Drug Sensitivity Of Tumor Cells Research Articles

Purinergic signalling in cancer therapeutic resistance: From mechanisms to targeting strategies.

Purinergic signalling, consisting of extracellular purines and purinergic receptors, modulates cell proliferation, invasion and immunological reaction during cancer progression. Here, we focus on current evidence that suggests the crucial role of purinergic signalling in mediating cancer therapeutic resistance, the major obstacle in cancer treatment. Mechanistically, purinergic signalling can modulate the tumor microenvironment (TME), epithelial-mesenchymal transition (EMT) and anti-tumor immunity, thus affecting drug sensitivity of tumor cells. Currently, some agents attempting to target purinergic signalling either in tumor cells or in tumor-associated immune cells are under preclinical or clinical investigation. Moreover, nano-based delivery technologies significantly improve the efficacy of agents targeting purinergic signalling. In this review article, we summarize the mechanisms of purinergic signalling in promoting cancer therapeutic resistance and discuss the potentials and challenges of targeting purinergic signalling in future cancer treatment.

Erxian Decoction Enhances the Tamoxifen Sensitivity in Luminal Breast Cancer through the PI3K‐AKT Signaling Pathway

AbstractBackground: The primary and secondary resistance of luminal breast cancer (LBC) against endocrine therapy is a serious clinical problem. At present, it has been confirmed that Erxian Decoction can improve the sensitivity of LBC to tamoxifen (TAM), but its mechanism is not clear. The purpose of this paper is to explore the molecular mechanism that causes Erxian Decoction to increase the sensitivity of LBC to TAM.Methods: The potential targets and related pathways of Erxian Decoction inhibiting LBC were screened through bioinformatics. The small molecular compounds that could stably bind to LBC targets were determined by molecular docking. The stable interaction of the target and the small molecular compounds was revealed by the cell thermal shift assay (CETSA). Cell Counting Kit‐8 (CCK‐8) was used to verify the effect of Erxian Decoction and TAM on the cell activity of LBC. Flow cytometry was used to verify the effect of Erxian Decoction and TAM on the apoptosis of LBC cells. Western blot was used to detect the expression of PI3K‐AKT pathway‐related proteins in cells.Results: ERBB2 was screened as a potential target for the treatment of LBC. Based on molecular docking and CETSA results, the stable interaction between luteolin and ERBB2 was confirmed. CCK‐8 results showed that luteolin could inhibit the cell activity of LBC, and luteolin treatment could improve the drug sensitivity of tumor cells to TAM. The results of flow cytometry showed that compared with TAM treatment alone, the addition of luteolin trefatment promoted the apoptosis level of LBC cells. Western blot results indicated that luteolin could inhibit the PI3K‐AKT signal pathway by combining with ERBB2.Conclusion: Luteolin in Erxian Decoction inhibited the progression of LBC and enhanced the sensitivity of LBC to TAM by binding with ERBB2 to down‐regulate the activity of the PI3K‐AKT signaling pathway. This study provided theoretical support for endocrine therapy of TAM‐resistant LBC patients.

Reconstructing Tumor Microenvironment Using Photoresponsive Cyanobacteria to Reversal Chemoresistance for Robust Chemotherapy

The solid tumor microenvironment (TME) plays a crucial role in tumor biological behavior, development, and chemoresistance. Herein, a promising strategy is reported to remodel the TME and combat chemoresistance by employing the photoresponsive cyanobacteria (Synechococcus 7942, Syne). Syne exhibits inherent motility and enhanced permeability and retention effects to penetrate deep into the tumor. Under a 660 nm laser irradiation, Syne keeps a controllable, continuous, and robust O2 production ability through photosynthesis to alleviate tumor hypoxia and reduce monocarboxylate transporter 4 (MCT4) expression and exerts a gentle photodynamic effect by generating reactive oxidative species (ROS) in situ. In addition, adequate O2 supplement and ROS can not only facilitate intracellular doxorubicin (DOX) accumulation but also increase the drug sensitivity of tumor cells by downregulating the expression of chemoresistance‐related genes (e.g., heat shock factor‐1, mutant P53, and P‐glycoprotein). Compared with free DOX treatment, photoresponsive Syne with laser irradiation facilitates the deep penetration and accumulation of DOX in the tumor. Importantly, this Syne‐boosted chemotherapy achieves 100% survival in mice and complete tumor ablation with no evident systemic toxicity over a span of 90 days. Overall, this study presents a new insight and strategy to overcome chemotherapeutic resistance and eliminate tumors.

Non-coding RNAs in EMT regulation: Association with tumor progression and therapy response

RNA molecules lacking capacity in protein translation, are known as non-coding RNAs (ncRNAs). Growth, differentiation and migration are influenced by ncRNAs in cells. The abnormal expression of ncRNAs contributes to development of diseases, especially cancer. On the other hand, EMT is a vital mechanism for cancer invasion and diffusion in body. In this manuscript, role of ncRNAs in EMT regulation and subsequent effect on cancer progression is investigated. The miRNAs regulate EMT by affecting signaling pathways including PI3K/Akt and PTEN to modulate cancer metastasis. Furthermore, miRNA and EMT interaction has close association with drug sensitivity of tumor cells. LncRNAs can affect EMT via targeting ZEB1/2, Twist and Snail among others and similarly, based on the impact on EMT, sensitivity of cancer cells to therapy increases or decreases. CircRNAs regulate both drug sensitivity and metastasis of cancers by affecting EMT mechanism. Noteworthy, circRNAs and lncRNAs are capable of sponging miRNAs in modulating EMT mechanism. Exosomes belong to extracellular vesicles with low size that can be secreted by cells in transferring genetic materials. The transfer of ncRNAs by exosomes is performed and they can also regulate EMT in cancer progression. Finally, ncRNAs regulating EMT mechanism are used for cancer diagnosis and prognosis.

Tailored protein-conjugated DNA nanoplatform for synergistic cancer therapy.

Multidrug resistance (MDR) to chemotherapeutic drugs and targeted drug delivery are recurring issues in clinical cancer treatment. Here, a multifunctional fusion protein-DNA conjugate was designed as a co-delivery vehicle for anticancer peptides and chemotherapeutic drugs to combat both drug-resistant and drug-sensitive tumor cells. The fusion protein was constructed by fusing a PsTag polypeptide, a matrix metalloproteinase 2 (MMP2)-degradable domain, and the mitochondria-targeted pro-apoptotic peptide KLAKLAKKLAKLAK. Doxorubicin was efficiently loaded into the fusion protein pre-conjugated dendrimer-like DNA nanostructure. With the incorporation of enhanced stability, tumor targeting, and controlled-release elements, the tailored nanostructure can selectively enter tumor cells and synergistically exert antitumor activity with no significant adverse effects. Thus, these protein-conjugated DNA nanocarriers could be a potential co-delivery system for protein/peptide and chemotherapeutic drugs delivery in synergistic cancer therapy.

350P Molecular profiling of tumor tissue and tumor-derived cell lines in patients with glioblastoma

Glioma grade IV (glioblastoma, GBM) is an aggressive central nervous system tumor, which demonstrates high heterogeneity and resistance to treatment. Patient-derived cell cultures (GBM-lines) were shown to be representative models for analyzing the drug sensitivity of tumor cells for a better choice of appropriate treatment. Our aim was to compare molecular profiles of the tumor and the established patient’s cell line to find out if the cell line preserved important biomarkers of the tumor.

Long-term survival of an ovarian cancer patient harboring a RAD51C missense mutation.

Mutations in homologous recombination (HR) genes predispose to cancer but also sensitize to chemotherapeutics. Although therapy can initially be effective, cancers frequently cease responding, leading to recurrence and poor prognosis. Here we identify a germline mutation in RAD51C, a critical HR factor and known tumor suppressor, in an ovarian cancer patient with exceptionally long, progression-free survival. The RAD51C–T132P mutation is in a highly conserved residue within the nucleotide-binding site and interferes with single-strand DNA binding of the RAD51 paralog complex RAD51B–RAD51C–RAD51D–XRCC2 and association with another RAD51 paralog XRCC3. These biochemical defects lead to highly defective HR and drug sensitivity in tumor cells, ascribing RAD51C–T132P as a deleterious mutation that was likely causal for tumor formation. Conversely, its position within a critical site suggests that it is refractory to secondary mutations that would restore RAD51C gene function and lead to therapy resistance. A need for a greater understanding of the relationship between mutation position and reversion potential of HR genes is underscored, as it may help predict the effectiveness of therapies in patients with HR-deficient cancers.

Drug responsiveness of leukemic cells detected in vitro at diagnosis correlates with therapy response and survival in patients with acute myeloid leukemia.

BackgroundAcute myeloid leukemia (AML) is the most common acute leukemia in adults, and chemotherapy remains the most commonly used treatment approach for this group of hematological disorders. Drug resistance is one of the predictors of unfavorable prognosis for leukemia patients.AimThe purpose of this study was to perform a retrospective analysis of the survival rate in AML patients according to age, tumor status, and chemotherapy regimen received and to analyze the therapy response of AML patients depending on the treatment received, initial responsiveness of tumor cells to chemotherapeutic drugs measured in vitro at diagnosis and expression of immunological markers.MethodsThe survival of AML patients (n = 127) was analyzed using the Kaplan‐Meier method. Drug sensitivity of tumor cells of AML patients (n = 37) and the expression of immunological markers were evaluated by the WST test and flow cytometry, respectively. Correlation analysis was performed using Spearman's rank order correlation coefficient.ResultsWe found the treatment regimen to be the defining factor in the patient survival rate. In addition, the initial responsiveness of tumor cells to chemotherapeutic drugs measured in vitro at diagnosis correlated with the therapy response of AML: patients with high tumor cell sensitivity to particular cytotoxic drugs demonstrated a good response to treatment including these drugs, and patients with initial resistance of tumor cells to a particular chemotherapeutic agents and received it according to the clinical protocols demonstrated a poor response to antitumor therapy. Correlations of drug resistance in leukemic cells with the expression of immature and aberrant immunophenotype markers as established unfavorable prognostic factors confirm our assumption.ConclusionThe evaluation of the responsiveness of tumor cells to chemotherapy in vitro at diagnosis can be a useful tool for predicting the response of leukemia patients to planned chemotherapy.

The Extracellular Matrix Influences Ovarian Carcinoma Cells' Sensitivity to Cisplatinum: A First Step towards Personalized Medicine.

The development of personalized therapies for ovarian carcinoma patients is still hampered by several limitations, mainly the difficulty of predicting patients’ responses to chemotherapy in tumor cells isolated from peritoneal fluids. The main reason for the low predictive power of in vitro assays is related to the modification of the cancer cells’ phenotype induced by the culture conditions, which results in changes to the activation state and drug sensitivity of tumor cells compared to their in vivo properties. We have defined the optimal culture conditions to set up a prognostic test to predict high-grade serous ovarian carcinoma (HGSOC) patients’ responses to platinum chemotherapy. We evaluated the effects of hyaluronic acid (HA) and fibronectin matrices and the contribution of freezing/thawing processes to the cell response to platinum-based treatment, collecting spheroids from the ascitic fluids of 13 patients with stage II or III HGSOC. Our findings indicated that an efficient model used to generate predictive data for in vivo sensitivity to platinum is culturing fresh spheroids on HA, avoiding the use of previously frozen primary tumor cells. The establishment of this easy, reproducible and standardized testing method can significantly contribute to an improvement in therapeutic effectiveness, thus bringing the prospect of personalized therapy closer for ovarian carcinoma patients.

Nicotinamide N-methyltransferase decreases 5-fluorouracil sensitivity in human esophageal squamous cell carcinoma through metabolic reprogramming and promoting the Warburg effect.

Esophageal squamous cell carcinoma (ESCC) is a common malignant tumor with poor prognosis. And different individuals respond to the same drug differently. Increasing evidence has confirmed that metabolism reprogramming was involved in the drug sensitivity of tumor cells. However, the potential molecular mechanism of 5-fluorouracil (5-FU) sensitivity remains to be elucidated in ESCC cells. In this study, we found that the 5-FU sensitivity of TE1 cells was lower than that of EC1 and Eca109 cells. Gas chromatography-mass spectrometry analysis results showed that nicotinate and nicotinamide metabolism and tricarboxylic acid cycle were significantly different in these three cell lines. Nicotinamide N-methyltransferase (NNMT), a key enzyme of nicotinate and nicotinamide metabolism, was significantly higher expressed in TE1 cells than that in EC1 and Eca109 cells. Therefore, the function of NNMT on 5-FU sensitivity was analyzed in vitro and in vivo. NNMT downregulation significantly increased 5-FU sensitivity in TE1 cells. Meanwhile, the glucose consumption and lactate production were decreased, and the expression of glycolysis-related enzymes hexokinase 2, lactate dehydrogenase A, and phosphoglycerate mutase 1 were downregulated in NNMT knockdown TE1 cells. Besides, overexpression of NNMT in EC1 and Eca109 cells caused the opposite effects. Moreover, when glycolysis was inhibited by 2-deoxyglucose, the roles of NNMT on 5-FU sensitivity was weakened. In vivo experiments showed that NNMT knockdown significantly increased the sensitivity of xenografts to 5-FU and suppressed the Warburg effect. Overall, these results demonstrated that NNMT decreases 5-FU sensitivity in human ESCC cells through promoting the Warburg effect, suggesting that NNMT may contribute to predict the treatment effects of the clinical chemotherapy in ESCC.

Microtubule-associated protein 2 knockdown sensitizes glioma cells to vincristine treatment.

Gliomas are the most common and lethal tumor of the central nervous system (CNS). At present, standard treatment involves chemotherapy and radiotherapy after surgery, but the prognosis for most gliomas remains poor due to tumor heterogeneity and drug resistance. Microtubule-associated protein 2 (MAP2), a microtubule-stabilizing protein, plays a critical role in many cellular processes and may correlate with the proliferation, apoptosis, and drug sensitivity of tumor cells, especially their sensitivity to microtubule-targeting drugs (MTDs). In this study, we investigated the role of MAP2 in gliomas and its relationship to the chemosensitivity of vincristine (VCR), an MTD commonly used in glioma chemotherapy. We downregulated MAP2 expression in glioma cells using RNA interference, observed the resultant changes in the biological characteristics of the cells, and tested their drug sensitivity to VCR by MTT assay. The results show downregulation of MAP2 in glioma cells significantly inhibited cell viability and migration, induced apoptosis, and increased sensitivity to VCR in vitro. Our findings suggest that MAP2 may be a useful molecular marker in MTD chemotherapy and a potential therapeutic target in gliomas.

Phenotype-related drug sensitivity analysis of single CTCs for medicine evaluation.

Due to the heterogeneous and variable drug sensitivity of tumor cells, real-time monitoring of a patient's drug response is desirable for implementing personalized and dynamic therapy. Although considerable efforts have been directed at drug screening in living cells, performing repeated drug sensitivity analysis using patient-derived primary tumor cells at the single-cell level remains challenging. Here, we present an efficient approach to assess phenotype-related drug sensitivity at the single-cell level using patient-derived circulating tumor cells (CTCs) based on a drug sensitivity microfluidic chip (DS-Chip). The DS-Chip consists of a drug gradient generator and parallel cell traps, achieving continuous single CTC capture, drug gradient distributions, drug stimulation, fluorescent probe labeling and three-color fluorescence imaging. Based on the established DS-Chip, we investigated the drug sensitivity of single cells by simultaneously monitoring epithelial–mesenchymal transition (EMT) biomarkers and apoptosis in living cells, and verified the correlation between EMT gradients and drug sensitivity. Using the new approach, we further tested the optimal drug response dose in individual CTCs isolated from 5 cancer patients through fluorescence analysis of EMT and apoptosis. The DS-Chip allows noninvasive and real-time measurements of the drug sensitivity of a patient's tumor cells during therapy. This developed approach has practical significance and can effectively guide drug selection and therapeutic evaluation for personalized medicine.

PB1696 EVALUATION OF TUMOR CELL SENSITIVITY TO DAUNORUBICIN USING WST1 TEST IN ACUTE MYELOBLASTIC LEUKEMIA PATIENTS

Background:In recent years the MTT test for the assessment of the sensitivity of tumor cells to cytotoxic drugs in leukemia patients were used. In present study, the possibility of the WST1 test as a screening method of drug sensitivity of tumor cells of leukemia patients using peripheral blood and bone marrow samples was evaluated.Aims:The aim of this work was to study the effectiveness of the WST1 test for the initial estimation of the sensitivity of tumor cells to daunorubicin in vitro and prediction of the treatment response of patients with acute myeloblastic leukemia.Methods:The study included 42 patients with acute myeloblastic leukemia (AML). The average age of the patients was 53.3 ± 12.7 years. Leukemia cells were obtained from peripheral blood and bone marrow of patients. The sensitivity of tumor cells of patients with AML to daunorubicin in vitro using the WST1 test was made prior to initiating of cytotoxic therapy. Confirmation of multidrug resistance by evaluation of MDR1 mRNA expression levels in tumor cells of AML patients was performed on bone marrow and/or peripheral blood samples using quantitative real‐time reverse transcription‐polymerase chain reaction (real‐time qPCR).In all patients, the diagnosis was confirmed by the study of myelogram, flow cytofluorimetry, immunocytochemistry, cytogenetic analysis, as well as standard laboratory and instrumental studies that are included in the standard examination of patients with leukemia. Based on immunopenotyping and cytogenetic analysis, each patient was assigned to a risk group and prognosis. The obtained results were compared with the clinical and hematological response of these patients to cytotoxic therapy, as well as with the MDR1 mRNA expression level.Also we evaluated the survival of leukemia patients depending on the sensitivity to daunorubicin and MDR1 mRNA expression levels in tumor cells of AML patients.All statistical analyses were done with computer software MS Excel, OriginPro 7.5, Statistica 10.0.Results:Regardless of the class of chemotherapeutic drugs administered to the patients, the survival rate was higher in the group of patients with high sensitivity to daunorubicin and low expression levels of the MDR1 mRNA in tumor cells. Patients received daunorubicin within the “7 + 3” regimen (7 days of cytarabine and 3 days of daunorubicin) showed a high correlations (r = 0.8, p <0.05) between the expression levels of MDR1 mRNA and sensitivity to daunorubicin, moderate correlations (r = 0.63, p < 0.05) between the response to chemotherapy and sensitivity to daunorubicin, and a moderate correlations between the prediction (r = 0.48, p < 0.05) and the risk group (r = 0.49, p < 0.05) and sensitivity to daunorubicin. It is important to note that a high correlations (r = 0.86, p < 0.05) was found between the expression levels of MDR1 mRNA and the response to therapy.Summary/Conclusion:The obtained data demonstrate that the WST1 test can be effectively used as a screening method for the initial assessment of the sensitivity of tumor cells to daunorubicin in vitro and prediction of the response to treatment of AML patients.

Effect of miR-506 on pirarubicin sensitivity and on mesenchymal to epithelial transition and DNA damage homologous recombination repair process in leiomyosarcoma.

e22503 Background: MicroRNAs has been shown to be involved in many processes of tumorigenesis. Furthermore, miR-506 has been confirmed to be related to the occurrence of epithelial to mesenchymal transition (EMT) and tumor chemoresistance. However, the role of miR-506 in leiomyosarcoma has not yet been reported. Methods: A retrospective review of the 61 Chinese patients diagnosed with soft tissue leiomyosarcoma from January 2000 to December 2012 was investigated. Patient survival trends were examined by Kaplan-Meier analysis and log-rank tests. In vitro experiments were used to determine the biological function and physiological mechanism of drug sensitivity of miR-506. Results: In Chinese leiomyosarcoma patient cohort, we detected a decreased expression of miR-506 in the tumor tissues than that in marginal normal tissues. Tissue microarray analysis detected and confirmed a novel mesenchymal to epithelial transition (MET) in soft tissue leiomyosarcoma, also this MET phenomena was correlated with survival. In vitro, miR-506 inhibited the proliferation, migration, and invasion of leiomyosarcoma cells by promoting the occurrence of MET. Furthermore, RAD51, RAD52, ATM and ATR, which are defined as DNA damage homologous recombination repair related proteins, were highly expressed and associated with worse overall survival of leiomyosarcoma patients. Through targeting MET and DNA damage homologous recombination repair related proteins, miR-506 promoted the sensitivity of leiomyosarcoma cells to Pirarubicin. Conclusions: The current study reveals a novel mechanism that miR-506 increases the drug sensitivity of tumor cells, which are probably in association with the MET and DNA damage homologous recombination repair process.

Clinical and Prognostic Significance of Cell Sensitivity to Chemotherapy Detected in vitro on Treatment Response and Survival of Leukemia Patients.

Multidrug resistance (MDR) is a major challenge in leukemia treatment. The objective of this study was to identity predictors of MDR to allow for rapid and economical assessment of the efficacy of planned antitumor therapy for leukemia patients. The study included 113 patients with acute and chronic leukemias. Prior to antitumor therapy, we measured the sensitivity of tumor cells of patients to the panel of chemotherapeutic drugs, together with MDR1 mRNA and P-glycoprotein (P-gp) expression as one of the mechanisms of MDR, and compared these data with the response to therapy. The scales for leukemia patients according to therapy response, drug sensitivity of tumor cells, MDR1 mRNA and P-gp levels, and the presence of unfavorable immunological and cytogenetic markers were introduced for subsequent correlation analysis. We show that the drug resistance of tumor cells of leukemia patients estimated in vitro at diagnosis correlates with a poor response to chemotherapy and is usually combined with aberrant and immature immunological markers, cytogenetic abnormalities, and a high expression of MDR1 mRNA and P-gp. All together, these factors indicate unfavorable prognosis and low survival of leukemia patients. Thus, the sensitivity of tumor cells to chemotherapeutic drugs measured in vitro at diagnosis may have prognostic value for individual types of leukemia.

Therapy-induced enrichment of cancer stem-like cells in solid human tumors: Where do we stand?

The development of local recurrence and metastatic disease, most probably attributable to the intrinsic or acquired resistance of tumor cells to standard therapy, still constitute the major clinical problem preventing the cure of cancer patients. Despite progress in the research of new therapeutic targets and compounds, resistant cells displaying stem-like properties seem to play a leading role in therapeutic failures and to be the culprit cells responsible for associated tumor recurrence. A whole new plethora of research studies suggest that drug-tolerant cancer stem cells may be induced by conventional cancer chemotherapeutics such as doxorubicin, cisplatinum and ionizing radiation. This phenotypic plasticity and transition from a differentiated to stem-like cell state associates with the activation of diverse stem cell self-renewal (e.g. Notch, Hedgehog, Wnt), drug efflux (e.g. ABC transporters) and survival-related pathways (e.g. TGF-β, ERK, AKT), which may confer resistance and treatment failures in solid tumors. Therefore, combined therapeutic strategies aiming to simultaneously target drug-sensitive tumor cells and their capacity of phenotypic switching may lead to survival benefits and meaningful disease remissions. This knowledge can be applicable to the clinic and contribute to better therapeutic outcomes and prevent tumor recurrence.

Cytotoxicity of doxorubicin-conjugated poly[N-(2-hydroxypropyl)methacrylamide]-modified γ-Fe2O3 nanoparticles towards human tumor cells.

Doxorubicin-conjugated magnetic nanoparticles containing hydrolyzable hydrazone bonds were developed using a non-toxic poly[N-(2-hydroxypropyl)methacrylamide] (PHPMA) coating, which ensured good colloidal stability in aqueous media and limited internalization by the cells, however, enabled adhesion to the cell surface. While the neat PHPMA-coated particles proved to be non-toxic, doxorubicin-conjugated particles exhibited enhanced cytotoxicity in both drug-sensitive and drug-resistant tumor cells compared to free doxorubicin. The newly developed doxorubicin-conjugated PHPMA-coated magnetic particles seem to be a promising magnetically targeted vehicle for anticancer drug delivery.

Synthesis and biological evaluation of novel larotaxel analogues

Taxoids are a class of successful drugs and have been successfully used in chemotherapy for a variety of cancer types. However, despite the hope and promises that these taxoids have engendered, their utility is hampered by some clinic limitations. Extensive structure-activity relationship (SAR) studies of toxoids have been performed in many different laboratories. Whereas, SAR studies that based on the new-generation toxoid, larotaxel, have not been reported yet. In view of the advantages in preclinical and clinical data of larotaxel over former toxoids, new taxoids that strategicly modified at the C3’/C3′-N and C2 positions of larotaxel were designed, semi-synthesized, and examined for their potency and efficacy in vitro. As a result, it has been shown that the majority of these larotaxel analogues are exceptionally potent against both drug-sensitive tumor cells and tumor cells with drug resistance arising from P-glycoprotein over expression. Further in vivo antitumor efficacies investigations revealed A2 might be a potent antitumor drug candidate for further preclinical evaluation.

Human cancer-associated fibroblasts enhance glutathione levels and antagonize drug-induced prostate cancer cell death

Drug resistance is a major problem in cancer therapy. A growing body of evidence demonstrates that the tumor microenvironment, including cancer-associated fibroblasts (CAFs), can modulate drug sensitivity in tumor cells. We examined the effect of primary human CAFs on p53 induction and cell viability in prostate cancer cells on treatment with chemotherapeutic drugs. Co-culture with prostate CAFs or CAF-conditioned medium attenuated DNA damage and the p53 response to chemotherapeutic drugs and enhanced prostate cancer cell survival. CAF-conditioned medium inhibited the accumulation of doxorubicin, but not taxol, in prostate cancer cells in a manner that was associated with increased cancer cell glutathione levels. A low molecular weight fraction (<3 kDa) of CAF-conditioned medium had the same effect. CAF-conditioned medium also inhibited induction of reactive oxygen species (ROS) in both doxorubicin- and taxol-treated cancer cells. Our findings suggest that CAFs can enhance drug resistance in cancer cells by inhibiting drug accumulation and counteracting drug-induced oxidative stress. This protective mechanism may represent a novel therapeutic target in cancer.

Contrasting roles of the ABCG2 Q141K variant in prostate cancer

ABCG2 is a membrane transport protein that effluxes growth-promoting molecules, such as folates and dihydrotestosterone, as well as chemotherapeutic agents. Therefore it is important to determine how variants of ABCG2 affect the transporter function in order to determine whether modified treatment regimens may be necessary for patients harboring ABCG2 variants. Previous studies have demonstrated an association between the ABCG2 Q141K variant and overall survival after a prostate cancer diagnosis. We report here that in patients with recurrent prostate cancer, those who carry the ABCG2 Q141K variant had a significantly shorter time to PSA recurrence post-prostatectomy than patients homozygous for wild-type ABCG2 (P=0.01). Transport studies showed that wild-type ABCG2 was able to efflux more folic acid than the Q141K variant (P<0.002), suggesting that retained tumoral folate contributes to the decreased time to PSA recurrence in the Q141K variant patients. In a seemingly conflicting study, it was previously reported that docetaxel-treated Q141K variant prostate cancer patients have a longer survival time. We found this may be due to less efficient docetaxel efflux in cells with the Q141K variant versus wild-type ABCG2. In human prostate cancer tissues, confocal microscopy revealed that all genotypes had a mixture of cytoplasmic and plasma membrane staining, with noticeably less staining in the two homozygous KK patients. In conclusion, the Q141K variant plays contrasting roles in prostate cancer: 1) by decreasing folate efflux, increased intracellular folate levels result in enhanced tumor cell proliferation and therefore time to recurrence decreases; and 2) in patients treated with docetaxel, by decreasing its efflux, intratumoral docetaxel levels and tumor cell drug sensitivity increase and therefore patient survival time increases. Taken together, these data suggest that a patient's ABCG2 genotype may be important when determining a personalized treatment plan.