◥Purpose: Defects in the homologous recombination (HR) repair pathway are of clinical interest due to sensitivity of HR-deficient cells to PARP inhibitors. We were interested in defining PARP vulnerability in patients with metastatic colorectal cancer (mCRC) carrying KRAS and BRAF mutations who display poor prognosis, have limited therapeutic options, and represent an unmet clinical need.Experimental Design: We tested colorectal cancer cell lines, patient-derived organoids (PDO), and patient-derived xenografts (PDX) enriched for KRAS and BRAF mutations for sensitivity to the PARP inhibitor olaparib, and the chemotherapeutic agents oxaliplatin and 5-fluorouracil (5-FU). Genomic profiles and DNA repair proficiency of colorectal cancer models were compared with pharmacologic response.Results: Thirteen of 99 (around 13%) colorectal cancer cell lines were highly sensitive to clinically active concentrations of olaparib and displayed functional deficiency in HR. Response to PARP blockade was positively correlated with sensitivity to oxaliplatin in colorectal cancer cell lines as well as patientderived organoids. Treatment of PDXs with olaparib impaired tumor growth and maintenance therapy with PARP blockade after initial oxaliplatin response delayed disease progression in mice.Conclusions: These results indicate that a colorectal cancer subset characterized by poor prognosis and limited therapeutic options is vulnerable to PARP inhibition and suggest that PDObased drug-screening assays can be used to identify patients with colorectal cancer likely to benefit from olaparib. As patients with mCRC almost invariably receive therapies based on oxaliplatin, "maintenance" treatment with PARP inhibitors warrants further clinical investigation.

Although the involvement of type 1 (IP3R1) and type 2 (IP3R2) inositol 1,4,5-trisphosphate receptors in apoptosis induction has been well documented in different cancer cells and tissues, the function of type 3 IP3R (IP3R3) is still elusive. Therefore, in this work we focused on the role of IP3R3 in tumor cells in vitro and in vivo. We determined increased expression of this receptor in clear cell renal cell carcinoma compared to matched unaffected part of the kidney from the same patient. Thus, we hypothesized about different functions of IP3R3 compared to IP3R1 and IP3R2 in tumor cells. Silencing of IP3R1 prevented apoptosis induction in colorectal cancer DLD1 cells, ovarian cancer A2780 cells, and clear cell renal cell carcinoma RCC4 cells, compared to apoptosis in cells treated with scrambled siRNA. As expected, silencing of IP3R3 and subsequent apoptosis induction resulted in increased levels of apoptosis in all these cells. Further, we prepared a DLD1/IP3R3_del cell line using CRISPR/Cas9 gene editing method. These cells were injected into nude mice and tumor's volume was compared with tumors induced by DLD1 cells. Lower volume of tumors originated from DLD1/IP3R3_del cells was observed after 12 days, compared to wild type DLD1 cells. Also, the migration of these cells was lesser compared to wild type DLD1 cells. Apoptosis under hypoxic conditions was more pronounced in DLD1/IP3R3_del cells than in DLD1 cells. These results clearly show that IP3R3 has proliferative and anti-apoptotic effect in tumor cells, on contrary to the pro-apoptotic effect of IP3R1.

BackgroundCells 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.ResultsHuman 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.ConclusionTaken 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.

Progress in the development of effective cancer treatments is limited by the availability of tumor models. For decades, established cancer cell lines represented the mainstay preclinical tumor model, but these tools have limitations, such as limited capacity to recapitulate inter-and intra-tumor heterogeneity, adaptation to grow in two-dimensional cultures and the lack of Research.

BackgroundEfficiency 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.MethodsChemoresistant 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.ResultsThe 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.ConclusionOur 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.

GJIC, expression of enzymes involved in drug metabolism and ABC transporters correlate with the response of tumour cells to treatment by MSC-expressing prodrug-converting genes.

BackgroundRecent 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.MethodsThe 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.ResultsTreatment 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.ConclusionThis 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.

BackgroundMetastatic 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.MethodsHuman 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.ResultsWe 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.ConclusionsCombined gene-directed enzyme/prodrug therapy mediated by MSC exerted synergic cytotoxic effect and resulted in high therapeutic efficacy in vivo.Electronic supplementary materialThe online version of this article (doi:10.1186/s13046-015-0149-2) contains supplementary material, which is available to authorized users.