Conformational Changes in the Rod Domain of Human Keratin 8 following Heterotypic Association with Keratin 18 and Its Implication for Filament Stability†

Prognostic value of disseminated tumor cells in unresectable pancreatic ductal adenocarcinoma: a prospective observational study

BACKGROUND

Although pancreatic ductal adenocarcinoma (PDAC) rarely metastasizes to the skeleton, disseminated tumor cells have been detected in bone marrow samples from patients with this disease. The prognostic value of such findings is currently unclear. Thus, the current study aimed to clarify the prognostic information associated with disseminated tumor cell detection in samples from patients with PDAC.

METHODS

Bone marrow aspirates were obtained from 48 patients with locally advanced (n = 11) or metastatic (n = 37) PDAC, before and after 2 months of chemotherapy. Disseminated tumor cells were detected with an mRNA panel and quantitative reverse transcription PCR. We used the highest levels measured in healthy bone marrow (n = 30) as a threshold to define the positive detection of disseminated tumor cells. Progression-free and overall survival were analyzed with Kaplan-Meier and Cox proportional hazards regression analyses.

RESULTS

Disseminated tumor cells were detected in 15/48 (31%) bone marrow samples obtained before starting chemotherapy and in 8/25 (32%) samples obtained during chemotherapy. Patients with disseminated tumor cells detected before therapy had significantly shorter progression-free (p = 0.03; HR = 2.0) and overall survival (p = 0.03; HR = 2.0), compared to those without disseminated tumor cells in the bone marrow. When restricting disseminated tumor cell detection to keratins KRT7 and KRT8, the prognostic information was substantially stronger (p = 1 × 10-6; HR = 22, and p = 2 × 10-5; HR = 7.7, respectively). The multivariable Cox regression analysis demonstrated that disseminated tumor cell detection prior to treatment had independent prognostic value. In contrast, disseminated tumor cells detected during treatment did not have prognostic value.

CONCLUSIONS

Disseminated tumor cells detected before commencing chemotherapy had prognostic value in patients with inoperable PDAC.

Cytoskeletal and extracellular matrix proteins as markers for metastatic triple negative breast cancer

OBJECTIVE

This study investigated immunohistochemical staining results of two cytoskeletal proteins (vimentin and cytokeratin-18) and two extracellular matrix proteins (fibronectin-1 and laminin-1 receptor) in different stages of triple negative breast cancer.

METHODS

Forty triple negative cancerous breast tissues from patients diagnosed as stage 2A (15), 2B (nine), 3A (10), 3B (four), and 3C (two) were included in this study and were compared with 42 normal breast tissues. Immunohistochemistry results were statistically analyzed using the t-test percent of the StatPac program.

RESULTS

The percentages of positive staining in cancerous tissues for all of the studied parameters were significantly greater than their percentages in normal tissues, except for vimentin. All cancerous tissues from patients diagnosed as stage 3A, 3B, and 3C were positive for both fibronectin-1 and laminin-1 receptor.

CONCLUSION

Fibronectin-1 and laminin-1 receptor are promising markers for stage 3 triple negative breast cancer.

The monoclonal antibody EPR1614Y against the stem cell biomarker keratin K15 lacks specificity and reacts with other keratins

Keratin 15 (K15), a type I keratin, which pairs with K5 in epidermis, has been used extensively as a biomarker for stem cells. Two commercial antibodies, LHK15, a mouse monoclonal and EPR1614Y, a rabbit monoclonal, have been widely employed to study K15 expression. Here we report differential reactivity of these antibodies on epithelial cells and tissue sections. Although the two antibodies specifically recognised K15 on western blot, they reacted differently on skin sections and cell lines. LHK15 reacted in patches, whereas EPR1614Y reacted homogenously with the basal keratinocytes in skin sections. In cultured cells, LHK15 did not react with K15 deficient NEB-1, KEB-11, MCF-7 and SW13 cells expressing only exogenous K8 and K18 but reacted when these cells were transduced with K15. On the other hand, EPR1614Y reacted with these cells even though they were devoid of K15. Taken together these results suggest that EPR1614Y recognises a conformational epitope on keratin filaments which can be reconstituted by other keratins as well as by K15. In conclusion, this report highlights that all commercially available antibodies may not be equally specific in identifying the K15 positive stem cell.

Externalized Keratin 8: A Target at the Interface of Microenvironment and Intracellular Signaling in Colorectal Cancer Cells

Accumulating evidence supports the remarkable presence at the membrane surface of cancer cells of proteins, which are normally expressed in the intracellular compartment. Although these proteins, referred to as externalized proteins, represent a highly promising source of accessible and druggable targets for cancer therapy, the mechanisms via which they impact cancer biology remain largely unexplored. The aim of this study was to expose an externalized form of cytokeratin 8 (eK8) as a key player of colorectal tumorigenesis and characterize its mode of action. To achieve this, we generated a unique antagonist monoclonal antibody (D-A10 MAb) targeting an eight-amino-acid-long domain of eK8, which enabled us to ascertain the pro-tumoral activity of eK8 in both KRAS-mutant and wild-type colorectal cancers (CRC). We showed that this pro-tumoral activity involves a bidirectional eK8-dependent control of caspase-mediated apoptosis in vivo and of the plasminogen-induced invasion process in cellulo. Furthermore, we demonstrated that eK8 is anchored at the plasma membrane supporting this dual function. We, therefore, identified eK8 as an innovative therapeutic target in CRC and provided a unique MAb targeting eK8 that displays anti-neoplastic activities that could be useful to treat CRC, including those harboring KRAS mutations.

Isolation and characterization of trophoblast-derived stem-like cells from peri-implantation porcine embryos

In mammals, the trophoblast lineage of the embryo is specified before attachment/implantation to become the fetal portion of the placenta. Trophoblast-derived cells were isolated and cultured from day 10 and day 13 porcine embryos and were grown in vitro in a defined, serum-free culture medium for over 2 years without showing any signs of senescence. However, trophoblast-derived cells placed into serum-containing medium rapidly senesce and fail to proliferate. Semiquantitative and quantitative gene expression analyses of cells in culture from 0 to 30 days confirmed the presence (and relative abundance) of mRNA transcripts from genes involved in trophoblast function (CDX2, TEAD4, CYP17A1, HSD17B1, FGFR2, PLET, HAND1) as well as some genes known to mediate pluripotency (POU5F1, KLF4, CMYC). Protein immunolocalization demonstrated expression of both trophoblast and mesenchymal cell markers. DNA methylation patterns in promoters of three critical developmental genes (HAND1, KLF4, TEAD4) did not change appreciably over 4 months of culture in vitro. It was demonstrated that these trophoblast-derived cells are easily stably transfected with an exogenous transgene (eGFP) by a variety of methods, and show the ability to survive and to be passaged repeatedly after transfection. In summary, early embryonic porcine trophoblast-derived cells have demonstrated unique characteristics, which means they could be used as valuable tools for laboratory work. Anticipated applications include the study of trophoblast physiology as well as possible solutions for improving efficiency of transgenesis by somatic cell nuclear transfer and for pluripotency reprogramming of cells.

Disseminated tumor cells in pancreatic cancer-an independent prognosticator of disease progression and survival

Pancreatic cancer is one of the most devastating cancers with a 6-month median survival and a 5-year survival rate of 3-5%. Still important aspects of its aggressive biology remain elusive and advanced therapeutic regimens have not been substantially successful. We investigated the prognostic role of disseminated tumor cells (DTC) in bone marrow, a reservoir for early DTC potentially contributing to metastatic progression, of pancreatic cancer patients. After exclusion of patients with different postsurgery diagnosis or missing DTC status (n = 40) a total of 175 patients remained for final analyses. One-hundred and nineteen patients were male and 96 female with a median age of 67 years, 96 patients underwent complete resection. Bone marrow aspirates taken at primary surgery were analyzed for DTC by an immunocytochemical cytokeratin assay and correlated to survival data. Overall 13.7% of patient samples (24/175) harbored DTC in their bone marrow. Histopathological parameters did not correlate significantly. Univariate survival analysis revealed a borderline significant correlation between DTC and decreased progression-free survival (p = 0.069), and was significant for overall survival (p = 0.036). Regarding patients with resected tumors, the respective p-values were 0.058 for progression-free and 0.016 for overall survival. Importantly, the prognostic influence was independent from other risk factors as shown by multivariate analyses for progression-free (p = 0.030, HR: 2.057; CI (95%): 1.073-3.943) and overall survival (p = 0.006, HR: 2.283; CI (95%): 1.260-4.135). The presence of DTC in bone marrow is a strong and independent prognostic factor of survival in patients with pancreatic cancer. Thus, bone-targeting may be a new future therapeutic option for DTC-positive patients.

Detection and clinical relevance of early disseminated breast cancer cells depend on their cytokeratin expression pattern

The factors determining the clinical relevance of disseminated tumor cells (DTC) in breast cancer patients are largely unknown. Here we compared the specificity and clinical performance of two antibodies frequently used for DTC detection. Reactivities of antibodies A45-B/B3 (A45) and AE1/AE3 (AE) for selected cytokeratins (CK) were assessed by 2-DE Western Blot analysis. Using these antibodies bone marrow aspirates from 391 breast cancer patients (M(0), pT1-3, pN0-3) were screened for the presence of DTC. To obtain prognostic information, patients were followed up over a median of 83 months for time to relapse and 99 months for time to death. Among the analyzed CK, AE detected CK5, CK7, CK8, and CK19, whereas A45 recognized CK7 and CK18. In total, 24 of 391 patients (6.1%) were DTC-positive for A45, and 41 (10.5%) for AE. Although concordance between the two antibodies was 84.4%, overlap among positive cases was only 3.2%. DTC-positivity with AE and A45 was more frequent in patients of higher nodal status (P=0.019 and P=0.036, respectively). Nearly all patients with A45-positive DTC had hormone receptor-positive tumors (23/24), while detection of AE-positive DTC was more frequent among hormone receptor negative patients (P=0.006). Survival analyses of all patients revealed shorter distant disease-free survival (P=0.039) for patients with A45-positive DTC, whereas the prognostic relevance of AE-positive DTC was restricted to node-positive patients. The clinical utility of immunocytochemical (ICC) DTC detection depends on the anti-CK antibody used, which may reflect the complex CK composition of DTC.

Nanoscale surface topography enhances cell adhesion and gene expression of madine darby canine kidney cells

Substrate topography is one of the key factors that influence cell behavior, such as cell attachment, adhesion, proliferation and differentiation. In the present work, nanostructures were produced on polystyrene Petri dish by polarized laser irradiation with the wavelength of 266 nm and the energy of 3.0 mJ/cm2. Cell adhesion, growth and gene expression of Madine darby canine kidney (MDCK) cells cultured on smooth and nanogrooved substrates were investigated. The results indicated that cells preferred to adhere and grow on nanogrooved substrate. The distribution of cell cycle for cells on smooth substrates was different from that on nanogrooved substrate. The percentage of G1 phase cells on nanogrooved substrate (48.6 +/- 1.4%) was lower than that on smooth substrate (57.6 +/- 4.4%), while the percentage of cells on nanogrooved substrate in S (30.2 +/- 0.5%) and G2/M (21.2 +/- 1.1%) phase was higher than those on smooth substrate (25.1 +/- 1.5% and 17.3 +/- 3.3%, respectively). Moreover, the gene expression of cyclin D1 and keratin 18, which was examined by semi-quantitative reverse transcription polymerase chain reaction (RT-PCR), was significantly enhanced by nanogrooves, with an increase of cyclin D1 mRNA by 98% and an increase of keratin 18 mRNA by 75%. In conclusion, the nanogrooved surface features on polystyrene could alter cell cycle and enhance gene expression of cyclin D1 and keratin 18 in MDCK cells, which partly explained the increased cell adhesion and growth on nanogrooved substrate.

Prognostic impact of Thomsen-Friedenreich tumor antigen and disseminated tumor cells in the bone marrow of breast cancer patients

PURPOSE

The Thomsen-Friedenreich antigen (TF, CD176) is a specific oncofetal carbohydrate epitope (Gal beta1-3GalNAc alpha-O-Ser/Thr) expressed on the surface of various carcinomas. It mediates endothelium adhesion and formation of metastases. As it also causes immune response, its prognostic impact is indeterminate. The presence of disseminated tumor cells in the bone marrow of breast cancer patients (DTC-BM) indicates worse prognosis. We examined the expression of TF in primary breast cancer tissue of 265 patients with known BM status at the time of first diagnosis.

METHODS

BM aspiration, cytospin preparation and immunocytochemical staining with the anti-Cytokeratin antibody A45 B/B3 was done following a standardised protocol. TF expression was examined immunohistochemically on Tissue Micro Arrays (TMA) with the anti-TF antibody A78-G/A7. Evaluation was done using the immunoreactive score (IRS).

RESULTS

Median IRS for TF expression was 2 (0-12). 68 of 265 patients (25.7%) showed DTC-BM with a median of 2/2 x 10(6) cells (1-1500). There was no correlation between TF expression and DTC-BM. After a median follow up of 60.1 months (7-119), the detection of DTC-BM showed prognostic significance for overall survival (OS, p = 0.034), whereas TF positivity (IRS > 2) indicated prolonged disease-free (p = 0.01), distant disease-free (p = 0.005), and overall survival (p = 0.005).

DISCUSSION

Patients with TF-positive tumors had a significantly better prognosis. Dissemination routes, TF-mediated metastasis formation, and the immunogeneity of TF might determine the prognostic impact of TF expression in different tumor entities. Further characterisation of primary tumors and DTC-BM could help to improve the biological understanding of metastases and develop targeted therapies.

Epithelial vs myofibroblast differentiation in immortal rat lung cell lines—modulating effects of bleomycin

Two alveolar epithelial cell lines R3/1 and L2 were screened by immunocytochemical and RT-PCR analysis of epithelial and mesenchymal/contractile marker proteins. R3/1 and L2 cells were tested for their sensitivity to bleomycin (BLM), an anticancer drug, which is proposed to induce changes in lung cell differentiation. Both epithelial cell lines exhibited a mixed phenotype consisting of epithelial (E-cadherin, aquaporin-5 and cytokeratin 8) and myofibroblast-like (vimentin, alpha-SMA and caveolin-3) properties suggesting that the cell lines are arrested in vitro at a certain developmental stage during epithelial-mesenchymal transition (EMT). BLM treatment of R3/1 cells resulted in a partial reversal of this process modifying the cells in an epithelial direction, e.g., upregulation of E-cadherin, aquaporin-5 and other lung epithelial antigens at the mRNA and protein level. L2 cells showed similar alterations following BLM exposure.Immunohistochemical investigation of lung tissue from two different animal models of BLM-induced fibrosis (mouse and rat), revealed no signs of EMT, e.g., myofibroblastic differentiation of alveolar epithelial cells in situ. Immunohistological analysis of tissue samples of the rat model showed a heterogeneous population of myofibroblasts (alpha-SMA+/caveolin-3+, alpha-SMA-/caveolin-3+, and alpha-SMA+/caveolin-3-). These results suggest that BLM, on one hand, induces fibrosis and on the other hand possibly suppresses EMT during fibrogenesis.

Keratin 8/18 breakdown and reorganization during apoptosis

Monoclonal antibodies that specifically recognize caspase cleaved K18 fragments or specific (phospho)epitopes on intact K8 and K18 were used for a detailed investigation of the temporal and causal relationship of proteolysis and phosphorylation in the collapse of the keratin cytoskeleton during apoptosis. Caspases involved in the specific proteolysis of keratins were analyzed biochemically using recombinant caspases and specific caspase inhibitors. Finally, the fate of the keratin aggregates was analyzed using the M30-ApoptoSense trade mark Elisa kit to measure shedding of caspase cleaved fragments into the supernatant of apoptotic cell cultures. From our studies, we conclude that C-terminal K18 cleavage at the (393)DALD/S site is an early event during apoptosis for which caspase 9 is responsible, both directly and indirectly by activating downstream caspases 3 and 7. Cleavage of the L1-2 linker region of the central alpha-helical rod domain is responsible for the final collapse of the keratin scaffold into large aggregates. Phosphorylation facilitates formation of these aggregates, but is not crucial. K8 and K18 remain associated in heteropolymeric aggregates during apoptosis. At later stages of the apoptotic process, that is, when the integrity of the cytoplasmic membrane becomes compromised, keratin aggregates are shed from the cells.