Aldehyde dehydrogenase activity as a functional marker for lung cancer

Melatonin protects against ketorolac induced gastric mucosal toxic injuries through molecular mechanism associated with the modulation of Arylakylamine N-Acetyltransferase (AANAT) activity

Ketorolac tromethamine (KT), is a widely used non-steroidal anti-inflammatory drug (NSAID) for treating moderate to severe pain. However, the use of KT has been restricted due to its highly toxic attributes that lead to severe gastric ulceration and bleeding. The protective effects of exogenous melatonin (MT) has been reported in conditions associated with gastro-intestinal disorders. This study aims at exploring the role of gastric endogenous MT level and it's metabolizing enzyme AANAT, at the onset of ketorolac mediated toxicities in the gastric mucosa. Gastric mucosal damage was induced in experimental rats by oral administration of graded doses of KT, where 50 mg/kg b.w. of KT was observed to incur maximum gastric lesions. However, gastric damages were found to be protected in rats, pre-treated with 60 mg/kg b.w. of MT. Post-sacrifice, mean ulcer index, oxidative status, total melatonin levels and enzyme activities associated with MT biosynthesis and catabolism were estimated. The results reveal that KT decreases AANAT activity with a concomitant decline in endogenous MT level which cumulatively aggravates gastric toxicity. Moreover, exogenous MT administration has been found to be protective in ameliorating this ulcerogenic process in rats, challenged with KT. Biochemical and histo-pathological observations revealed the reduction in oxidative stress level and replenishment of depleted gastric MT levels in MT pre-treated animals, which might be the causative factors in conferring protection to the gastric tissues and residing mitochondria. The results revealed a correlation between depleted gastric MT level and ulcer formation, which unveiled a novel ulcerogenic mechanism. This may bring forth future therapeutic relevance for treating patients suffering from KT mediated acute gastric toxicities.

Tissue-specific cancer stem/progenitor cells: Therapeutic implications

Surgical resection, chemotherapy, and radiation are the standard therapeutic modalities for treating cancer. These approaches are intended to target the more mature and rapidly dividing cancer cells. However, they spare the relatively quiescent and intrinsically resistant cancer stem cells (CSCs) subpopulation residing within the tumor tissue. Thus, a temporary eradication is achieved and the tumor bulk tends to revert supported by CSCs' resistant features. Based on their unique expression profile, the identification, isolation, and selective targeting of CSCs hold great promise for challenging treatment failure and reducing the risk of cancer recurrence. Yet, targeting CSCs is limited mainly by the irrelevance of the utilized cancer models. A new era of targeted and personalized anti-cancer therapies has been developed with cancer patient-derived organoids (PDOs) as a tool for establishing pre-clinical tumor models. Herein, we discuss the updated and presently available tissue-specific CSC markers in five highly occurring solid tumors. Additionally, we highlight the advantage and relevance of the three-dimensional PDOs culture model as a platform for modeling cancer, evaluating the efficacy of CSC-based therapeutics, and predicting drug response in cancer patients.

Novel mucoadhesive celecoxib-loaded cubosomal sponges: Anticancer potential and regulation of myeloid-derived suppressor cells in oral squamous cell carcinoma

Oral squamous-cell carcinoma (OSCC) is a widespread health problem. Myeloid-derived suppressor cells (MDSCs) are major tumor microenvironment (TME) population that govern many carcinogenesis aspects by establishing immunosuppressive milieu favoring tumor aggressiveness and treatment resistance. Cyclooxygenase-2 (COX-2) regulates MDSCs activity, hence, COX-2-selective inhibition by celecoxib (CXB) showed good anticancer effect at relatively high doses with possible subsequent cardiovascular complications. Therefore, targeted CXB delivery to MDSCs may represent a promising OSCC treatment strategy. Novel mucoadhesive-cubosomal buccal sponges were prepared for MDSCs targeting and were evaluated for their in-vitro quality attributes, ex-vivo mucoadhesion using buccal chicken-mucosa. Optimally-selected formulation showed considerable uptake by CD33⁺/11b⁺MDSCs in human OSCC cell-line (SCC-4) when quantitatively analyzed by flow-cytometry and examined using confocal-laser microscope. Optimum formulations loaded with low CXB doses (12 mg) were promoted to in-vivo studies via local application, using 4-nitroquinoline-1-oxide-induced OSCC in rats, and compared to their corresponding CXB gels. SP16 revealed the highest ability to decrease MDSC activation, recruitment and TME-immunosuppression in the isolated tumors. Consequently, SP16 exerted the greatest capacity to reduce histologic tumor grade, the OSCC-specific serum tumor markers levels, cancer hallmarks and stemness markers. CXB-loaded cubosomal sponges preferentially target MDSCs with noticeable anticancer potential and may exemplify novel mucoadhesive nanocarriers for OSCC treatment.

Epigenetic Alterations of Repeated Relapses in Patient-matched Childhood Ependymomas

Recurrence is frequent in pediatric ependymoma (EPN). Our longitudinal integrated analysis of 30 patient-matched repeated relapses (3.67 ± 1.76 times) over 13 years (5.8 ± 3.8) reveals stable molecular subtypes (RELA and PFA) and convergent DNA methylation reprogramming during serial relapses accompanied by increased orthotopic patient derived xenograft (PDX) (13/27) formation in the late recurrences. A set of differentially methylated CpGs (DMCs) and DNA methylation regions (DMRs) are found to persist in primary and relapse tumors (potential driver DMCs) and are acquired exclusively in the relapses (potential booster DMCs). Integrating with RNAseq reveals differentially expressed genes regulated by potential driver DMRs (CACNA1H, SLC12A7, RARA in RELA and HSPB8, GMPR, ITGB4 in PFA) and potential booster DMRs (PLEKHG1 in RELA and NOTCH, EPHA2, SUFU, FOXJ1 in PFA tumors). DMCs predicators of relapse are also identified in the primary tumors. This study provides a high-resolution epigenetic roadmap of serial EPN relapses and 13 orthotopic PDX models to facilitate biological and preclinical studies.

Cancer Stem Cell Markers in Rhabdomyosarcoma in Children

(1) Background: The aim of the present study was to assess the cancer stem cell (CSC) markers CD24, CD44, CD133, and ALDH1A1 in rhabdomyosarcoma (RMS) in children and to define their prognostic role in this group of patients. (2) Methods: The study material was archival tissue specimens collected from 49 patients under 18 years of age and who had been diagnosed with RMS. Immunohistochemistry (IHC) was used to evaluate the expression of the selected CSC markers in the tumor tissue. Expression was evaluated using a semiquantitative IRS scale based on the one developed by Remmele and Stenger and was correlated with the clinical and pathomorphological parameters of prognostic importance in RMS. (3) Results: Expression of the selected CSC markers CD24, CD44, CD133, and ALDH1A1 was demonstrated in 83.7%, 55.1%, 81.6%, and 100% of the RMS patients, respectively. The expression of all of the assessed CSC markers was statistically significantly higher in the study group versus the control group. No significant correlation was found between the expression of the selected CSC markers and clinical and pathological prognostic factors that were analyzed. The expression of the CSC markers did not have a significant influence on RMS survival rates. (4) Conclusions: The results of the conducted study confirm the expression of selected CSC markers in rhabdomyosarcoma tissue in children. The study did not support the prognostic relevance of the expression of any of the assessed CSC markers. However, further studies are needed to fully understand the relevance of the selected CSC markers in RMS carcinogenesis.

Ex Vivo Irradiation of Lung Cancer Stem Cells Identifies the Lowest Therapeutic Dose Needed for Tumor Growth Arrest and Mass Reduction In Vivo

Radiotherapy represents a first-line treatment for many inoperable lung tumors. New technologies offer novel opportunities for the treatment of lung cancer with the administration of higher doses of radiation in smaller volumes. Because both therapeutic and toxic treatment effects are dose-dependent, it is important to identify a minimal dose protocol for each individual patient that maintains efficacy while decreasing toxicity. Cancer stem cells sustain tumor growth, promote metastatic dissemination, and may give rise to secondary resistance. The identification of effective protocols targeting these cells may improve disease-free survival of treated patients. In this work, we evaluated the existence of individual profiles of sensitivity to radiotherapy in patient-derived cancer stem cells (CSCs) using both in vitro and in vivo models. Both CSCs in vitro and mice implanted with CSCs were treated with radiotherapy at different dose intensities and rates. CSC response to different radiation doses greatly varied among patients. In vitro radiation sensitivity of CSCs corresponded to the therapeutic outcome in the corresponding mouse tumor model. On the other side, the dose administration rate did not affect the response. These findings suggest that in vitro evaluation of CSCs may potentially predict patients’ response, thus guiding clinical decision.

A prodrug strategy for the in vivo imaging of aldehyde dehydrogenase activity

Therapy resistance is one of the biggest challenges facing clinical oncology. Despite a revolution in new anti-cancer drugs targeting multiple components of the tumour microenvironment, acquired or innate resistance frequently blunts the efficacy of these treatments. Non-invasive identification of drug-resistant tumours will enable modification of the patient treatment pathway through the selection of appropriate second-line treatments. Here, we have designed a prodrug radiotracer for the non-invasive imaging of aldehyde dehydrogenase 1A1 (ALDH1A1) activity. Elevated ALDH1A1 activity is a marker of drug-resistant cancer cells, modelled here with matched cisplatin-sensitive and -resistant human SKOV3 ovarian cancer cells. The aromatic aldehyde of our prodrug radiotracer was intracellularly liberated by esterase cleavage of the geminal diacetate and specifically trapped by ALDH through its conversion to the charged carboxylic acid. Through this mechanism of action, ALDH-specific retention of our prodrug radiotracer in the drug-resistant tumour cells was twice as high as the drug-sensitive cells. Acylal masking of the aldehyde afforded a modest protection from oxidation in the blood, which was substantially improved in carrier-added experiments. In vivo positron emission tomography imaging of tumour-bearing mice produced high tumour-to-background images and radiotracer uptake in high ALDH-expressing organs but was unable to differentiate between drug-sensitive and drug-resistant tumours. Alternative strategies to protect the labile aldehyde are currently under investigation.

Impact of Cancer Stem Cells and Cancer Stem Cell-Driven Drug Resiliency in Lung Tumor: Options in Sight

Causing a high mortality rate worldwide, lung cancer remains an incurable malignancy resistant to conventional therapy. Despite the discovery of specific molecular targets and new treatment strategies, there remains a pressing need to develop more efficient therapy to further improve the management of this disease. Cancer stem cells (CSCs) are considered the root of sustained tumor growth. This consensus corroborates the CSC model asserting that a distinct subpopulation of malignant cells within a tumor drives and maintains tumor progression with high heterogeneity. Besides being highly tumorigenic, CSCs are highly refractory to standard drugs; therefore, cancer treatment should be focused on eliminating these cells. Herein, we present the current knowledge of the existence of CSCs, CSC-associated mechanisms of chemoresistance, the ability of CSCs to evade immune surveillance, and potential CSC inhibitors in lung cancer, to provide a wider insight to drive a more efficient elimination of this pro-oncogenic and treatment-resistant cell fraction.

Tailored Quinolines Demonstrate Flexibility to Exert Antitumor Effects through Varied Mechanisms-A Medicinal Perspective

BACKGROUND

Quinoline is considered to be a privileged heterocyclic ring owing to its presence in diverse scaffolds endowed with promising activity profiles. In particular, quinoline containing compounds have exhibited substantial antiproliferative effects through the diverse mechanism of actions, which indicates that the heteroaryl unit is flexible as well as accessible to subtle structural changes that enable its inclusion in chemically distinct anti-tumor constructs.

METHODS

Herein, we describe a medicinal chemistry perspective on quinolines as anticancer agents by digging into the peer-reviewed literature as well as patents published in the past few years.

RESULTS

This review will serve as a guiding tool for medicinal chemists and chemical biologists to gain insights about the benefits of quinoline ring installation to tune the chemical architectures for inducing potent anticancer effects.

CONCLUSION

Quinoline ring containing anticancer agents presents enough optimism and promise in the field of drug discovery to motivate the researchers towards the continued explorations on such scaffolds. It is highly likely that adequate efforts in this direction might yield some potential cancer therapeutics in the future.

Radiosensitivity of Cancer Stem Cells Has Potential Predictive Value for Individual Responses to Radiotherapy in Locally Advanced Rectal Cancer

Simple Summary

Radiotherapy is often used as a neo-adjuvant treatment in locally advanced rectal cancer. While treatment generally induces an improvement in the outcome, some patients show resistance to treatment for reasons that still have to be elucidated. In this work, we report an in vitro and in vivo model based on patient-derived cancer stem cells. This model is able to predict individual responses to radiotherapy. The results indicate that cells found to be radiation-sensitive in vitro generated radiation-sensitive tumor xenografts upon subcutaneous implantation. Analogously, cancer stem cells (CSCs) that did not respond to in vitro radiation treatment generated radiation-resistant tumor xenografts. Moreover, radioresistant CSCs were generally isolated via biopsies of patients with poor responses to neo-adjuvant radiotherapy. This suggests that a cell-based in vitro test may itself be sufficient to predict outcomes in donor patients.

Abstract

Neo-adjuvant radiotherapy is frequently employed in the therapeutic management of locally advanced rectal cancer (LARC). Radiotherapy can both reduce local recurrence and improve the success of surgical procedures by reducing tumor mass size. However, some patients show a poor response to treatment, which results in primary resistance or relapse after apparent curative surgery. In this work, we report in vitro and in vivo models based on patient-derived cancer stem cells (CSCs); these models are able to predict individual responses to radiotherapy in LARC. CSCs isolated from colorectal cancer biopsies were subjected to in vitro irradiation with the same clinical protocol used for LARC patients. Animal models, generated by CSC xenotransplantation, were also obtained and treated with the same radiotherapy protocol. The results indicate that CSCs isolated from rectal cancer needle biopsies possess an intrinsic grade of sensitivity to treatment, which is also maintained in the animal model. Notably, the specific CSCs’ in vitro and in vivo sensitivity values correspond to patients’ responses to radiotherapy. This evidence suggests that an in vitro radiotherapy response predictivity assay could support clinical decisions for the management of LARC patients, thus avoiding radiation toxicity to resistant patients and reducing the treatment costs.

Differential Expression of TOM34, AL1A1, PADI2 and KLRBA in NNK Induced Lung Cancer in Wistar Rats and their Implications

BACKGROUND

Lung cancer is the most common cancer with a high mortality rate. The diagnosis only at advanced stages and lack of effective treatment are the main factors responsible for high mortality. Tobacco smoke is the major responsible factor for inflammation and tumor development in lungs.

OBJECTIVE

The present study was carried out to identify differentially expressed proteins and elucidate their role in carcinogenesis.

METHODS

The lung cancer was developed in Wistar rats by using NNK as carcinogen and cancer development was confirmed by histopathological examination. The 2D SDS PAGE was used to analyse total proteins and find out differentially expressed proteins in NNK treated lung tissue vis-a-vis control tissue. The findings of proteomic analysis were further validated by quantification of corresponding transcripts using Real Time PCR. Finally, Cytoscape was used to find out protein-protein interaction.

RESULTS

The histopathological examinations showed neoplasia at 9th month after NNK treatment. The proteomic analysis revealed several differentially expressed proteins, four of which were selected for further studies. (TOM34, AL1A1, PADI2 and KLRBA) that were up regulated in NNK treated lung tissue. The real time analysis showed over expression of the genes coding for the selected proteins. Thus, the proteomic and transcriptomic data corroborate each other. Further, these proteins showed interaction with the members of NF-κB family and STAT3.

CONCLUSION

We conclude that these proteins play a substantial role in the induction of lung cancer through NF-κB and STAT3 pathway. Therefore, these may have the potential to be used as therapeutic targets and for early detection of lung cancer.

Characterization of sphere cells derived from a patient-derived xenograft model of lung adenocarcinoma treated with ionizing radiation

PURPOSE

Cancer stem cells (CSCs) are relatively resistant to radiation compared to their non-tumorigenic progeny. Ionizing radiation (IR) can expand the pool of CSCs that leads to more aggressive cancers, but the reason underlying CSC-induced cancer aggressiveness after radiation therapy remains unclear. To understand this, we investigated the phenotypic and molecular characteristics of sphere cells formed from IR-treated patient-derived xenograft (PDX) lung adenocarcinoma tumors.

MATERIALS AND METHODS

After treatment with various modes of IR, we collected tumors from PDX mice and successfully obtained sphere cells. To compare tumorigenicity, we performed migration, invasion, and mouse transplantation assays with sphere cells from each group. To investigate the molecular features, we used a cDNA microarray and compared gene expression among groups.

RESULTS AND CONCLUSIONS

Tumorigenicity assays revealed that sphere cells from 2- or 5-Gy IR-treated tumors more aggressive than sphere cells from non-IR treated tumors. Microarray results showed that SERPIB4 and CCL2 were upregulated in sphere cells from IR-treated tumors compared to that in sphere cells from non-IR treated tumors. Interestingly, these genes are related to immune reactions in cancer. Taken together, our results suggest that the aggressiveness of sphere cells obtained after IR treatment is related to resistance, and provide new opportunities for exploring targeted therapies to overcome common radioresistance.

Albumin Nanoparticle of Paclitaxel (Abraxane) Decreases while Taxol Increases Breast Cancer Stem Cells in Treatment of Triple Negative Breast Cancer

Triple-negative breast cancer (TNBC) has a high rate of metastasis, which is associated with breast cancer stem-like cells (CSCs). Although Taxol (micelle formulation of paclitaxel) is the first line chemotherapy to treat TNBC, it increases CSCs in residual tumors. Abraxane, albumin nanoparticle of paclitaxel, showed lower plasma concentration compared to Taxol in both human and animal models, but it is not clear why Abraxane showed superior efficacy to Taxol in treatment of metastatic breast cancer in humans. In this study, we intend to investigate if Abraxane eliminates CSCs for its better efficacy. The results showed that Abraxane showed similar cytotoxicity in SUM149 cells in comparison with Taxol. Although Abraxane showed 3- to 5-fold lower blood drug concentration compared to Taxol, it achieved similar tumor drug concentration and 10-fold higher tumor/plasma ratio in SUM149 xenograft NOD/SCID mouse model. In addition, Abraxane and Taxol showed similar efficacy to shrink the tumor size in orthotopic breast cancer NOD/SCID mouse model. However, Abraxane decreased breast CSCs frequency by 3- to 9-fold, while Taxol increased breast CSCs frequency in an orthotopic breast cancer NOD/SCID mouse model. Furthermore, Abraxane increased 3- to 15-fold intracellular uptake in both ALDH+ CSCs and differentiated ALDH- cells in comparison with Taxol, which provides a mechanism for Abraxane's superior efficacy to eliminate CSCs in comparison with Taxol. Our data suggest albumin nanoparticle Abraxane may have a broad implication to enhance drug's efficacy by eliminating breast cancer stem cells for treatment of metastatic diseases.

Disulfiram potentiates the anticancer effect of cisplatin in atypical teratoid/rhabdoid tumors (AT/RT)

Atypical teratoid/rhabdoid tumor (AT/RT) is the most malignant tumor of the central nervous system that generally occurs in young children. Despite the use of intensive multimodal therapy for AT/RT, the prognosis is still poor. The brain tumor initiating cells in AT/RT cells has been suggested as one of the challenges in AT/RT treatment. These cells have high expression of aldehyde dehydrogenase (ALDH). We investigated the combination effect of the ALDH inhibitor, disulfiram and cisplatin in the treatment of AT/RT cells. Isobologram analysis revealed that the combination therapy synergistically increases AT/RT cell death. The enzyme activity of ALDH AT/RT cells was effectively reduced by the combination therapy. We proposed that the synergistic augmentation occurs, at least partially through an increase in cleaved Poly (ADP-ribose) polymerase (PARP)-dependent apoptosis mediated by activating transcription factor 3 (ATF3). In the AT/RT mouse model, the combination therapy decreased tumor volume and prolonged survival. Immunofluorescence assay in mouse brain tissues were consistent with the expression of ATF3 and cleaved PARP. Our study demonstrates enhanced anti-cancer effect of combination therapy of disulfiram and cisplatin. This combination might provide a viable therapeutic strategy for AT/RT patients.

Immunotherapy: Newer Therapeutic Armamentarium against Cancer Stem Cells

Mounting evidence from the literature suggests the existence of a subpopulation of cancer stem cells (CSCs) in almost all types of human cancers. These CSCs possessing a self-renewal capacity inhabit primary tumors and are more defiant to standard antimitotic and molecularly targeted therapies which are used for eliminating actively proliferating and differentiated cancer cells. Clinical relevance of CSCs emerges from the fact that they are the root cause of therapy resistance, relapse, and metastasis. Earlier, surgery, chemotherapy, and radiotherapy were established as cancer treatment modalities, but recently, immunotherapy is also gaining importance in the management of various cancer patients, mostly those of the advanced stage. This review abridges potential off-target effects of inhibiting CSC self-renewal pathways on immune cells and some recent immunological studies specifically targeting CSCs on the basis of their antigen expression profile, even though molecular markers or antigens that have been described till date as expressed by cancer stem cells are not specifically expressed by these cells which is a major limitation to target CSCs. We propose that owing to CSC stemness property to mediate immunotherapy response, we can apply a combination therapy approach by targeting CSCs and tumor microenvironment (TME) along with conventional treatment strategies as an effective means to eradicate cancer cells.

Paclitaxel-encapsulated core–shell nanoparticle of cetyl alcohol for active targeted delivery through oral route

Aim: Paclitaxel (PTX) has no clinically available oral formulations. Cetyl alcohol is metabolized by alcohol dehydrogenase and aldehyde dehydrogenase that are overexpressed in cancer cells. So, PTX-encapsulated core–shell nanoparticle of cetyl alcohol (PaxSLN) could target the cancer cells through oral route. Materials & methods: PaxSLN was synthesized using microemulsion template. Efficiency of PaxSLN was evaluated by ALDEFLUOR™, multicellular tumor spheroid formation inhibition assays and CT26 colorectal carcinoma animal model. Pharmacokinetics and biodistribution studies were done in Sprague Dawley rats. Results: PTX was encapsulated at the core of approximately 78 nm PaxSLN. PaxSLN targeted aldehyde dehydrogenase overexpressing cells. Its oral bioavailability was approximately 95% and chemotherapeutic efficacy was better than Taxol® and nab-PTX. Conclusion: A novel oral nanoformulation of PTX was developed.

GASC1 Promotes Stemness of Esophageal Squamous Cell Carcinoma via NOTCH1 Promoter Demethylation

The highest incidence of esophageal squamous cell carcinoma (ESCC) occurs in China. Cancer stem cells play key roles for tumor progression. Gene amplified in squamous cell carcinoma 1 (GASC1) is essential to maintain self-renewal and differentiation potential of embryonic stem cells. This study aimed to reveal the effect and mechanism of GASC1 on ESCC stemness. The biological function of GASC1 in ESCC was evaluated both in vitro and in vivo. ChIP assay was performed to determine the molecular mechanism of GASC1 in epigenetic regulation of NOTCH1. We found that GASC1 expression was increased in poor differentiated ESCC cells and tissues. ESCC patients with a high level of GASC1 presented a significantly worse survival rate. GASC1 expression in purified ALDH⁺ ESCC cells was significantly higher than that in ALDH⁻ cells. The stemness of ESCC was dramatically decreased after GASC1 blockade. Furthermore, blockade of GASC1 decreased NOTCH1 expression via increase of NOTCH1 promoter H3K9me2 and H3K9me3. Moreover, the impaired stemness after blockade of GASC1 could be reversed after transfection of NOTCH1 overexpression lentiviral vector. GASC1 promoted stemness in ESCC cells via NOTCH1 promoter demethylation. Therefore, GASC1/NOTCH1 signaling might be a potential therapeutic target for the treatment of ESCC patients.

Cancer cells stemness: A doorstep to targeted therapy

Recent advances in research on cancer have led to understand the pathogenesis of cancer and development of new anticancer drugs. Despite of these advancements, many tumors have been found to recur, undergo metastasis and develop resistance to therapy. Accumulated evidences suggest that small population of cancer cells known as cancer stem cells (CSC) are responsible for reconstitution and propagation of the disease. CSCs possess the ability to self-renew, differentiate and proliferate like normal stem cells. CSCs also appear to have resistance to anti-cancer therapies and subsequent relapse. The underlying stemness properties of the CSCs are reliant on multiple molecular targets such as signaling pathways, cell surface molecules, tumor microenvironment, apoptotic pathways, microRNA, stem cell differentiation, and drug resistance markers. Thus an effective therapeutic strategy relies on targeting CSCs to overcome the possible tumor relapse and chemoresistance. The targeted inhibition of these stem cell biomarkers is one of the promising approaches to eliminate cancer stemness. This review article summarizes possible targets of cancer cell stemness for the complete treatment of cancer.

Mapping Aldehyde Dehydrogenase 1A1 Activity using an [18 F]Substrate-Based Approach

Aldehyde dehydrogenases (ALDHs) catalyze the oxidation of aldehydes to carboxylic acids. Elevated ALDH expression in human cancers is linked to metastases and poor overall survival. Despite ALDH being a poor prognostic factor, the non-invasive assessment of ALDH activity in vivo has not been possible due to a lack of sensitive and translational imaging agents. Presented in this report are the synthesis and biological evaluation of ALDH1A1-selective chemical probes composed of an aromatic aldehyde derived from N,N-diethylamino benzaldehyde (DEAB) linked to a fluorinated pyridine ring either via an amide or amine linkage. Of the focused library of compounds evaluated, N-ethyl-6-(fluoro)-N-(4-formylbenzyl)nicotinamide 4 b was found to have excellent affinity and isozyme selectivity for ALDH1A1 in vitro. Following 18 F-fluorination, [18 F]4 b was taken up by colorectal tumor cells and trapped through the conversion to its 18 F-labeled carboxylate product under the action of ALDH. In vivo positron emission tomography revealed high uptake of [18 F]4 b in the lungs and liver, with radioactivity cleared through the urinary tract. Oxidation of [18 F]4 b, however, was observed in vivo, which may limit the tissue penetration of this first-in-class radiotracer.

Biophysical Phenotyping and Modulation of ALDH+ Inflammatory Breast Cancer Stem-Like Cells

Cancer stem-like cells (CSCs) have been shown to initiate tumorigenesis and cancer metastasis in many cancer types. Although identification of CSCs through specific marker expression helps define the CSC compartment, it does not directly provide information on how or why this cancer cell subpopulation is more metastatic or tumorigenic. In this study, the functional and biophysical characteristics of aggressive and lethal inflammatory breast cancer (IBC) CSCs at the single-cell level are comprehensively profiled using multiple microengineered tools. Distinct functional (cell migration, growth, adhesion, invasion and self-renewal) and biophysical (cell deformability, adhesion strength and contractility) properties of ALDH+ SUM149 IBC CSCs are found as compared to their ALDH- non-CSC counterpart, providing biophysical insights into why CSCs has an enhanced propensity to metastasize. It is further shown that the cellular biophysical phenotype can predict and determine IBC cells' tumorigenic ability. SUM149 and SUM159 IBC cells selected and modulated through biophysical attributes-adhesion and stiffness-show characteristics of CSCs in vitro and enhance tumorigenicity in in vivo murine models of primary tumor growth. Overall, the multiparametric cellular biophysical phenotyping and modulation of IBC CSCs yields a new understanding of IBC's metastatic properties and how they might develop and be targeted for therapeutic interventions.

Bortezomib Augments Natural Killer Cell Targeting of Stem-Like Tumor Cells

Tumor cells harboring stem-like/cancer stem cell (CSC) properties have been identified and isolated from numerous hematological and solid malignancies. These stem-like tumor cells can persist following conventional cytoreductive therapies, such as chemotherapy and radiotherapy, thereby repopulating the tumor and seeding relapse and/or metastasis. We have previously shown that natural killer (NK) cells preferentially target stem-like tumor cells via non- major histocompatibility complex (MHC) restricted mechanisms. Here, we demonstrated that the proteasome inhibitor, bortezomib, augments NK cell targeting of stem cell-like tumor cells against multiple solid human tumor-derived cancer lines and primary tissue samples. Mechanistically, this was mediated by the upregulation of cell surface NK ligands MHC class I chain-related protein A and B (MICA and MICB) on aldehyde dehydrogenases (ALDH)-positive CSCs. The increased expression of MICA and MICB on CSC targets thereby enhanced NK cell mediated killing in vitro and ex vivo from both human primary tumor and patient-derived xenograft samples. In vivo, the combination of bortezomib and allogeneic NK cell adoptive transfer in immunodeficient mice led to increased elimination of CSCs as well as tumor growth delay of orthotopic glioblastoma tumors. Taken together, our data support the combination bortezomib and NK transfer as a strategy for both CSC targeting and potentially improved outcomes in clinical cancer patients.

Human Endogenous Formaldehyde as an Anticancer Metabolite: Its Oxidation Downregulation May Be a Means of Improving Therapy

Malignant cells are characterized by an increased content of endogenous formaldehyde formed as a by-product of biosynthetic processes. Accumulation of formaldehyde in cancer cells is combined with activation of the processes of cellular formaldehyde clearance. These mechanisms include increased ALDH and suppressed ADH5/FDH activity, which oncologists consider poor and favorable prognostic markers, respectively. Here, the sources and regulation of formaldehyde metabolism in cancer cells are reviewed. The authors also analyze the participation of oncoproteins such as fibulins, FGFR1, HER2/neu, FBI-1, and MUC1-C in the control of genes related to formaldehyde metabolism, suggesting the existence of two mutually exclusive processes in cancer cells: 1) production and 2) oxidation and elimination of formaldehyde from the cell. The authors hypothesize that the study of the anticancer properties of disulfiram and alpha lipoic acid - which affect the balance of formaldehyde in the body - may serve as the basis of future anticancer therapy.

Chemoproteomics-Enabled Covalent Ligand Screening Reveals ALDH3A1 as a Lung Cancer Therapy Target

Chemical genetics is a powerful approach for identifying therapeutically active small molecules, but identifying the mechanisms of action underlying hit compounds remains challenging. Chemoproteomic platforms have arisen to tackle this challenge and enable rapid mechanistic deconvolution of small-molecule screening hits. Here, we have screened a cysteine-reactive covalent ligand library to identify hit compounds that impair cell survival and proliferation in nonsmall cell lung carcinoma cells, but not in primary human bronchial epithelial cells. Through this screen, we identified a covalent ligand hit, DKM 3-42, which impaired both in situ and in vivo lung cancer pathogenicity. We used activity-based protein profiling to discover that the primary target of DKM 3-42 was the catalytic cysteine in aldehyde dehydrogenase 3A1 (ALDH3A1). We performed further chemoproteomics-enabled covalent ligand screening directly against ALDH3A1, and identified a more potent and selective lead covalent ligand, EN40, which inhibits ALDH3A1 activity and impairs lung cancer pathogenicity. We show here that ALDH3A1 represents a potentially novel therapeutic target for lung cancers that express ALDH3A1 and put forth two selective ALDH3A1 inhibitors. Overall, we show the utility of combining chemical genetics screening of covalent ligand libraries with chemoproteomic approaches to rapidly identify anticancer leads and targets.

Increased Expression of ALDH1A1 in Prostate Cancer is Correlated With Tumor Aggressiveness: A Tissue Microarray Study of Iranian Patients

INTRODUCTION

Subpopulations of prostate cancer (PCa) cells expressing putative stem cell markers possess the ability to promote tumor growth, maintenance, and progression. This study aimed to evaluate the expression patterns and clinical significance of putative stem cell marker aldehyde dehydrogenase 1 A1 (ALDH1A1) in prostate tumor tissues.

MATERIALS AND METHODS

ALDH1A1 expression was examined in a well-defined series of prostate tissues, including 105 (68%) samples of PCa, 21 (13%) samples of high-grade prostatic intraepithelial neoplasia, and 31 (19%) samples of benign prostate hyperplasia, which were embedded in tissue microarray blocks. The correlation of ALDH1A1 expression with clinicopathologic parameters was also assessed.

RESULTS

There was a significant difference between the expression level of ALDH1A1 in PCa compared with the high-grade prostatic intraepithelial neoplasia and benign prostate hyperplasia samples (P<0.001). PCa cells expressing ALDH1A1 were more often seen in samples with advanced Gleason score (P=0.05) and high serum prostate specific antigen level (P=0.02). In addition, a positive correlation was found between ALDH1A1 expression and primary tumor stage and regional lymph node involvement (P=0.04 and 0.03, respectively).

CONCLUSIONS

The significant association between ALDH1A1 expressions with Gleason score indicates the potential role of this protein in PCa tumorigenesis and aggressive behavior; therefore, this cancer stem cell marker can be used as a promising candidate for targeted therapy of PCa, especially those with high Gleason score.

Evaluation of the immunogenicity of ALDH(high) human head and neck squamous cell carcinoma cancer stem cells in vitro

OBJECTIVES

To establish the concept that the antigenicity/immunogenicity of ALDH(high) human head and neck squamous cell carcinoma (HNSCC) cancer stem cells (CSC) is distinct from that of ALDH(low) non-CSCs.

METHODS

We generated CSC-loaded dendritic cells (DCs) to sensitize autologous peripheral blood T, B lymphocytes to react with CSCs using human HNSCC samples in vitro.

RESULTS

From peripheral blood collected from patients with HNSCC, we obtained PBMCs. DCs generated from the PBMC and pulsed with the lysate of ALDH(high) cells isolated from cultured HNSCC cells (CSC-DC) could sensitize autologous T, B lymphocytes in vitro, which was evident by cytokine production, CTL activity, and antibody secretion of these primed T, B cells in response to ALDH(high) CSCs. In contrast, DCs pulsed with lysate of ALDH(low) cells (ALDH(low)-DC) resulted in limited sensitization/priming of autologous T, B lymphocytes to produce IFNγ, GM-CSF; lyse CSCs, and secrete IgM and IgG in response to ALDH(high) CSCs. These results demonstrated significant differences in the antigenicity/immunogenicity between ALDH(high) CSCs vs. ALDH(low) cells isolated from the tumor specimen of patients with HNSCC, which indicates the existence of unique CSC antigens in the ALDH(high) population.

CONCLUSION

It is feasible to generate DCs from the PBMCs and isolate ALDH(high) CSCs from cultured tumor cells of the patients with HNSCC to prepare CSC-DC vaccines that can induce anti-HNSCC CSC cellular and humoral immunity, indicating its potential clinical application to treat patients with HNSCC.

Utilization of lung cancer cell lines for the study of lung cancer stem cells

Lung cancer is one of the most lethal types of cancer, and its poor prognosis is primarily due to drug resistance and cancer recurrence. As it is associated with a low five-year survival rate, lung cancer stem cells (LCSCs) have been the subject of numerous recent studies. For these studies of LCSCs, lung cancer cell lines are more commonly used than lung cancer tissues obtained from patients, as they are easier to acquire. The methods utilized for the identification of LCSCs from lung cancer cell lines include fluorescence activated cell sorting (FACS), magnetic activated cell sorting (MACS), sphere-forming assay and bacterial surface display library screening. As LCSCs have certain proteins expressed on the surface (CD133, CD44 and CD24) or in the cytoplasm (ALDH and ABCG2), which may act as specific markers, the most frequently used technique to identify and obtain LCSCs is FACS. The current lack of recognized biomarkers in LCSCs makes the identification of LCSCs problematic. Furthermore, the various proportions of LCSCs in specific cell lines, as revealed by numerous previous studies, may cause the LCSC model to be questioned with regard to whether the utilization of certain lung cancer cell lines is dependable for LCSC studies. The current review focuses on lung cancer cell lines that are used for the study of LCSCs and the methods available to identify LCSCs with various markers. The present study also aimed to determine the proportion of LCSCs present in specific cell lines reported by various studies, and to discuss the suitability of specific lung cancer cell lines for the study of LCSCs.

Concise Review: Resistance to Tyrosine Kinase Inhibitors in Non-Small Cell Lung Cancer: The Role of Cancer Stem Cells

Among the potential mechanisms involved in resistance to tyrosine kinase inhibitors (TKIs) in non-small cell lung cancer, the manifestation of stem-like properties in cancer cells seems to have a crucial role. Alterations involved in the development of TKI resistance may be acquired in a very early phase of tumorigenesis, supporting the hypothesis that these aberrations may be present in cancer stem cells (CSCs). In this regard, the characterization of tumor subclones in the initial phase and the identification of the CSCs may be helpful in planning a specific treatment to target selected biomarkers, suppress tumor growth, and prevent drug resistance. The aim of this review is to elucidate the role of CSCs in the development of resistance to TKIs and its implication for the management of patients. Stem Cells 2018;36:633-640.

[Research Progress in the Therapeutic Strategy Based on Targeting at Lung Cancer Stem Cell]

With high morbidity and mortality, lung cancer is a major threat to human health and one of the focuses of tumor researches. Lung cancer stem cells (LCSCs) are regarded as a subpopulation of cells within lung cancer tissues with the capacity of self-renewal and differentiation, and might be related to tumorigenesis and heterogeneity of lung cancer. Tumor recurrence, metastasis and drug resistance of lung cancers could be clarified by LCSC hypothesis. Thus it's therapeutically prospective to target at these cells. This review summarizes the biomarkers of LCSCs and their aberrant signal pathways, as well as the therapeutic strategies targeting at LCSCs.

Inhibition of the colony-stimulating-factor-1 receptor affects the resistance of lung cancer cells to cisplatin

In the present work we show that multiple lung cancer cell lines contain cisplatin resistant cell subpopulations expressing the Colony-Stimulating-Factor-Receptor-1 (CSF-1R) and surviving chemotherapy-induced stress. By exploiting siRNA-mediated knock down in vitro and the use of an investigational CSF-1R TKI (JNJ-40346527) in vitro and in vivo, we show that expression and function of the receptor are required for the clonogenicity and chemoresistance of the cell lines. Thus, inhibition of the kinase activity of the receptor reduced the levels of EMT-associated genes, stem cell markers and chemoresistance genes. Additionally, the number of high aldehyde dehydrogenase (ALDH) expressing cells was reduced, consequent to the lack of cisplatin-induced increase of ALDH isoforms. This affected the collective chemoresistance of the treated cultures. Treatment of tumor bearing mice with JNJ-40346527, at pharmacologically relevant doses, produced strong chemo-sensitizing effects in vivo. These anticancer effects correlated with a reduced number of CSF-1Rpos cells, in tumors excised from the treated mice. Depletion of the CD45pos cells within the treated tumors did not, apparently, play a major role in mediating the therapeutic response to the TKI. Thus, lung cancer cells express a functional CSF-1 and CSF-1R duo which mediates pro-tumorigenic effects in vivo and in vitro and can be targeted in a therapeutically relevant way. These observations complement the already known role for the CSF-1R at mediating the pro-tumorigenic properties of tumor-infiltrating immune components.

Subpopulations of cancer stem cells found in papillary thyroid carcinoma

Papillary thyroid carcinoma (PTC) is the most common form of thyroid cancer and while it has a generally good prognosis, tumor recurrence remains a major clinical challenge. Studying laboratory cell lines as well as clinical specimens indicate that PTC may follow the cancer stem cell (CSC) model. However, CSC characteristics relevant in PTC initiation and progression remain largely unknown. Here we studied a population of sphere-growing tumor cells isolated from primary cultures of clinical PTC. These sphere-growing cells consisted of aldehyde dehydrogenase positive (ALDH⁺) and ALDH negative (ALDH^-) cell subpopulations and demonstrated a hierarchical pattern of cell division. Using combinations of selective depletion, specific inhibition and cell sorting, we found that both subpopulations of the sphere cells were able to self-renew and initiate xenograft tumors independently, and fulfilled the definition of CSC. Importantly, when the subpopulations functioned together, the cancer-initiation efficiency and the xenograft tumor progression were significantly enhanced compared to either subpopulation alone. These data revealed crucial roles of ALDH^- CSC in PTC biology and suggested that CSC subpopulations function cooperatively to control PTC initiation and progression. Together, our study indicates that CSC subpopulations isolated from clinical specimens offer unprecedented opportunities for investigating PTC pathogenesis and developing effective therapies.

Cancer stem cells as targets for immunotherapy

Current cancer therapies target the bulk of the tumour, while a population of highly resistant tumour cells may be able to repopulate the tumour and metastasize to new sites. Cancer cells with such stem cell-like characteristics can be identified based on their phenotypical and/or functional features which may open up ways for their targeted elimination. In this review we discuss potential off-target effects of inhibiting cancer stem-cell self-renewal pathways on immune cells, and summarize some recent immunological studies specifically targeting cancer stem cells based on their unique antigen expression.

Gemcitabine treatment causes resistance and malignancy of pancreatic cancer stem-like cells via induction of lncRNA HOTAIR

Gemcitabine is the first-line chemotherapeutic agent for advanced adenocarcinoma of the pancreas, despite the high risk of chemoresistance as a major disadvantage. In the past few years, significant advances have been made in the field of pancreatic cancer stem-like cells (CSCs) and their critical roles in drug resistance, invasion and metastasis, which are tightly regulated by long non-coding RNAs (lncRNAs). The present study demonstrated that HOX antisense intergenic RNA (HOTAIR) is not different between the pancreatic cancer cell line PANC-1 and its enriched CSC sub-population. However, after gemcitabine treatment, the expression levels of HOTAIR in CSCs were induced, but not in PANC-1 cells. HOTAIR induced by gemcitabine failed to cause chemoresistance, but promoted the clonogenicity, proliferation and migration of the cells. By introducing HOTAIR using lentivirus, chemoresistance was induced and the self-renewal capacity, proliferation and migration were significantly promoted. By contrast, HOTAIR knockdown in PANC-1 CSCs treated with or without gemcitabine decreased the cell proliferation, altered the cell cycle progression and induced apoptosis, demonstrating its critical roles in regulating the malignant character of PANC-1 CSCs. In conclusion, the present study demonstrated that HOTAIR may be induced by gemcitabine and acts as a tumor promoter by inhibiting the chemosensitivity, and promoting the self-renewal capacity, proliferation and migration of PANC-1 CSCs, which supports its potential application as a novel therapeutic approach for pancreatic cancer.

Targeting the cancer stem cell marker, aldehyde dehydrogenase 1, to circumvent cisplatin resistance in NSCLC

Non-small cell lung cancer (NSCLC) accounts for a large proportion of cancer deaths and is characterized by low treatment response rates and poor overall prognosis. In the absence of specific treatable mutations, cisplatin-based chemotherapy plays an important role in the treatment of this disease. Unfortunately, the development of resistance has become a major therapeutic challenge in the use of this cytotoxic drug. Elucidating the mechanisms underlying this resistance phenotype, may result in the development of novel agents that enhance sensitivity to cisplatin in lung cancer patients. In this study, targeting the cancer stem cell activity of aldehyde dehydrogenase 1 (ALDH1) was investigated as a strategy to overcome chemoresistance in NSCLC. Tumors from NSCLC patients showed an increase in their profile of pluripotent stemness genes. Cisplatin exposure induced the emergence or expansion of an ALDH1-positive subpopulation in cisplatin sensitive and resistant NSCLC cell lines, respectively, further enhancing cisplatin resistance. Using the Aldefluor assay and FACS analysis, ALDH1 subpopulations were isolated and evaluated in terms of stem cell characteristics. Only ALDH1-positive cells exhibited asymmetric division, cisplatin resistance and increased expression of stem cell factors in vitro. Xenograft studies in NOD/SCID mice demonstrated efficient tumorigenesis from low cell numbers of ALDH1-positive and ALDH1-negative subpopulations. Targeting ALDH1 with Diethylaminobenzaldehyde (DEAB) and Disulfiram, significantly re-sensitized resistant lung cancer cells to the cytotoxic effects of cisplatin. Our data demonstrate the existence of a lung CSC population and suggest a role for targeting ALDH1 as a potential therapeutic strategy in re-sensitizing NSCLC cells to the cytotoxic effects of cisplatin.

NFATc2 enhances tumor-initiating phenotypes through the NFATc2/SOX2/ALDH axis in lung adenocarcinoma

Tumor-initiating cells (TIC) are dynamic cancer cell subsets that display enhanced tumor functions and resilience to treatment but the mechanism of TIC induction or maintenance in lung cancer is not fully understood. In this study, we show the calcium pathway transcription factor NFATc2 is a novel regulator of lung TIC phenotypes, including tumorspheres, cell motility, tumorigenesis, as well as in vitro and in vivo responses to chemotherapy and targeted therapy. In human lung cancers, high NFATc2 expression predicted poor tumor differentiation, adverse recurrence-free and cancer-specific overall survivals. Mechanistic investigations identified NFATc2 response elements in the 3’ enhancer region of SOX2, and NFATc2/SOX2 coupling upregulates ALDH1A1 by binding to its 5’ enhancer. Through this axis, oxidative stress induced by cancer drug treatment is attenuated, leading to increased resistance in a mutation-independent manner. Targeting this axis provides a novel approach for the long-term treatment of lung cancer through TIC elimination.

DOI:http://dx.doi.org/10.7554/eLife.26733.001

Cancer develops when cells become faulty and start to grow uncontrollably. They eventually form lumps or tumors, which may spread to surrounding tissues or even to other areas in the body. One of the reasons why cancer treatment remains a challenge is that there are over 200 types of cells in the body, and there are a lot of moments in the life cycle of a cell when things could go wrong. Researchers have shown that many cancers, including lung cancer, are not only extremely different from patient to patient, but also display great differences between cancer cells within the same tumor.

Increasing evidence suggest that these differences may be caused by a type of cells called tumor initiating cells, or TICs for short. These TICs behave like stem cells and can renew themselves or mature into different types of cells. They are thought to help cancers grow and spread, and even make them resistant to treatments. Previous research has shown that in many types of cancer, the protein NFATc2 helps cancer cells to grow and spread. Until now, however, it was not known if NFATc2 is also important in TICs in lung cancer.

Using human lung cancer cell lines and animal models, Xiao et al. show that the protein NFATc2 stimulates the stem-cell like behavior of TICs. The results showed that TICs had higher levels of the NFATc2 protein than other lung cancer cells that were not TICs. Tumors with higher levels were also more aggressive. When NFATc2 was removed from the cells, they formed smaller tumors and were more sensitive to drug treatment compared to cancer cells with NFATc2.

Further experiments revealed that NFATc2 helped to increase the levels of a protein called Sox2, which gives cells the ability to renew or develop into different cell types. Together, these two proteins stimulated the production of another protein that was already known to play a crucial role in TIC maintenance.

A better understanding of the mechanisms regulating TICs in lung cancer will help scientists tackle new questions about how this cancer progresses and resists to therapy. In the longer-term, combining classic cancer treatments with new therapeutic strategies targeting NFATc2 could make treatments for lung cancer patients more effective.

DOI:http://dx.doi.org/10.7554/eLife.26733.002

Determination of volatile organic compounds exhaled by cell lines derived from hematological malignancies

Background: The gas human exhaled contains many volatile organic compounds (VOCs), which is related to the health status of body. Analysis of VOCs has been proposed as a noninvasive diagnostic tool for certain cancers. Detailed research on the VOCs in gas exhaled by cell can characterize cell type specific metabolites and may be helpful to detect the cancer markers in clinical practice.

Methods: Solid-phase microextraction (SPME) gas chromatography–mass spectrometry was used to detect VOCs in the headspace of tissue culture flask in non-Hodgkin’s lymphoma (NHL) cell line JEKO and acute mononuclear leukemia cell line SHI-1, to elaborate the characteristic gaseous biomarkers of hematological malignancies. While macrophage cells and lymphocytic cells were acted as control. The blank group was only the RPMI 1640 medium containing 10% fetal calf serum that without cells.

Results: Comparing with control group, the concentration of dimethyl sulfide, 2,4-dimethylheptane, methylbenzene, o-xylene, dodecane, and 1,3-di-tert-butylbenzene in JEKO cells was relatively higher, while the concentration of ethanol, hexanal, and benzaldehyde was lower. In SHI-1 cells, the levels of 2,4-dimethylheptane, benzene, 4-methyldecane, chloroform, 3,7-dimethyl dodecane, and hexadecane were significantly elevated, but the levels of hexanol and cyclohexanol were distinctly reduced.

Conclusions: This pilot study revealed that the malignant hematological cells could change the components of VOCs in the cell culture flask in a cell type-specific pattern. The traits of VOCs in our setting offered new strategy for hematological malignancies tracing, and would act as potential biomarkers in diagnosis of malignant hematological diseases.

Targeting Lung Cancer Stem Cells: Research and Clinical Impacts

Lung cancer is the most common cancer worldwide, accounting for 1.8 million new cases and 1.6 million deaths in 2012. Non-small cell lung cancer (NSCLC), which is one of two types of lung cancer, accounts for 85–90% of all lung cancers. Despite advances in therapy, lung cancer still remains a leading cause of death. Cancer relapse and dissemination after treatment indicates the existence of a niche of cancer cells that are not fully eradicated by current therapies. These chemoresistant populations of cancer cells are called cancer stem cells (CSCs) because they possess the self-renewal and differentiation capabilities similar to those of normal stem cells. Targeting the niche of CSCs in combination with chemotherapy might provide a promising strategy to eradicate these cells. Thus, understanding the characteristics of CSCs has become a focus of studies of NSCLC therapies.

Spectroscopic characterisation of interaction of ferulic acid with aldehyde dehydrogenase (ALDH)

Interaction of a pharmacological important phenolic, ferulic acid, with Aldehyde dehydrogenase (ALDH) at the simulative pH condition, was studied using spectroscopic approach. Ferulic acid caused a decrease in the fluorescence intensity formed from ALDH-ferulic acid complex resulting in mixed inhibition of ALDH activity (IC₅₀=30.65μM). The intrinsic quenching was dynamic and induced altered conformation of ALDH and made the protein less compact but might not unfold it. ALDH has two binding sites for ferulic acid at saturating concentrations having association constant of 1.35×10³Lmol^-1 and a dissociation constant of 9.7×10⁷Lmol^-1at 25°C indicating ALDH-ferulic acid complex formation is more favourable than its dissociation. The interaction was not spontaneous and endothermic and suggests the involvement of hydrophobic interactions with a FRET binding distance of 4.49nm. Change in pH near and far from isoelectric points of ferulic acid did not affect the bonding interaction. Using trehalose as viscosogen, the result from Stoke-Einstein hypothesis showed that ferulic acid-ALDH binding and dissociation equilibrium was diffusion controlled. These results clearly suggest the unique binding properties and lipophilicity influence of ferulic acid.

Engineering cancer stem-like cells from normal human lung epithelial cells

It has been proposed that a subpopulation of tumour cells with stem cell-like characteristics, known as cancer stem cells (CSCs), drives tumour initiation and generates tumour heterogeneity, thus leading to cancer metastasis, recurrence, and drug resistance. Although there has been substantial progress in CSC research into many solid tumour types, an understanding of the biology of CSCs in lung cancer remains elusive, mainly because of their heterogeneous origins and high plasticity. Here, we demonstrate that engineered lung cancer cells derived from normal human airway basal epithelial cells possessed CSC-like characteristics in terms of multilineage differentiation potential and strong tumour-initiating ability. Moreover, we established an in vitro 3D culture system that allowed the in vivo differentiation process of the CSC-like cells to be recapitulated. This engineered CSC model provides valuable opportunities for studying the biology of CSCs and for exploring and evaluating novel therapeutic approaches and targets in lung CSCs.

Isolation of cancer progenitor cells from cancer stem cells in gastric cancer

The success of cancer treatment may depend on the complete elimination of cancer stem cells (CSCs). However, data regarding the current characterization of CSCs in different types of tumor are inconsistent, possibly due to the mixture of CSCs with cancer progenitor cells (CPCs). Therefore, it is important to exclude CPCs for the characterization of CSCs. The present study aimed to characterize gastric cancer stem cells (GCSC) by separating GCPC from gastric progenitor cells (GCSC) with flow cytometry. In total, 615 murine gastric cancer (GC) cells were divided into aldehyde dehydrogenase (ALDH)^high, ALDH^low and ALDH^neg groups by flow cytometry according to their ALDH activity. With decreased ALDH activity, the expression levels of stemness-associated markers, CD133⁺, octamer-binding transcription factory-4 and sex determining region Y-box 2 decreased. The ALDH^high and ALDH^low cells proliferated and formed tumor spheres in ultra-low adhesion medium without serum, however, the latter formed larger tumor spheres. In mice transplanted with 5,000 cells, the rate of tumor formation in the ALDH^low group was significantly higher, compared with that in the ALDH^high group. Of note, an increased number of mice developed tumors in the ALDH^high group 16 weeks following the injection of 500 cells, whereas tumors appeared at 8 weeks in the ALDH^low group. The mice in the ALDH^neg group exhibited less tumor formation under these conditions. These results demonstrated that ALDH^high cells had characteristics of GCSCs with a high level of self-renewal ability, but were in a relative resting stage. The ALDH^low cells had characteristics of GCPCs with limited self-renewal ability, but were in a rapid proliferation stage. These findings suggested that the separation of GCPCs from GCSCs is important for elucidating the biology of GCSCs and identifying strategies to eliminate GCSCs in GC.

Use of retinoic acid/aldehyde dehydrogenase pathway as potential targeted therapy against cancer stem cells

A large number of studies have investigated possible drug resistance mechanisms of cancer cells and suggested strategies to overcome it. In this review, we outline the role and function of aldehyde dehydrogenase (ALDH) activity in multiple cellular functions and in cancer stem cells (CSCs) and focus on the role of retinoic acid (RA), one of the products of ALDH isozymes. We discuss our observation that ATRA and other RAs can suppress ALDH activity and decrease different ALDH isozyme proteins and result in detrimental effects on cell proliferation, invasion and chemotherapy sensitivity. We review the known uses of different RAs in the treatment of cancers. We review the use of RAs in combination with chemo-/radiotherapy and the major signaling pathways affected in different tumor types. We provide follow-up on studies that may have used our prior observation with the aim of targeting the CSCs. We conclude with summary of the findings and potential impact of published studies on future use of RAs in the targeting of CSCs and drug resistance.

ALDH/CD44 identifies uniquely tumorigenic cancer stem cells in salivary gland mucoepidermoid carcinomas

A small sub-population of cells characterized by increased tumorigenic potential, ability to self-renew and to differentiate into cells that make up the tumor bulk, has been characterized in some (but not all) tumor types. These unique cells, namedcancer stem cells, are considered drivers of tumor progression in these tumors. The purpose of this work is to understand if cancer stem cells play a functional role in the tumorigenesis of salivary gland mucoepidermoid carcinomas. Here, we investigated the expression of putative cancer stem cell markers (ALDH, CD10, CD24, CD44) in primary human mucoepidermoid carcinomas by immunofluorescence, in vitro salisphere assays, and in vivo tumorigenicity assays in immunodeficient mice. Human mucoepidermoid carcinoma cells (UM-HMC-1, UM-HMC-3A, UM-HMC-3B) sorted for high levels of ALDH activity and CD44 expression (ALDHhighCD44high) consistently formed primary and secondary salispheres in vitro, and showed enhanced tumorigenic potential in vivo (defined as time to tumor palpability, tumor growth after palpability), when compared to ALDHlowCD44low cells. Cells sorted for CD10/CD24, and CD10/CD44 showed varying trends of salisphere formation, but consistently low in vivo tumorigenic potential. And finally, cells sorted for CD44/CD24 showed inconsistent results in salisphere formation and tumorigenic potential assays when different cell lines were evaluated. Collectively, these data demonstrate that salivary gland mucoepidermoid carcinomas contain a small population of cancer stem cells with enhanced tumorigenic potential and that are characterized by high ALDH activity and CD44 expression. These results suggest that patients with mucoepidermoid carcinoma might benefit from therapies that ablate these highly tumorigenic cells.

IL-8 confers resistance to EGFR inhibitors by inducing stem cell properties in lung cancer

Epidermal growth factor receptor (EGFR)-targeted strategy is limited by resistance. We identify the potential genes involved in EGFR TKI (tyrosine kinase inhibitor) resistance and study the therapeutic mechanism in the non-small cell lung cancers. Potential genes involved in resistance were examined by analyzing datasets from a pair of EGFR TKI-sensitive (PC9) and TKI-resistant cells (PC9/gef). Blood specimens from patients taking EGFR TKI as first-line treatment were used to examine the correlation between drug's efficacy and IL-8 level. The effects of IL-8 on gefitinib-induced apoptosis, stemness, and in vivo tumorigenicity were investigated using established cell lines. We identified IL-8 was up-regulated in gefitinib-resistant cells, and high plasma IL-8 level was correlated with shorter progression-free-survival time. IL-8 overexpression suppressed gefitinib-induced apoptosis in gefitinib-sensitive cells. By contrast, suppression of IL-8 enhanced gefitinib-induced cell death in gefitinib-resistant cells. IL-8 also increased stem-like characteristics including aldehyde dehydrogenase activity, expression of stemness-related genes, clonogenic activity, side-population, and in vivo tumorigenicity. Consistently, knockdown of IL-8 leads to loss of stem cell-like characteristics in gefitinib-resistant cells. Our study demonstrates an important role for IL-8, and suggests IL-8 is a potential therapeutic target for overcoming EGFR TKI resistance.

Detection of ALDH1 activity in rabbit hepatic VX2 tumors and isolation of ALDH1 positive cancer stem cells

Background

Aldehyde dehydrogenase 1 (ALDH1) activity has been implicated in the therapeutic drug resistance of many malignancies and has been widely used as a marker to identify stem-like cells, including in primary liver cancer. Cancer stem cells (CSCs) are thought to play a crucial role in cancer progression and metastasis. In order to clarify the validity of the rabbit VX2 liver cancer model, we questioned if it expresses ALDH1 as a potential marker of CSCs. Hepatocellular carcinoma is a common malignancy worldwide and has poor prognosis. Most of the animal models used to study hepatocellular carcinoma are rodent models which lack clinical relevance. The rabbit VX2 model is a large animal model useful for preclinical and for developing drugs targeting cancer stem cells.

Materials and methods

We used flow cytometry to identify rabbit VX2 liver tumor cells that express ALDH1A1 activity at a high level and confirmed the results with RT-PCR, immunohistochemical and western blot analyses. Further, mRNA and protein expression analysis of tumor samples also express the markers for stemness like klf4, oct3/4, CD44 and nanog as well as the differentiation marker α-fetoprotein.

Results

We used Aldefluor flow cytometry-based assay to identify cells with high ALDH1 activity in the rabbit VX2 liver cancer model. We used the brightest 4.39 % of the total cancer cell population in our study. We performed semi-quantitative as well as real time PCR to characterize the stemness derived from VX2 tumors and tissues from normal rabbit liver. We demonstrated that VX2 tumors have higher expression of cancer stem cell markers such as AlDH1A1 and CD44 in comparison to normal rabbit liver cells. Additionally, real time PCR analysis of the same samples using syber-green demonstrated the significant change (p > 0.05) in the expression of genes. We validated the gene expression of the stemness markers by performing western blot and immunofluorescence. We showed that cancer stem cell markers (AlDH1A1, CD44) and the differentiation marker α-fetoprotein were upregulated in VX2 tumor cells. The same extent of upregulation was observed in stemness markers (klf4, oct3/4 and nanog) in VX2 tumors in comparison to normal rabbit liver.

Conclusion

The overall results of this study indicate that ALDH1 is a valid CSC marker for VX2 cancer. This finding suggests that the rabbit VX2 liver cancer model is useful in studying drug resistance in hepatocellular carcinoma and may be useful for basic and preclinical studies of other types of human cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-016-0785-0) contains supplementary material, which is available to authorized users.

Mucin 1-mediated chemo-resistance in lung cancer cells

Paclitaxel (PTX) is a commonly used drug to treat diverse cancer types. However, its treatment can generate resistance and the mechanisms of PTX-resistance in lung cancers are still unclear. We demonstrated that non-small cell lung cancers (NSCLCs) survive PTX treatment. Compared with the progenitor NSCLC A549 cells, the PTX-resistant A549 cells (A549/PTX) displayed enhanced sphere-formation ability. The proportion of the cancer stem cell marker, aldehyde dehydrogenase-positive cells, and epithelial-mesenchymal transition signaling protein levels were also elevated in A549/PTX. Importantly, the levels of oncoproteins phosphoinositide-3 kinase/Akt, mucin 1 cytoplasmic domain (MUC1-C) and β-catenin were also significantly elevated in A549/PTX. Furthermore, nuclear translocation of MUC1-C and β-catenin increased in A549/PTX. The c-SRC protein, an activator of MUC1-C, was also overexpressed in A549/PTX. These observations led to the hypothesis that enhanced expression of MUC1-C is associated with stemness and PTX resistance in NSCLCs. To test this, we knocked down or overexpressed MUC1-C in A549/PTX and found that inhibition of MUC1-C expression coupled with PTX treatment was sufficient to reduce the sphere-forming ability and survival of A549/PTX. In summary, our in vitro and in vivo studies have revealed a potential mechanism of MUC1-C-mediated PTX resistance and provided insights into a novel therapeutic measure for lung cancers.

Cancer stem cells: a metastasizing menace!

Cancer is one of the leading causes of death worldwide, and is estimated to be a reason of death of more than 18 billion people in the coming 5 years. Progress has been made in diagnosis and treatment of cancer; however, a sound understanding of the underlying cell biology still remains an unsolved mystery. Current treatments include a combination of radiation, surgery, and/or chemotherapy. However, these treatments are not a complete cure, aimed simply at shrinking the tumor and in majority of cases, there is a relapse of tumor. Several evidences suggest the presence of cancer stem cells (CSCs) or tumor‐initiating stem‐like cells, a small population of cells present in the tumor, capable of self‐renewal and generation of differentiated progeny. The presence of these CSCs can be attributed to the failure of cancer treatments as these cells are believed to exhibit therapy resistance. As a result, increasing attention has been given to CSC research to resolve the therapeutic problems related to cancer. Progress in this field of research has led to the development of novel strategies to treat several malignancies and has become a hot topic of discussion. In this review, we will briefly focus on the main characteristics, therapeutic implications, and perspectives of CSCs in cancer therapy.

Isolation and Characterization of Cancer Stem Cells of the Non-Small-Cell Lung Cancer (A549) Cell Line

Cancer is a major health problem worldwide. The failure of current treatments to completely eradicate cancer cells often leads to cancer recurrence and dissemination. Studies have suggested that tumor growth and spread are driven by a minority of cancer cells that exhibit characteristics similar to those of normal stem cells, thus these cells are called cancer stem cells (CSCs). CSCs are believed to play an important role in initiating and promoting cancer. CSCs are resistant to currently available cancer therapies, and understanding the mechanisms that control the growth of CSCs might have great implications for cancer therapy. Cancer cells are consist of heterogeneous population of cells, thus methods of identification, isolation, and characterisation of CSCs are fundamental to obtain a pure CSC populations. Therefore, this chapter describes in detail a method for isolating and characterizing a pure population of CSCs from heterogeneous population of cancer cells and CSCs based on specific cell surface markers.

Cancer stem cells in drug resistant lung cancer: Targeting cell surface markers and signaling pathways

Lung cancer is the leading cause of cancer mortality worldwide. Despite advances in anti-cancer therapies such as chemotherapy, radiotherapy and targeted therapies, five-year survival rates remain poor (<15%). Inherent and acquired resistance has been identified as a key factor in reducing the efficacy of current cytotoxic therapies in the management of non-small cell lung cancer (NSCLC). There is growing evidence suggesting that cancer stem cells (CSCs) play a critical role in tumor progression, metastasis and drug resistance. Similar to normal tissue stem cells, CSCs exhibit significant phenotypic and functional heterogeneity. While CSCs have been reported in a wide spectrum of human tumors, the biology of CSCs in NSCLC remain elusive. Current anti-cancer therapies fail to eradicate CSC clones and instead, favor the expansion of the CSC pool and select for resistant CSC clones thereby resulting in treatment resistance and subsequent relapse in these patients. The identification of CSC-specific marker subsets and the targeted therapeutic destruction of CSCs remains a significant challenge. Strategies aimed at efficient targeting of CSCs are becoming increasingly important for monitoring the progress of cancer therapy and for evaluating new therapeutic approaches. This review focuses on the current knowledge of cancer stem cell markers in treatment-resistant lung cancer cells and the signaling cascades activated by these cells to maintain their stem-like properties. Recent progress in CSC-targeted drug development and the current status of novel agents in clinical trials are also reviewed.

Microbial influences on hormesis, oncogenesis, and therapy: A review of the literature

Utilization of environmental stimuli for growth is the main factor contributing to the evolution of prokaryotes and eukaryotes, independently and mutualistically. Epigenetics describes an organism's ability to vary expression of certain genes based on their environmental stimuli. The diverse degree of dose-dependent responses based on their variances in expressed genetic profiles makes it difficult to ascertain whether hormesis or oncogenesis has or is occurring. In the medical field this is shown where survival curves used in determining radiotherapeutic doses have substantial uncertainties, some as large as 50% (Barendsen, 1990). Many in-vitro radiobiological studies have been limited by not taking into consideration the innate presence of microbes in biological systems, which have either grown symbiotically or pathogenically. Present in-vitro studies neglect to take into consideration the varied responses that commensal and opportunistic pathogens will have when exposed to the same stimuli and how such responses could act as stimuli for their macro/microenvironment. As a result many theories such as radiation carcinogenesis explain microscopic events but fail to describe macroscopic events (Cohen, 1995). As such, this review shows how microorganisms have the ability to perturb risks of cancer and enhance hormesis after irradiation. It will also look at bacterial significance in the microenvironment of the tumor before and during treatment. In addition, bacterial systemic communication after irradiation and the host's immune responses to infection could explain many of the phenomena associated with bystander effects. Therefore, the present literature review considers the paradigms of hormesis and oncogenesis in order to find a rationale that ties them all together. This relationship was thus characterized to be the microbiome.