Novel model of triple-negative breast cancer produces viable circulating tumor cells and rapid lung metastasis for functional testing in vivo

Breast cancer metastases are the main reason for women´s highest cancer mortality. Even though tumor cell dissemination via circulating tumor cells (CTC) released from the primary site is a very ineffective process, distant metastases appear in 46% of triple-negative breast cancer (TNBC) patients corresponding to the disease aggressiveness. Laboratory models for functional testing which mimic the spread of metastatic cells are needed for efficient investigation of the underlying mechanisms and therapeutic intervention. Here, we describe novel isogenic variants LMC3 and CTC3 of human TNBC cell line MDA-MB-231 that were derived by repeated injection of tumor cells into the tail vein of immunodeficient mice and subsequent selection of metastatic cells from lung metastases. These variants have increased migration potential, altered expression profiles, and elevated tumorigenic potential. Moreover, cell line CTC3 readily produces metastases in the lungs and bone marrow and detectable viable circulating tumor cells in the blood. This model enables rapid and cost-efficient strategies for biomarker exploration and novel intervention approaches to limit the CTC presence in the blood and hence tumor dissemination.

Effect of the PARP inhibitor veliparib on germ cell tumor cell lines

Germ cell tumors (GCTs) usually represent efficiently curable neoplasms due to their chemosensitivity to platinum-based therapeutic regimen. However, some patients develop therapeutic resistance and succumb to their disease. Novel therapeutic approaches are therefore needed for these patients. It has previously been demonstrated that poly (ADP-ribose) polymerase (PARP) expression is upregulated in GCTs compared with normal testis tissue. Therefore, PARP expression was analyzed in GCT cell lines and xenografts and it was examined whether its inhibition by veliparib can reverse cisplatin-resistance. Its expression was analyzed in sensitive and cisplatin-resistant variants (referred to as CisR throughout the manuscript) GCT cell lines and xenografts using quantitative PCR, western blotting and immunohistochemistry. The present study investigated whether the combination of cisplatin with the PARP inhibitor veliparib increased the cytotoxic effect of cisplatin in vitro using a luminescent viability assay and an immunodeficient mouse model in vivo. PARP expression was observed in all tested cell lines, with the highest expression in embryonal carcinoma (EC) cell lines and xenografts. Low or no expression was detected in the JEG-3 choriocarcinoma cell line pairs and xenografts. The combination of veliparib and cisplatin or carboplatin was examined in the cisplatin-resistant NTERA-2 CisR and NCCIT CisR EC cell lines and synergistic effects were observed in NTERA-2 CisR cells. However, in vivo analysis did not confirm this synergy. The present data indicated PARP expression in GCT cell lines and xenografts. However, veliparib failed to increase the cytotoxicity of platinum-based drugs. Therefore, further research is warranted to effectively inhibit PARP using different PARP inhibitors or other drug combinations.

Phase II study of disulfiram (D) and cisplatin (P) in refractory germ cell tumors (GCTs)

e17013

Background: Multiple relapsed/refractory GCTs patients have extremely poor prognosis, therefore, new treatment strategies are warranted. Previously, we showed, that cisplatin resistant testicular GCTs overexpress aldehyde-dehydrogenase (ALDH) isoforms and inhibition of ALDH activity by disulfiram is associated with reconstitution of cisplatin sensitivity in vitro as well as in animal model. This study aimed to determine the efficacy and toxicity of ALDH inhibitor disulfiram in combination with cisplatin in patients with multiple relapsed/refractory germ cell cancer. Methods: Twelve patients with multiple relapsed/refractory GCTs were enrolled in the phase II study from May 2019 to September 2021. All patients were pretreated with at least 2 cisplatin-based therapies (median 4, range 2 – 7); 6 tumors (50.0%) were absolutely refractory to cisplatin and 9 patients (75.0%) had visceral non-pulmonary metastases. Disulfiram was administered at a dose of 400 mg daily until progression or unacceptable toxicity, cisplatin was administered at dose 50 mg/m2 day 1 and 2, every 3 weeks. Twelve evaluable patients had to be enrolled into the first cohort, and if 0 of 12 patients had treatment response, the study was to be terminated. The results of the first stage of the trial are presented in the this report. Results: Median age was 36 years (range: 29 – 48 years). Median number of treatment cycles was 2 (range 1 – 6). During a median follow-up period of 3.1 months (range: 1.3 – 13.9), all (100%) patients experienced disease progression and died. None of patients achieved objective response to treatment, therefore the study was terminated in first stage. Median progression-free survival (PFS) was 1.4 months, 95% CI (0.7 – 1.5 months), and median overall survival (OS) was 2.9 months 95% CI (1.5 – 4.7 months). Disease stabilization for at least 6 months was observed in 2 (16.7%) patients. Treatment was well tolerated, however, 5 (41.7%) of patients experienced grade 3/4 fatigue, 4 (33.3%) thrombocytopenia, 3 (25.0%) anemia, while 2 (16.7%) experienced neutropenia, nausea and infection. Conclusions: This study failed to achieve its primary end point and our data suggest limited efficacy of disulfiram in restoring sensitivity to cisplatin in multiple relapsed/refractory germ cell tumors. Clinical trial information: NCT03950830.

Chemotherapy-triggered changes in stromal compartment drive tumor invasiveness and progression of breast cancer

Background

Chemotherapy remains a standard treatment option for breast cancer despite its toxic effects to normal tissues. However, the long-lasting effects of chemotherapy on non-malignant cells may influence tumor cell behavior and response to treatment. Here, we have analyzed the effects of doxorubicin (DOX) and paclitaxel (PAC), commonly used chemotherapeutic agents, on the survival and cellular functions of mesenchymal stromal cells (MSC), which comprise an important part of breast tumor microenvironment.

Methods

Chemotherapy-exposed MSC (DOX-MSC, PAC-MSC) were co-cultured with three breast cancer cell (BCC) lines differing in molecular characteristics to study chemotherapy-triggered changes in stromal compartment of the breast tissue and its relevance to tumor progression in vitro and in vivo. Conditioned media from co-cultured cells were used to determine the cytokine content. Mixture of BCC and exposed or unexposed MSC were subcutaneously injected into the immunodeficient SCID/Beige mice to analyze invasion into the surrounding tissue and possible metastases. The same mixtures of cells were applied on the chorioallantoic membrane to study angiogenic potential.

Results

Therapy-educated MSC differed in cytokine production compared to un-exposed MSC and influenced proliferation and secretory phenotype of tumor cells in co-culture. Histochemical tumor xenograft analysis revealed increased invasive potential of tumor cells co-injected with DOX-MSC or PAC-MSC and also the presence of nerve fiber infiltration in tumors. Chemotherapy-exposed MSC have also influenced angiogenic potential in the model of chorioallantoic membrane.

Conclusions

Data presented in this study suggest that neoadjuvant chemotherapy could possibly alter otherwise healthy stroma in breast tissue into a hostile tumor-promoting and metastasis favoring niche. Understanding of the tumor microenvironment and its complex net of signals brings us closer to the ability to recognize the mechanisms that prevent failure of standard therapy and accomplish the curative purpose.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-021-02087-2.

Molecular features and gene expression signature of metastatic colorectal cancer (Review)

Uncontrollable metastatic outgrowth process is the leading cause of mortality worldwide, even in the case of colorectal cancer. Colorectal cancer (CRC) accounts for approximately 10% of all annually diagnosed cancers and 50% of CRC patients will develop metastases in the course of disease. Most patients with metastatic CRC have incurable disease. Even if patients undergo resection of liver metastases, the 5‑year survival rate ranges from 25 to 58%. Next‑generation sequencing of tumour specimens from large colorectal cancer patient cohorts has led to major advances in elucidating the genomic landscape of these tumours and paired metastases. The expression profiles of primary CRC and their metastatic lesions at both the gene and pathway levels were compared and led to the selection of early driver genes responsible for carcinogenesis and metastasis‑specific genes that increased the metastatic process. The genetic, transcriptional and epigenetic alteration encoded by these genes and their combination influence many pivotal signalling pathways, enabling the dissemination and outgrowth in distant organs. Therapeutic regimens affecting several different active pathways may have important implications for therapeutic efficacy.

Napabucasin overcomes cisplatin resistance in ovarian germ cell tumor-derived cell line by inhibiting cancer stemness

Background

Cisplatin resistance of ovarian yolk sac tumors (oYST) is a clinical challenge due to dismal patient prognosis, even though the disease is extremely rare. We investigated potential association between cisplatin resistance and cancer stem cell (CSC) markers in chemoresistant oYST cells and targeting strategies to overcome resistance in oYST.

Methods

Chemoresistant cells were derived from chemosensitive human oYST cells by cultivation in cisplatin in vitro. Derivative cells were characterized by chemoresistance, functional assays, flow cytometry, gene expression and protein arrays focused on CSC markers. RNAseq, methylation and microRNA profiling were performed. Quail chorioallantoic membranes (CAM) with implanted oYST cells were used to analyze the micro-tumor extent and interconnection with the CAM. Tumorigenicity in vivo was determined on immunodeficient mouse model. Chemoresistant cells were treated by inhibitors intefering with the CSC properties to examine the chemosensitization to cisplatin.

Results

Long-term cisplatin exposure resulted in seven-fold higher IC₅₀ value in resistant cells, cross-resistance to oxaliplatin and carboplatin, and increased migratory capacity, invasiveness and tumorigenicity, associated with hypomethylation of differentially methylated genes/promotors. Resistant cells exhibited increased expression of prominin-1 (CD133), ATP binding cassette subfamily G member 2 (ABCG2), aldehyde dehydrogenase 3 isoform A1 (ALDH3A1), correlating with reduced gene and promoter methylation, as well as increased expression of ALDH1A3 and higher overall ALDH enzymatic activity, rendering them cross-resistant to DEAB, disulfiram and napabucasin. Salinomycin and tunicamycin were significantly more toxic to resistant cells. Pretreatment with napabucasin resensitized the cells to cisplatin and reduced their tumorigenicity in vivo.

Conclusions

The novel chemoresistant cells represent unique model of refractory oYST. CSC markers are associated with cisplatin resistance being possible targets in chemorefractory oYST.

Permanent Pro-Tumorigenic Shift in Adipose Tissue-Derived Mesenchymal Stromal Cells Induced by Breast Malignancy

During cancer progression, breast tumor cells interact with adjacent adipose tissue, which has been shown to be engaged in cancer aggressiveness. However, the tumor-directed changes in adipose tissue-resident stromal cells affected by the tumor–stroma communication are still poorly understood. The acquired changes might remain in the tissue even after tumor removal and may contribute to tumor relapse. We investigated functional properties (migratory capacity, expression and secretion profile) of mesenchymal stromal cells isolated from healthy (n = 9) and tumor-distant breast adipose tissue (n = 32). Cancer patient-derived mesenchymal stromal cells (MSCs) (MSC-CA) exhibited a significantly disarranged secretion profile and proliferation potential. Co-culture with MDA-MB-231, T47D and JIMT-1, representing different subtypes of breast cancer, was used to analyze the effect of MSCs on proliferation, invasion and tumorigenicity. The MSC-CA enhanced tumorigenicity and altered xenograft composition in immunodeficient mice. Histological analysis revealed collective cell invasion with a specific invasive front of EMT-positive tumor cells as well as invasion of cancer cells to the nerve-surrounding space. This study identifies that adipose tissue-derived mesenchymal stromal cells are primed and permanently altered by tumor presence in breast tissue and have the potential to increase tumor cell invasive ability through the activation of epithelial-to-mesenchymal transition in tumor cells.

Disulfiram Overcomes Cisplatin Resistance in Human Embryonal Carcinoma Cells

Cisplatin resistance in testicular germ cell tumors (TGCTs) is a clinical challenge. We investigated the underlying mechanisms associated with cancer stem cell (CSC) markers and modalities circumventing the chemoresistance. Chemoresistant models (designated as CisR) of human embryonal carcinoma cell lines NTERA-2 and NCCIT were derived and characterized using flow cytometry, gene expression, functional and protein arrays. Tumorigenicity was determined on immunodeficient mouse model. Disulfiram was used to examine chemosensitization of resistant cells. ALDH1A3 isoform expression was evaluated by immunohistochemistry in 216 patients' tissue samples. Chemoresistant cells were significantly more resistant to cisplatin, carboplatin and oxaliplatin compared to parental cells. NTERA-2 CisR cells exhibited altered morphology and increased tumorigenicity. High ALDH1A3 expression and increased ALDH activity were detected in both refractory cell lines. Disulfiram in combination with cisplatin showed synergy for NTERA-2 CisR and NCCIT CisR cells and inhibited growth of NTERA-2 CisR xenografts. Significantly higher ALDH1A3 expression was detected in TGCTs patients' tissue samples compared to normal testicular tissue. We characterized novel clinically relevant model of chemoresistant TGCTs, for the first time identified the ALDH1A3 as a therapeutic target in TGCTs and more importantly, showed that disulfiram represents a viable treatment option for refractory TGCTs.

Mesenchymal stromal cells producing TNFα lack inhibitory effect against A375 experimental lung metastases

Cell-based anticancer therapy using mesenchymal stromal cells (MSCs) engineered to express therapeutic genes has a potential to target the cancer cells in vivo. Metastatic dissemination of melanoma remains a serious problem in the treatment. In our previous work we used MSCs overexpressing gene for tumor necrosis factor α (TNFα; MSCs/TNFα), and we achieved inhibition of melanoma xenograft growth when engineered MCSs/TNFα were coinjected with tumor cells subcutaneously. The TNFα as a pleiotropic cytokine induces apoptosis of tumor cells, creates "tumor resistant" microenvironment, enhances immune response and can have tumor destructive capacity in selected tumor types, especially in tumors of mesodermal origin.In this study we investigated the possibility of intravenously administered MCSs/TNFα to inhibit metastatic spread of A375 melanoma cells in the lungs. We confirmed elevated expression of TNFα transgene in the lung tissue 20 days after MCSs/TNFα intravenous infusion. We also documented that constitutive expression of TNFα transgene is able to neutralize the supportive effect of MSCs on melanoma cells growth. Metastatic spread of A375 melanoma cells in the lung was inhibited approximately to 50% after MCSs/TNFα i.v. administration in comparison to control group with parental MSCs supporting tumor growth. In conclusion, engineered MCSs/TNFα administered intravenously did not demonstrate significant antitumor effect against experimental melanoma lung metastases in this model settings.

Recent advances in understanding tumor stroma-mediated chemoresistance in breast cancer

Although solid tumors comprise malignant cells, they also contain many different non-malignant cell types in their micro-environment. The cellular components of the tumor stroma consist of immune and endothelial cells combined with a heterogeneous population of stromal cells which include cancer-associated fibroblasts. The bi-directional interactions between tumor and stromal cells therefore substantially affect tumor cell biology.Herein, we discuss current available information on these interactions in breast cancer chemo-resistance. It is acknowledged that stromal cells extrinsically alter tumor cell drug responses with profound consequences for therapy efficiency, and it is therefore essential to understand the molecular mechanisms which contribute to these substantial alterations because they provide potential targets for improved cancer therapy. Although breast cancer patient survival has improved over the last decades, chemo-resistance still remains a significant obstacle to successful treatment.Appreciating the important experimental evidence of mesenchymal stromal cells and cancer-associated fibroblast involvement in breast cancer clinical practice can therefore have important therapeutic implications.

Global and gene specific DNA methylation in breast cancer cells was not affected during epithelial-to-mesenchymal transition in vitro

Epithelial-to-mesenchymal transition (EMT) significantly affects the risk of metastasising in breast cancer. Plasticity and reversibility of EMT suggest that epigenetic mechanisms could be the key drivers of these processes, but little is known about the dynamics of EMT-related epigenetic alterations. We hypothesised that EMT, mediated by autocrine and paracrine signals, will be accompanied by changes in DNA methylation profiles. Therefore, conditioned medium from adipose tissue-derived mesenchymal stromal cells was used for induction of EMT in human breast cancer SK-BR-3 cell line. EMT-related morphological alterations and changes in gene expression of EMT-associated markers were assessed. To reverse EMT, 20 nm size gold nanoparticles (AuNPs) synthesized by the citrate reduction method were applied. Finally, DNA methylation of LINE-1 sequences and promoter methylation of TIMP3, ADAM23 and BRMS1 genes were quantitatively evaluated by pyrosequencing. Despite the presence of EMT-associated morphological and gene expression changes in tumour cells, EMT induced by adipose tissue-derived mesenchymal stromal cells had almost no effect on LINE-1 and gene-specific DNA methylation patterns of TIMP3, ADAM23 and BRMS1 genes. Although treatment for 24, 48 or 72 hours with 20 nm AuNPs at a concentration of 3 µg/ml slightly decreased gene expression of EMT-associated markers in SK-BR-3 cells, it did not alter global or gene-specific DNA methylation. Our results suggest that changes in DNA methylation are not detectable in vitro in early phases of EMT. Previously published positive findings could represent rather the sustained presence of potent EMT-inducing signals or the synergistic effect of various epigenetic mechanisms. Treatment with AuNPs slightly attenuated EMT, and their therapeutic potential needs to be further investigated.

Lymphoma transformation of tumor infiltrating lymphocytes observed in testicular patient‑derived xenograft models

Testicular germ cell tumors (TGCTs) are highly sensitive to cisplatin‑based chemotherapy. Nevertheless, there are metastatic tumors that do not completely respond to front‑line chemotherapy. For these tumors, surgical resection of residual masses is necessary to achieve long‑term disease control. Resected tissues represent valuable clinical material, which may be used for the engraftment into immunocompromised mice to produce patient‑derived xenografts (PDXs). They typically maintain similarities to the parental tumors and therefore serve as more realistic preclinical models. Moreover, a correlation between PDX treatment outcomes and clinical response to chemotherapy has been previously described. The aim of the present study was to establish and characterize TGCT patient‑derived xenografts. These originated from retroperitoneal lymph node metastases infiltrated with TGCTs following previous cisplatin‑based chemotherapy, in order to analyze novel treatment options for cisplatin‑resistant testicular tumors. We generated two testicular patient‑derived xenograft models in SCID beige male mice. Immunohistochemical analyses demonstrated that histological characteristics of the primary tumor were not retained, and transformation into lymphoma, and eventually plasmocytoma, was observed. A potential explanation for the lymphoma transformation observed in PDXs may include tumor‑infiltrating lymphocytes (TILs) in xenografted samples of patients, which are transformed following engraftment into immunodeficient recipient mice. Based on these data, we indicated that lymphomagenesis prevention and terminal differentiation represent new challenges in the establishment of PDX models derived from patients with germ cell tumors.

Molecular Mechanisms of Cisplatin Chemoresistance and Its Circumventing in Testicular Germ Cell Tumors

PURPOSE OF REVIEW

Testicular germ cell tumors (TGCTs) represent the most common solid tumors affecting young men. Majority of TGCTs respond well to cisplatin-based chemotherapy. However, patients with refractory disease have limited treatment modalities associated with poor prognosis. Here, we discuss the main molecular mechanisms associated with acquired cisplatin resistance in TGCTs and how their understanding might help in the development of new approaches to tackle this clinically relevant problem. We also discuss recent data on the strategies of circumventing the cisplatin resistance from different tumor types potentially efficient also in TGCTs.

RECENT FINDINGS

Recent data regarding deregulation of various signaling pathways as well as genetic and epigenetic mechanisms in cisplatin-resistant TGCTs have contributed to understanding of the mechanisms related to the resistance to cisplatin-based chemotherapy in these tumors. Understanding of these mechanisms enabled explaining why majority but not all TGCTs patients are curable with cisplatin-based chemotherapy. Moreover, it could lead to the development of more effective treatment of refractory TGCTs and potentially other solid tumors resistant to platinum-based chemotherapy. This review provides additional insights into mechanisms associated with cisplatin resistance in TGCTs, which is a complex phenomenon, and there is a need for novel modalities to overcome it.

Genetically engineered mesenchymal stromal cells in cancer gene therapy

Based on our experimental data, we aimed to emphasise the perspectives of the use of mesenchymal stromal cells (MSC) in the cancer gene therapy. On the other hand, we would like to point out factors which should be taken into consideration at their clinical use. In this review we define MSC as unique targets for targeted therapy. We proved the efficacy of experimental therapeutic approach utilising enzymatic conversion of non-toxic prodrug into chemotherapeutic by engineered MSC, and we observed significant cytotoxic effect in many preclinical models including metastatic disease. Treatment was enabled by affinity of MSC to tumour tissue and subsequent delivery of therapeutic molecule into the tumour. We also observed decreased efficacy of cell-mediated gene therapy on chemoresistant tumour cells. Moreover MSC can exert a supportive effect on tumour cells as well as to decrease the efficacy of conventional treatment. Besides obvious unique benefits connected to the use of MSC we pointed also to possible risks associated with their clinical application (Ref. 24).

ALDH1A3 upregulation and spontaneous metastasis formation is associated with acquired chemoresistance in colorectal cancer cells

Background

Efficiency of colorectal carcinoma treatment by chemotherapy is diminished as the resistance develops over time in patients. The same holds true for 5-fluorouracil, the drug used in first line chemotherapy of colorectal carcinoma.

Methods

Chemoresistant derivative of HT-29 cells was prepared by long-term culturing in increasing concentration of 5-fluorouracil. Cells were characterized by viability assays, flow cytometry, gene expression arrays and kinetic imaging. Immunomagnetic separation was used for isolation of subpopulations positive for cancer stem cells-related surface markers. Aldehyde dehydrogenase expression was attenuated by siRNA. In vivo studies were performed on SCID/bg mice.

Results

The prepared chemoresistant cell line labeled as HT-29/EGFP/FUR is assigned with different morphology, decreased proliferation rate and 135-fold increased IC₅₀ value for 5-fluorouracil in comparison to parental counterparts HT-29/EGFP. The capability of chemoresistant cells to form tumor xenografts, when injected subcutaneously into SCID/bg mice, was strongly compromised, however, they formed distant metastases in mouse lungs spontaneously. Derived cells preserved their resistance in vitro and in vivo even without the 5-fluorouracil selection pressure. More importantly, they were resistant to cisplatin, oxaliplatin and cyclophosphamide exhibiting high cross-resistance along with alterations in expression of cancer-stem cell markers such as CD133, CD166, CD24, CD26, CXCR4, CD271 and CD274. We also detected increased aldehyde dehydrogenase (ALDH) activity associated with overexpression of specific ALDH isoform 1A3. Its inhibition by siRNA approach partially sensitized cells to various agents, thus linking for the first time the ALDH1A3 and chemoresistance in colorectal cancer.

Conclusion

Our study demonstrated that acquired chemoresistance goes along with metastatic and migratory phenotype and can be accompanied with increased activity of aldehyde dehydrogenase. We describe here the valuable model to study molecular link between resistance to chemotherapy and metastatic dissemination.

ALDH1A inhibition sensitizes colon cancer cells to chemotherapy

Background

Recent evidence in cancer research, developed the notion that malignant tumors consist of different subpopulations of cells, one of them, known as cancer stem cells, being attributed many important properties such as enhanced tumorigenicity, proliferation potential and profound multidrug resistance to chemotherapy. Several key stem cells markers were identified in colon cancer. In our study we focused on the aldehyde dehydrogenase type 1 (ALDH1) expression in colon cancer-derived cell lines HT-29/eGFP, HCT-116/eGFP and LS-180/eGFP, and its role in the chemoresistance and tumorigenic potential.

Methods

The effect of pharmacological inhibition of ALDH activity by diethylaminobenzaldehyde (DEAB) and also effect of molecular inhibition by specific siRNA was evaluated in vitro in cultures of human colorectal cell lines. The expression level of different isoenzymes of aldehyde dehydrogenase was determined using qPCR. Changes in cell biology were evaluated by expression analysis, western blot and apoptosis assay. The efficiency of cytotoxic treatment in the presence of different chemotherapeutic drugs was analyzed by fluorimetric assay. Tumorigenicity of cells with specific ALDH1A1 siRNA was tested in xenograft model in vivo.

Results

Treatment by DEAB partially sensitized the tested cell lines to chemotherapeutics. Subsequently the molecular inhibition of specific isoforms of ALDH by ALDH1A1 or ALDH1A3 siRNA led to sensitizing of cell lines HT-29/eGFP, HCT-116/eGFP to capecitabine and 5-FU. On the model of athymic mice we observed the effect of molecular inhibition of ALDH1A1 in HT-29/eGFP cells by siRNA. We observed inhibition of proliferation of subcutaneous xenografts in comparison to control cells.

Conclusion

This research, verifies the significance of the ALDH1A isoforms in multidrug resistance of human colorectal cancer cells and its potential as a cancer stem cell marker. This provides the basis for the development of new approaches regarding the treatment of patients with colorectal adenocarcinoma and potentially the treatment of other tumor malignancies.

Role of the HGF/c-MET tyrosine kinase inhibitors in metastasic melanoma

Metastatic disease in a cancer patient still remains a therapeutic challenge. Metastatic process involves many steps, during which malignant cells succeed to activate cellular pathways promoting survival in hostile environment, engraftment and growth at the distant site from the primary tumor. Melanoma is known for its high propensity to produce metastases even at the early stages of the disease. Here we summarize the most important molecular mechanisms which were associated with the melanoma metastasis. Then, we specifically focus on the signaling pathway mediated by hepatocyte growth factor (HGF) and its receptor c-Met, which play an important role during physiological processes and were been associated with tumorigenesis. We also focus on the effect of the small molecule inhibitors of the tyrosine kinase domain of the c-Met receptor and its effects on properties of melanoma cell. We summarize recent studies, which involved inhibition of the HGF/c-Met signaling in order to decrease melanoma growth and metastatic capacity.

Targeted antitumor therapy mediated by prodrug-activating mesenchymal stromal cells

Mesenchymal stromal cells (MSCs) were introduced as tumor-targeted vehicles suitable for delivery of the gene-directed enzyme/prodrug therapy more than 10 years ago. Over these years key properties of tumor cells and MSCs, which are crucial for the treatment efficiency, were examined; and there are some critical issues to be considered for the maximum antitumor effect. Moreover, engineered MSCs expressing enzymes capable of activating non-toxic prodrugs achieved long-term curative effect even in metastatic and hard-to-treat tumor types in pre-clinical scenario(s). These gene-modified MSCs are termed prodrug-activating MSCs throughout the text and represent promising approach for further clinical application. This review summarizes major determinants to be considered for the application of the prodrug-activating MSCs in antitumor therapy in order to maximize therapeutic efficiency.

Metastatic Ovarian Cancer Can Be Efficiently Treated by Genetically Modified Mesenchymal Stromal Cells

Due to late diagnosis, often recurrence, formation of metastases and resistance to commonly used chemotherapeutics human ovarian carcinoma represents a serious disease with high mortality. Adipose tissue-derived mesenchymal stromal cells (AT-MSC) can serve as vehicles for therapeutic genes and we engineered AT-MSC to express either Herpes simplex virus thymidine kinase (HSVtk-MSC), which phosphorylates ganciclovir (GCV) to its toxic metabolites or yeast fused cytosine deaminase::uracil phosphoribosyltransferase (CD::UPRT-MSC), which converts 5-fluorocytosine (5-FC) to highly toxic 5-fluorouracil (5-FU). Here, we reported different responses of cytotoxicity mediated by CD::UPRT-MSC/5-FC treatment on human ovarian carcinoma cell lines-SKOV-3 and A2780 used in adherent or three-dimensional (3D) cell culture and we proved high potential of 3D model to predict results in our in vivo experiments. Both tumor cell lines showed similarly high chemosensitivity to the used treatment in adherent culture, but 3D model revealed severe discrepancy-only 36% of SKOV-3 cells but even 90% of A2780 cells were eliminated. This result served as a prognostic marker-we were able to achieve significantly decreased tumor volumes of subcutaneous xenografts of A2780 cells in nude mice and we prolonged tumor-free survival in 33% of animals bearing highly metastatic ovarian carcinoma after CD::UPRT-MSC/5-FC treatment.

Tyrosine kinase inhibitor SU11274 increased tumorigenicity and enriched for melanoma-initiating cells by bioenergetic modulation

Background

Small molecule inhibitor of tyrosine kinase activity, compound SU11274, was reported to have antitumorigenic and antimetastatic effect in melanoma. In this study, we evaluated, whether similar effect could be achieved also in other melanoma cells including highly tumorigenic and hypermetastatic variant.

Methods

The effect of SU11274 was evaluated in adherent and non-adherent melanosphere cultures of human melanoma cells M14, M4Beu, A375 and EGFP-A375/Rel3. Tumorigenicity of SU11274-treated cells was tested by limiting dilution assay in xenograft model in vivo.

Results

Here we show that SU11274 enriched for melanoma-initiating cells in vivo. SU11274 substantially decreased number of cells in adherent and spheroid cultures, but increased their tumorigenic potential as determined by higher frequency of tumor-initiating cells in vivo. SU11274 treatment was not associated with any significant alteration in the expression of stem cell markers, but the inhibitor stimulated higher level of pluripotent markers. SU11274-treated melanoma cells exhibited higher ATP content and lactate release indicative of increased glycolysis. Our data suggest that the SU11274 altered bioenergetic state of the cells. Indeed, pharmacological intervention with a glycolytic inhibitor dichloroacetate significantly reduced SU11274-promoted increase in melanoma-initiating cells and decreased their tumorigenicity.

Conclusions

Our data suggest critical role of glycolysis regulation in melanoma-initiating cells. Moreover, these data unravel substantial plasticity of melanoma cells and their adoptive mechanisms, which result in ambivalent response to therapeutic targeting.

Cisplatin-induced mesenchymal stromal cells-mediated mechanism contributing to decreased antitumor effect in breast cancer cells

BACKGROUND

Cells of the tumor microenvironment are recognized as important determinants of the tumor biology. The adjacent non-malignant cells can regulate drug responses of the cancer cells by secreted paracrine factors and direct interactions with tumor cells.

RESULTS

Human mesenchymal stromal cells (MSC) actively contribute to tumor microenvironment. Here we focused on their response to chemotherapy as during the treatment these cells become affected. We have shown that the secretory phenotype and behavior of mesenchymal stromal cells influenced by cisplatin differs from the naïve MSC. MSC were more resistant to the concentrations of cisplatin, which was cytotoxic for tumor cells. They did not undergo apoptosis, but a part of MSC population underwent senescence. However, MSC pretreatment with cisplatin led to changes in phosphorylation profiles of many kinases and also increased secretion of IL-6 and IL-8 cytokines. These changes in cytokine and phosphorylation profile of MSC led to increased chemoresistance and stemness of breast cancer cells.

CONCLUSION

Taken together here we suggest that the exposure of the chemoresistant cells in the tumor microenvironment leads to substantial alterations and might lead to promotion of acquired microenvironment-mediated chemoresistance and stemness.

Quality of life after bowel resection for Crohn´s disease - first results

INTRODUCTION

Crohn´s disease (CD) highly affects a patient´s quality of life. The aim of the study was to find out the impact of surgery on the quality of life (QoL) in CD patients and factors affecting their postoperative QoL.

METHODS

90 patients with CD who underwent surgery (bowel resection) filled out an EORTC QLQ-CR29 questionnaire preoperatively and again after the surgical procedure.

RESULTS

77% of the patients experienced a positive change (p<0.001), 22% negative and 11% no change.

CONCLUSION

In this cohort, we proved that surgical treatment improves the overall QoL in patients with CD. To determine factors which affect postoperative QoL, more patients need to be enrolled in future studies.Key words: Crohn´s disease - quality of life - surgery - bowel resection - Czech cohort.

Combined enzyme/prodrug treatment by genetically engineered AT-MSC exerts synergy and inhibits growth of MDA-MB-231 induced lung metastases

Background

Metastatic spread of tumor cells remains a serious problem in cancer treatment. Gene-directed enzyme/prodrug therapy mediated by tumor-homing genetically engineered mesenchymal stromal cells (MSC) represents a promising therapeutic modality for elimination of disseminated cells. Efficacy of gene-directed enzyme/prodrug therapy can be improved by combination of individual systems. We aimed to define the combination effect of two systems of gene therapy mediated by MSC, and evaluate the ability of systemically administered genetically engineered mesenchymal stromal cells to inhibit the growth of experimental metastases derived from human breast adenocarcinoma cells MDA-MB-231/EGFP.

Methods

Human adipose tissue-derived mesenchymal stromal cells (AT-MSC) were retrovirally transduced with fusion yeast cytosine deaminase::uracil phosphoribosyltransferase (CD::UPRT) or with Herpes simplex virus thymidine kinase (HSVtk). Engineered MSC were cocultured with tumor cells in the presence of prodrugs 5-fluorocytosin (5-FC) and ganciclovir (GCV). Combination effect of these enzyme/prodrug approaches was calculated. SCID/bg mice bearing experimental lung metastases were treated with CD::UPRT-MSC, HSVtk-MSC or both in combination in the presence of respective prodrug(s). Treatment efficiency was evaluated by EGFP-positive cell detection by flow cytometry combined with real-time PCR quantification of human cells in mouse organs. Results were confirmed by histological and immunohistochemical examination.

Results

We demonstrated various extent of synergy depending on tested cell line and experimental setup. The strongest synergism was observed on breast cancer-derived cell line MDA-MB-231/EGFP. Systemic administration of CD::UPRT-MSC and HSVtk-MSC in combination with 5-FC and GCV inhibited growth of MDA-MB-231 induced lung metastases.

Conclusions

Combined gene-directed enzyme/prodrug therapy mediated by MSC exerted synergic cytotoxic effect and resulted in high therapeutic efficacy in vivo.

Electronic supplementary material

The online version of this article (doi:10.1186/s13046-015-0149-2) contains supplementary material, which is available to authorized users.

Tumor-driven Molecular Changes in Human Mesenchymal Stromal Cells

Mesenchymal stromal cells (MSC) exert either tumor-stimulatory or tumor-inhibitory effect. The outcome of the tumor-MSC interaction is dictated by the tumor-specific activating signals. We analyzed the alterations in MSC phenotype in response to stimulation by tumor-secreted paracrine factors. Paracrine factors from human melanoma A375 and glioblastoma 8MGBA cells were used for prolonged culture of MSC to produce derived cells designated DIFF(A)-MSC or DIFF(G)-MSC, respectively. Derived cells were analyzed for the specific surface markers, the expression pattern of MSC markers and fibroblast-specific proteins. Changes in the cell phenotype were evaluated using scratch wound assay and tube formation in vitro; and xenotransplant growth in vivo. Our data show induced expression of vascular endothelial growth factor 2, CD146, fibroblast-specific protein, vimentin and endosialin in DIFF(A)-MSC cells. This indicates their differentiation towards the cells with features of tumor-associated fibroblasts upon stimulation with melanoma-secreted cytokines. Paracrine stimulation in DIFF(G)-MSC led to up-regulation of the genes involved in the MSC differentiation. MSC-specific surface marker characteristics were preserved in derived DIFF(A)-MSC and DIFF(G)-MSC cells. However, we observed increased proportion of CD146 and GD2 (neural ganglioside) positive cells and decreased expression of marker NG2 in the MSC exposed to tumor-conditioned medium. Melanoma-CM increased MSC migration, glioblastoma-CM compromised angiogenic capacity of MSC in vitro and the protumorigenic effect in vivo. Our data directly compare the pleiotropic effects mediated by the malignant cells on the MSC. Secreted paracrine factors from melanoma or glioblastoma differently changed molecular traits in MSC, which explains the dual role of MSC in tumor growth.

In vivo 5FU-exposed human medullary thyroid carcinoma cells contain a chemoresistant CD133+ tumor-initiating cell subset

BACKGROUND

The hierarchical model of solid tumor proposes the existence of rare tumor cell subpopulations with stem-cell properties. The glycoprotein prominin-1 (CD133) represents one of the cancer stem-cell markers in several tumor types. The CD133+ cell subpopulation was shown to be enriched for tumor-initiating and highly chemoresistant cells in human cancer(s).

METHODS

We investigated whether CD133+ cells derived from human medullary thyroid carcinoma (MTC) possess tumor-initiating properties in vivo and exhibit differential responses to chemotherapeutic agents. We demonstrated that separated CD133+ cells from the human MTC cell line TT are enriched for tumor-initiating cells as demonstrated by tumor formation in vivo. Nevertheless, TT CD133+ cells do not exhibit increased chemoresistance in comparison to parental cells. However, when MTC xenotransplants were treated with the chemotherapeutic drug 5-fluorouracil (5FU) in vivo, CD133 expression increased in MTC cells.

RESULTS

This cell line, designated FTTiv isolated from the drug-exposed xenotransplants, exhibits a significantly different response to 5FU associated with the substantial change in the expression profile of genes involved in 5FU metabolism and drug resistance. Moreover, the CD133+ tumor-initiating subpopulation derived from these drug-exposed FTTiv cells is significantly more resistant to 5FU and retains the chemoresistant properties upon FTTiv culture propagation.

CONCLUSIONS

These data suggest that the chemoresistant phenotype and the CD133+ MTC subpopulation emerged in response to chemotherapy in vivo.

Altered features and increased chemosensitivity of human breast cancer cells mediated by adipose tissue-derived mesenchymal stromal cells

Background

Mesenchymal stromal cells (MSCs) represent heterogeneous cell population suitable for cell therapies in regenerative medicine. MSCs can also substantially affect tumor biology due to their ability to be recruited to the tumor stroma and interact with malignant cells via direct contacts and paracrine signaling. The aim of our study was to characterize molecular changes dictated by adipose tissue-derived mesenchymal stromal cells (AT-MSCs) and the effects on drug responses in human breast cancer cells SKBR3.

Methods

The tumor cells were either directly cocultured with AT-MSCs or exposed to MSCs-conditioned medium (MSC-CM). Changes in cell biology were evaluated by kinetic live cell imaging, fluorescent microscopy, scratch wound assay, expression analysis, cytokine secretion profiling, ATP-based viability and apoptosis assays. The efficiency of cytotoxic treatment in the presence of AT-MSCs or MSCs-CM was analyzed.

Results

The AT-MSCs altered tumor cell morphology, induced epithelial-to-mesenchymal transition, increased mammosphere formation, cell confluence and migration of SKBR3. These features were attributed to molecular changes induced by MSCs-secreted cytokines and chemokines in breast cancer cells. AT-MSCs significantly inhibited the proliferation of SKBR3 cells in direct cocultures which was shown to be dependent on the SDF-1α/CXCR4 signaling axis. MSC-CM-exposed SKBR3 or SKBR3 in direct coculture with AT-MSCs exhibited increased chemosensitivity and induction of apoptosis in response to doxorubicin and 5-fluorouracil.

Conclusions

Our work further highlights the multi-level nature of tumor-stromal cell interplay and demonstrates the capability of AT-MSCs and MSC-secreted factors to alter the anti-tumor drug responses.

Tumor microenvironment and the role of mesenchymal stromal cells

Solid tumors are generally composed of two major components: heterogeneous malignant cells and non-malignant stromal part. The latter comprises several types of non-malignant cells of mesenchymal, endothelial and immune origin and together with the extracellular matrix significantly affects the biological properties of the tumor. This minireview is focused on recent advances in the understanding the role of tumor stromal component and its particular cell types in the tumor behavior. It summarizes the impact of mesenchymal stromal cells and the ways of their potential contribution to the tumor biology. As their role in the tumor development and the effects on the tumor cells remain controversial, we review the recent experimental evidence regarding the crucial molecular factors which determine their role in the tumors.

KEYWORDS

tumor microenvironment, human mesenchymal stromal cells, paracrine interaction, malignant cells.

Local bystander effect induces dormancy in human medullary thyroid carcinoma model in vivo

The extent of local bystander effect induced by fusion yeast cytosine deaminase::uracil phosphoribosyltransferase (yCD) in combination with 5-fluorocytosine (5FC) was evaluated in xenogeneic model of human medullary thyroid carcinoma (MTC). This approach to gene-directed enzyme/prodrug therapy (GDEPT) induces strong bystander cytotoxicity. Effector yCD-TT mixed with target EGFP-TT cells in a ratio 2:9 could achieve significant tumor regression and 14-fold decrease in serum marker calcitonin upon 5FC administration. Histopathological analysis unraveled that antitumor effect resulted in tumor dormancy and proliferation arrest of remaining tumor cell clusters in vivo. yCD/5FC combination represents another GDEPT approach to achieve tumor growth control in MTC.

Interaction of human adipose tissue-derived mesenchymal stromal cells with breast cancer cells

Human adipose tissue was shown to be a very attractive source of mesenchymal stromal cells that have a wide scale of potential applications in reconstructive plastic surgery and regenerative medicine. However, these cells were described to have profound effects on biological behaviour of tumour cells. The aim of this study was to analyze the influence of adipose tissue-derived human mesenchymal stromal cells (AT-MSC) on the proliferation of breast cancer cells. We have tested proliferation of three different human breast cancer cell lines under the influence of AT-MSC derived soluble factors as well as in the direct cocultures. These data were supplemented with the expression analysis of cytokines and their cognate receptors on the target cells. We have observed stimulation of proliferation in breast cancer cells MDA-MB-361, T47D and EGFP-MCF7. AT-MSC were found to secrete wide scale of cytokines, chemokines and growth factors, thus we concluded that this pro-proliferative effect was a result of their synergistic action. These data bring out a need to evaluate whether primary breast tumour derived human cells would respond to these type of stimuli in a similar manner in order to exclude any potential clinical risk related to the application of human mesenchymal stromal cells under the context of patient with history of breast cancer malignancy.

FcγRIIIA receptor genotype does not influence an outcome in patients with follicular lymphoma treated with risk-adapted immunochemotherapy

Antibody (rituximab) dependent cellular cytotoxicity is a key mechanism in killing CD20+ lymphoma cells. FcγRIIIA-158 V/F gene polymorphism results in expression of 3 variants of the FcγRIIIA receptor (FcγRIIIA) on cytotoxic lymphocytes with different receptor affinity. We studied 102 patients with newly diagnosed FL to assess whether the FcγRIIIA genotype influences outcome in patients treated with risk-adapted immunochemotherapy. The median age was 52 years (31-84); 90% of the patients had advanced (III/IV) clinical stages. The Follicular Lymphoma International Prognostic Index (FLIPI) scores were as follows: low 18.9%, intermediate 33.7% and high 47.4%. The front-line treatment was stratified according to the commonly used risk factors (FLIPI, beta-2-microglobuline and serum-Tyrosine-Kinase levels, bulky disease) into 3 treatment groups: (1) patients with FLIPI 0-1 treated with (R)-CHOP (51%), (2) patients under 60 (65) years of age with intermediate-risk disease (FLIPI 2) indicated for an intensive protocol (ProMACE-CytaBOM or sequential chemotherapy) (21%), and (3) patients under 60 (65) years with high-risk disease (FLIPI ≥3) treated with intensive chemotherapy plus autologous stem cell transplantation (28%). Rituximab was added to front-line chemotherapy in 59% of the patients. Generally, complete remission (CR) or unconfirmed CR was achieved in 85% of the patients, 11% had partial remission and 4% stable disease. Molecular CR (CRm) was achieved in 67.4% of 86 evaluable patients. Overall survival (OS) at 5 years reached 84% (95% CI 0.74-0.93); event-free survival (EFS) at 5 years was 58% (95% CI 0.45-0.71). The frequencies of FcγRIIIA-158 gene polymorphisms V/V, V/F and F/F were 8%, 50% and 42%, respectively. The FLIPI score distribution was not different in F/F patients as compared to V/F+V/V carriers (chi-square, P=0.7). The treatment modalities (treatment arm or rituximab administration) had the same distribution in V/V+V/F vs F/F patients (chi-square, P=0.16 and P=0.62, respectively). The CRm rates were similar in both subgroups of V/V+V/F vs F/F patients (chi-square, P=0.92). Survival curves for OS and EFS were not significantly different when comparing the subgroups of V/V+V/F vs F/F patients (P=0.28 and P=0.57, respectively). We found no difference in the quality of treatment response or survival after front-line immunochemotherapy between FcγRIIIA subgroups. FcγRIIIA polymorphism have no influence on the outcome of patients treated with risk-adapted chemotherapy with or without rituximab.

Tumor cell behaviour modulation by mesenchymal stromal cells

Background

Human mesenchymal stromal cells (MSC) hold a promise for future cell-based therapies due to their immunomodulatory properties and/or secretory activity. Nevertheless non-neoplastic tumor compartment could also originate from MSC. We aimed to show whether multipotent MSC derived from human adipose tissue (AT-MSC) could create tumor cell-protective milieu and affect tumor cell behaviour in vitro and in vivo.

Results

Here we have demonstrated tumor-promoting effect of AT-MSC on human melanoma A375 cells. AT-MSC coinjection mediated abrogation of tumor latency and supported subcutaneous xenotransplant growth from very low melanoma cell doses. Tumor incidence was also significantly increased by AT-MSC-derived soluble factors. AT-MSC supported proliferation, suppressed apoptosis and modulated melanoma cell responses to cytotoxic drugs in vitro. Expression and multiplex cytokine assays confirmed synergistic increase in VEGF that contributed to the AT-MSC-mediated support of A375 xenotransplant growth. Production of G-CSF and other factors implicated in formation of supportive proinflammatory tumor cell microenvironment was also confirmed. SDF-1α/CXCR4 signalling contributed to tumor-promoting effect of systemic AT-MSC administration on A375 xenotransplants. However, no support was observed for human glioblastoma cells 8MGBA co-injected along with AT-MSC that did not sustain tumor xenotransplant growth in vivo. Tumor-inhibiting response could be attributed to the synergistic action of multiple cytokines produced by AT-MSC on glioblastoma cells.

Conclusions

Herein we provide experimental evidence for MSC-mediated protective effect on melanoma A375 cells under nutrient-limiting and hostile environmental conditions resulting from mutual crosstalk between neoplastic and non-malignant cells. This tumor-favouring effect was not observed for the glioblastoma cells 8MGBA. Collectively, our data further strengthen the need for unravelling mechanisms underlying MSC-mediated modulation of tumor behaviour for possible future MSC clinical use in the context of malignant disease.

Genotoxic damage of human adipose-tissue derived mesenchymal stem cells triggers their terminal differentiation

Human adipose tissue-derived mesenchymal (stromal) stem cells (AT-MSCs) and genetically modified to express cytosine deaminase:uracil phosphoribosyltransferase (CDy-AT-MSCs) were treated with hydrogen peroxide in order to induce DNA damage and subsequently evaluate their genetic stability by single cell gel electrophoresis. Both cells types (parental and transgene modified) did not differ in the sensitivity to DNA breaks induction. Potential tumorigenicity of AT-MSCs and CDy-AT-MSCs was tested by subcutaneous inoculation of cell suspension into flank of immunocompromised mice. Dose of 15x10(6) cells was not found to be tumorigenic in given experimental setup. AT-MSCs, CDy-AT-MSCs and MSCs isolated from human lipoma were treated with chemical carcinogen 4-nitroquinoline-1-oxide (4NQO) in attempts to transform them. Surviving cells after genotoxic stress were not transformed but underwent replicative senescence. Irreparable DNA damage caused triggered adipogenic terminal differentiation, rather than apoptosis induction in all kinds of cells tested.

Cytosine deaminase expressing human mesenchymal stem cells mediated tumour regression in melanoma bearing mice

BACKGROUND

Previously, we validated capability of human adipose tissue-derived mesenchymal stem cells (AT-MSC) to serve as cellular vehicles for gene-directed enzyme prodrug molecular chemotherapy. Yeast fusion cytosine deaminase : uracil phosphoribosyltransferase expressing AT-MSC (CD y-AT-MSC) combined with systemic 5-fluorocytosine (5FC) significantly inhibited growth of human colon cancer xenografts. We aimed to determine the cytotoxic efficiency to other tumour cells both in vitro and in vivo.

METHODS

CD y-AT-MSC/5FC-mediated proliferation inhibition against a panel of human tumour cells lines was evaluated in direct and indirect cocultures in vitro. Antitumour effect was tested on immunodeficient mouse model in vivo.

RESULTS

Although culture expansion of CD y-AT-MSC sensitized these cells to 5FC mediated suicide effect, expanded CD y-AT-MSC/5FC still exhibited strong bystander cytotoxic effect towards human melanoma, glioblastoma, colon, breast and bladder carcinoma in vitro. Most efficient inhibition (91%) was observed in melanoma A375 cell line when directly cocultured with 2% of therapeutic cells CD y-AT-MSC/5FC. The therapeutic paradigm of the CD y -AT-MSC/5FC system was further evaluated on melanoma A375 xenografts on nude mice in vivo. Complete regression in 89% of tumours was achieved when 20% CD y-AT-MSC/5FC were co-injected along with tumour cells. More importantly, systemic CD y-AT-MSC administration resulted in therapeutic cell homing into subcutaneous melanoma and mediated tumour growth inhibition.

CONCLUSIONS

CD y-AT-MSC capability of targeting subcutaneous melanoma offers a possibility to selectively produce cytotoxic agent in situ. Our data further demonstrate beneficial biological properties of AT-MSC as a cellular vehicle for enzyme/prodrug therapy approach to molecular chemotherapy.

RASSF1A elicits apoptosis through an MST2 pathway directing proapoptotic transcription by the p73 tumor suppressor protein

RASSF1A is a tumor suppressor gene that is epigenetically silenced in a wide variety of sporadic human malignancies. Expression of alternative RASSF1 isoforms cannot substitute for RASSF1A-promoted cell-cycle arrest and apoptosis. Apoptosis can be driven by either activating Bax or by activation of MST kinases. The Raf1 proto-oncogene binds to MST2, preventing its activation and proapoptotic signaling. Here we show that key steps in RASSF1A-induced apoptosis are the disruption of the inhibitory Raf1-MST2 complex by RASSF1A and the concomitant enhancement of MST2 interaction with its substrate, LATS1. Subsequently, RASSF1A-activated LATS1 phosphorylates and releases the transcriptional regulator YAP1, allowing YAP1 to translocate to the nucleus and associate with p73, resulting in transcription of the proapoptotic target gene puma. Our results describe an MST2-dependent effector pathway for RASSF1A proapoptotic signaling and indicate that silencing of RASSF1A in tumors removes a proapoptotic signal emanating from p73.

Adipose tissue-derived human mesenchymal stem cells mediated prodrug cancer gene therapy

Human adipose tissue-derived mesenchymal stem cells (AT-MSC) are considered to be a promising source of autologous stem cells in personalized cell-based therapies. Tumor tracking properties of MSC provide an attractive opportunity for targeted transgene delivery into the sites of tumor formation. In the present study, we addressed whether the suicide gene introduction into human AT-MSC could produce a tumor-specific prodrug converting cellular vehicle for targeted chemotherapy. We prepared yeast fusion cytosine deaminase::uracil phosphoribosyltransferase gene-expressing cells [cytosine deaminase (CD)-expressing AT-MSC (CD-AT-MSC)] by retrovirus transduction. We explored their therapeutic potential on a model of human colon cancer in the presence of prodrug 5-fluorocytosine (5-FC). Gene manipulation of human AT-MSC did not sensitize CD-AT-MSC to 5-FC, thus overcoming the inherent disadvantage of suicide effect on cellular vehicle. CD-AT-MSC in combination with 5-FC augmented the bystander effect and selective cytotoxicity on target tumor cells HT-29 in direct coculture in vitro. We confirmed directed migration ability of AT-MSC and CD-AT-MSC toward tumor cells HT-29 in vitro. Moreover, we achieved significant inhibition of s.c. tumor xenograft growth by s.c. or i.v. administered CD-AT-MSC in immunocompromised mice treated with 5-FC. We confirmed the ability of CD-AT-MSC to deliver the CD transgene to the site of tumor formation and mediate strong antitumor effect in vivo. Taken together, these data characterize MSC derived from adipose tissue as suitable delivery vehicles for prodrug converting gene and show their utility for a personalized cell-based targeted cancer gene therapy.

Endorectal sonography in rectal cancer staging and indication for local surgery

BACKGROUND/AIMS

Radical surgery still plays a decisive role in the therapy of rectal cancer. Besides classical abdominal operations, an alternative is transanal endoscopic resection of rectal tumor at T1 and T2 stages. Indication for local resection of malignant rectal tumor requires an accurate preoperative staging.

METHODOLOGY

The paper evaluates the accuracy of 3D endorectal sonography in rectal cancer staging. In the group of 78 patients the staging of preoperative 3D endorectal sonography was compared with a final histopathologic of the operative sample.

RESULTS

The results obtained indicate that the preoperative staging of malignant rectal tumor using 3D endorectal sonography represents 100% only in the pT1 stage. In the pT2 stage, the accuracy of 3D endorectal sonography is 72%, in pT3 and pT4 represents 92%.

CONCLUSIONS

On the basis of our experience, complicated interpretation of findings obtained by 3D endorectal sonography occurs at limits of T2-T3 and T3-T4. In these localizations the peripheral reactive fibrous and inflammatory sections in the vicinity of tumor tissue often involve even the next layer of rectal wall and leads to overevaluation of invasion depth at endorectal sonography of rectal cancer.

Raf-1 sets the threshold of Fas sensitivity by modulating Rok-alpha signaling

Ablation of the Raf-1 protein causes fetal liver apoptosis, embryonic lethality, and selective hypersensitivity to Fas-induced cell death. Furthermore, Raf-1–deficient cells show defective migration as a result of the deregulation of the Rho effector kinase Rok-α. In this study, we show that the kinase-independent modulation of Rok-α signaling is also the basis of the antiapoptotic function of Raf-1. Fas activation stimulates the formation of Raf-1–Rok-α complexes, and Rok-α signaling is up-regulated in Raf-1–deficient cells. This leads to increased clustering and membrane expression of Fas, which is rescued both by kinase-dead Raf-1 and by interfering with Rok-α or its substrate ezrin. Increased Fas clustering and membrane expression are also evident in the livers of Raf-1–deficient embryos, and genetically reducing Fas expression counteracts fetal liver apoptosis, embryonic lethality, and the apoptotic defects of embryonic fibroblasts. Thus, Raf-1 has an essential function in regulating Fas expression and setting the threshold of Fas sensitivity during embryonic life.

Long-term infection with retroviral structural gene vector provides protection against bovine leukemia virus disease in rabbits

Bovine leukemia virus (BLV) infection of rabbits is a tractable model system to evaluate vaccination strategies against lymphotropic retroviruses, which represent a global human health problem. We have previously developed genetically simplified BLV structural gene vector (SGV) that replicates BLV structural and enzymatic genes independently of BLV regulatory and accessory genes. Results of a 20-month study in a rabbit model demonstrated that BLV SGV induces an antiviral immunological response and lacks pathogenicity. Here, these chronically infected-BLV SGV rabbits are assessed in a proof-of-principle study of preventative vaccination against challenge with pathogenic BLV. This study commences 24 months after BLV SGV inoculation and proceeds for an additional 20 months. The previously characterized BLV SGV rabbits and age-matched control rabbits were challenged with 1 x 10(8) fetal lamb kidney/BLV producer cells. BLV SGV rabbits seroconverted upon BLV challenge, but did not progress to BLV infection nor clinical disease. By contrast, naive rabbits became infected and succumbed to lymphotropic disease. Our findings provide proof-of-principle that chronic infection with BLV SGV induces protection against BLV infection. The data indicate that SGV based on HTLV or HIV is a promising approach against lymphotropic disease by human retroviruses.

Embryonic lethality and fetal liver apoptosis in mice lacking the c-raf-1 gene

The Raf kinases play a key role in relaying signals elicited by mitogens or oncogenes. Here, we report that c-raf-1(-/-) embryos are growth retarded and die at midgestation with anomalies in the placenta and in the fetal liver. Although hepatoblast proliferation does not appear to be impaired, c-raf-1(-/-) fetal livers are hypocellular and contain numerous apoptotic cells. Similarly, the poor proliferation of Raf-1(-/-) fibroblasts and hematopoietic cells cultivated in vitro is due to an increase in the apoptotic index of these cultures rather than to a cell cycle defect. Furthermore, Raf-1- deficient fibroblasts are more sensitive than wild- type cells to specific apoptotic stimuli, such as actinomycin D or Fas activation, but not to tumor necrosis factor-alpha. MEK/ERK activation is normal in Raf-1-deficient cells and embryos, and is probably mediated by B-RAF. These results indicate that the essential function of Raf-1 is to counteract apoptosis rather than to promote proliferation, and that effectors distinct from the MEK/ERK cascade must mediate the anti-apoptotic function of Raf-1.

Bovine leukemia virus structural gene vectors are immunogenic and lack pathogenicity in a rabbit model

Infection with a replication-competent bovine leukemia virus structural gene vector (BLV SGV) is an innovative vaccination approach to prevent disease by complex retroviruses. Previously we developed BLV SGV that constitutively expresses BLV gag, pol, and env and related cis-acting sequences but lacks tax, rex, RIII, and GIV and most of the BLV long terminal repeat sequences, including the cis-acting Tax and Rex response elements. The novel SGV virus is replication competent and replicates a selectable vector to a titer similar to that of the parental BLV in cell culture. The overall goal of this study was to test the hypothesis that infection with BLV SGV is nonpathogenic in rabbits. BLV infection of rabbits by inoculation of cell-free BLV or cell-associated BLV typically causes an immunodeficiency-like syndrome and death by 1 year postinfection. We sought to evaluate whether in vivo transfection of BLV provirus recapitulates pathogenic BLV infection and to compare BLV and BLV SGV with respect to infection, immunogenicity, and clinical outcome. Three groups of rabbits were subjected to in vivo transfection with BLV, BLV SGV, or negative control DNA. The results of our 20-month study indicate that in vivo transfection of rabbits with BLV recapitulates the fatal BLV infection produced by cell-free or cell-associated BLV. The BLV-infected rabbits exhibited sudden onset of clinical decline and immunodeficiency-like symptoms that culminated in death. BLV and BLV SGV infected peripheral blood mononuclear cells and induced similar levels of seroconversion to BLV structural proteins. However, BLV SGV exhibited a reduced proviral load and did not trigger the immunodeficiency-like syndrome. These results are consistent with the hypothesis that BLV SGV is infectious and immunogenic and lacks BLV pathogenicity in rabbits, and they support the use of this modified proviral vector delivery system for vaccines against complex retroviruses like BLV.

DNA/genetic vaccination (minireview)

An important new approach to vaccination is plasmid DNA injection in vivo that can elicit an immune response against protein(s) encoded. Antigen that is expressed from the in vivo transfected cells induces both humoral and cellular immune response. DNA immunization is generally applicable for a wide range of proteins. It can provide an organism with immunity against viruses, bacteria, parasites, and tumors. DNA vaccines can overcome the disadvantages of vaccines presently used as well as provide various new vaccines that are currently not available. This minireview provides an overview of evaluated DNA vaccine candidates against infectious agents and certain cancers.

In vivo study of genetically simplified bovine leukemia virus derivatives that lack tax and rex

Genetically simplified derivatives of complex retroviruses that replicate in animal models are useful tools to study the role of the complex regulatory genes in virus infection and pathogenesis and were proposed as a novel approach toward the development of vaccines against complex retroviruses. Previously we developed genetically simple derivatives of bovine leukemia virus (BLV) that can replicate in tissue culture independently of the BLV regulatory proteins, Tax and Rex, and the RIII and GIV open reading frames (K. Boris-Lawrie and H. M. Temin, J. Virol. 69:1920-1924, 1995). These derivatives are encoded on novel, hybrid retrovirus genomes that contain transcriptional control sequences of a simple retrovirus and gag-pol or env genes of the complex BLV. The first-generation simple BLV derivatives replicate as complementary viruses (coviruses) by using separate gag-pol or env genomes, and therefore virus spread is limited to cells that are infected with both covirus genomes. Here we describe a second-generation simple BLV derivative that is encoded on a single hybrid genome. We show the virus to be replication competent by successive passage on D17 target cells and by analysis of viral RNA and proteins in the infected cells. Furthermore, we evaluate the immunogenicity and infectivity of the simple BLV derivatives in a BLV animal model. Small groups of rats were injected either with virus-producing cells or with proviral DNA. Western immunoblot analysis revealed that antibodies against the major viral antigenic determinants are induced in response to either method of introduction and that seroconversion is sustained in most of the rats for at least 6 months (the duration of the study). The magnitudes of the antiviral responses were similar in rats infected with the first-generation simple BLV coviruses, the second-generation replication-competent derivative, or wild-type BLV. Wild-type BLV typically infects peripheral blood mononuclear cells (PBMC), and the simple BLV derivatives were also found to infect PBMC as demonstrated by PCR amplification of proviral sequences and reverse transcriptase PCR amplification of viral RNA in treated rats. These results establish that simple BLV derivatives lacking tax and rex are infectious and immunogenic in rats. These viruses will be useful tools in comparative studies with BLV to evaluate the role of tax and rex in maintenance of virus load and in disease outcome.