastatic Progression of Breast Cancer
by
, , , and
Maha Elazezy
1, 
Sandra Schwentesius
1,
Luisa Stegat
1,
Harriet Wikman
1,
Stefan Werner
1,
Wael Y. Mansour
2,
Antonio Virgilio Failla
3,
Sven Peine
4,
Volkmar Müller
5,
Jean Paul Thiery
6,
Majid Ebrahimi Warkiani
7, 
Klaus Pantel
1 and
Simon A. Joosse
1,* 1
Department of Tumor Biology, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
2
Department of Radiotherapy and Radiation Oncology, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
3
UKE Microscopy Imaging Facility (UMIF), University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
4
Department of Transfusion Medicine, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
5
Department of Gynecology, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
6
Bioland Laboratory, Guangzhou Regenerative Medicine and Health Guangdong Laboratory, Guangzhou 510320, China
7
School of Biomedical Engineering, University of Technology Sydney, Sydney 2007, Australia
*
Author to whom correspondence should be addressed.
Cancers 2021, 13(15), 3869; https://doi.org/10.3390/cancers13153869
Submission received: 8 July 2021
/
Revised: 25 July 2021
/
Accepted: 26 July 2021
/
Published: 31 July 2021
Simple Summary
The mechanisms leading to tumor metastasis remain poorly understood, and therefore, phenotyping of circulating tumor cells from cancer patients may contribute to translating these mechanisms. In in silico analysis, high expression of keratin 16 was associated with higher tumor aggressiveness. According to our results, keratin 16 is a metastasis-associated protein that promotes EMT and acts as a positive regulator of cellular motility by reorganizing the actin cytoskeleton, which is the driving force behind disrupting intercellular adhesion and directional migration. In metastatic breast cancer patients, circulating tumor cells expressing keratin 16 were associated with shorter relapse-free survival. This is an important issue for future research to determine the exact function of keratin 16 in tumor dissemination and metastasis development by analyzing keratin 16 status in disseminating tumor cells. Furthermore, gaining a better knowledge of keratin 16’s biology would give crucial mechanistic insights that might lead to a unique treatment option.
Abstract
Keratins are the main identification markers of circulating tumor cells (CTCs); however, whether their deregulation is associated with the metastatic process is largely unknown. Previously we have shown by in silico analysis that keratin 16 (KRT16) mRNA upregulation might be associated with more aggressive cancer. Therefore, in this study, we investigated the biological role and the clinical relevance of K16 in metastatic breast cancer. By performing RT-qPCR, western blot, and immunocytochemistry, we investigated the expression patterns of K16 in metastatic breast cancer cell lines and evaluated the clinical relevance of K16 expression in CTCs of 20 metastatic breast cancer patients. High K16 protein expression was associated with an intermediate mesenchymal phenotype. Functional studies showed that K16 has a regulatory effect on EMT and overexpression of K16 significantly enhanced cell motility (p < 0.001). In metastatic breast cancer patients, 64.7% of the detected CTCs expressed K16, which was associated with shorter relapse-free survival (p = 0.0042). Our findings imply that K16 is a metastasis-associated protein that promotes EMT and acts as a positive regulator of cellular motility. Furthermore, determining K16 status in CTCs provides prognostic information that helps to identify patients whose tumors are more prone to metastasize.
