ALDH Activity Correlates with Metastatic Potential in Primary Sarcomas of Bone

RNA-sequencing predicts a role of androgen receptor and aldehyde dehydrogenase 1A1 in osteosarcoma lung metastases

One-third of pediatric patients with osteosarcoma (OS) develop lung metastases (LM), which is the primary predictor of mortality. While current treatments of patients with localized bone disease have been successful in producing 5-year survival rates of 65-70%, patients with LM experience poor survival rates of only 19-30%. Unacceptably, this situation that has remained unchanged for 30 years. Thus, there is an urgent need to elucidate the mechanisms of metastatic spread in OS and to identify targetable molecular pathways that enable more effective treatments for patients with LM. We aimed to identify OS-specific gene alterations using RNA-sequencing of extremity and LM human tissues. Samples of extremity and LM tumors, including 4 matched sets, were obtained from patients with OS. Our data demonstrate aberrant regulation of the androgen receptor (AR) pathway in LM and predicts aldehyde dehydrogenase 1A1 (ALDH1A1) as a downstream target. Identification of AR pathway upregulation in human LM tissue samples may provide a target for novel therapeutics for patients with LM resistant to conventional chemotherapy.

Nε-(1-Carboxymethyl)-L-lysine/RAGE Signaling Drives Metastasis and Cancer Stemness through ERK/NFκB axis in Osteosarcoma

Osteosarcoma is an extremely aggressive bone cancer with poor prognosis. Nε-(1-Carboxymethyl)-L-lysine (CML), an advanced glycation end product (AGE), can link to cancer progression, tumorigenesis and metastasis, although the underlying mechanism remains unclear. The role of CML in osteosarcoma progression is still unclear. We hypothesized that CML could promote migration, invasion, and stemness in osteosarcoma cells. CML and its receptor (RAGE; receptor for AGE) were higher expressed at advanced stages in human osteosarcoma tissues. In mouse models, which streptozotocin was administered to induce CML accumulation in the body, the subcutaneous tumor growth was not affected, but the tumor metastasis using tail vein injection model was enhanced. In cell models (MG63 and U2OS cells), CML enhanced tumor sphere formation and acquisition of cancer stem cell characteristics, induced migration and invasion abilities, as well as triggered the epithelial-mesenchymal transition process, which were associated with RAGE expression and activation of downstream signaling pathways, especially the ERK/NFκB pathway. RAGE inhibition elicited CML-induced cell migration, invasion, and stemness through RAGE-mediated ERK/NFκB pathway. These results revealed a crucial role for CML in driving stemness and metastasis in osteosarcoma. These findings uncover a potential CML/RAGE connection and mechanism to osteosarcoma progression and set the stage for further investigation.

Effect of ALDH1A1 and CD44 on Survival and Disease Recurrence in Patients With Osteosarcoma

PURPOSE

Emerging evidence suggests that osteosarcoma stem cells (OSCs) may be responsible for tumor initiation propagation, recurrence, and resistance to therapy. We set out to evaluate the relationship between the abundance of ALDH1A1 and CD44-positive cells in biopsy and resection samples on disease recurrence and overall survival.

METHODS

A retrospective review of 20 patients, including biopsy and resection samples, was performed at a comprehensive cancer center. Additionally, we queried the publicly available TARGET dataset of osteosarcoma patients.

RESULTS

Neither the percentages of ALDH1A1-positive cells nor CD44-positive cells were significantly associated with overall mortality or disease recurrence in either biopsy or resection samples. Unlike our institutional data, overall survival was significantly correlated to higher ALDH1A1 expression in the TARGET dataset both in univariate and age-adjusted analyses.

CONCLUSIONS

ADLH1 and CD44, potential markers of OSCs, were not found to be reliable clinical immunohistochemical prognostic markers for osteosarcoma patient survival, specifically disease-free survival. Osteosarcoma patients with high ALDH1A1 RNA expression showed improved overall survival in examining a national genomic database of osteosarcoma patients but again no association with disease-free survival. The potential of CD44 and ALDH1A1 as cellular-specific prognostic markers of survival, and as possible molecular targets, may be limited in osteosarcoma.

Antioxidant 1 copper chaperone gene expression and copper levels in dog osteosarcoma patients

Twenty-four dogs with OS underwent limb amputation. Serum, OS tumour, and normal bone were harvested at time of surgery. RNA was extracted and gene expression was performed using quantitative polymerase chain reaction (qPCR). Tissue and blood copper concentrations were also determined with spectrophotometry. Compared to bone, tumour samples had significantly higher expressions of antioxidant 1 copper chaperone (ATOX1, p = .0003). OS tumour copper levels were significantly higher than that of serum (p < .010) and bone (p = .038). Similar to our previous observations in mouse and human OS, dog OS demonstrates overexpression of genes that regulate copper metabolism (ATOX1), and subsequent copper levels. Dogs with OS may provide a robust comparative oncology platform for the further study of these factors, as well as potential pharmacologic interventions.

Disulfiram suppresses epithelial-mesenchymal transition (EMT), migration and invasion in cervical cancer through the HSP90A/NDRG1 pathway

Disulfiram (DSF) has proven to be a promising anti-tumor drug in preclinical studies. However, its anti-cancer mechanism has not yet been elucidated. As an activator in tumor metastasis, N-myc downstream regulated gene-1 (NDRG1) is involved in multiple oncogenic signaling pathways and is upregulated by cell differentiation signals in various cancer cell lines. DSF treatment results in a significant reduction in NDRG1, while down-regulated NDRG1 has a pronounced effect on invading cancer cells, as shown in our previous work. Here, in vitro and in vivo experiments confirm that DSF contributes to regulating tumor growth, EMT, and the migration and invasion of cervical cancer. Furthermore, our results show DSF binds to the ATP-binding pocket in the N-terminal domain of HSP90A, thereby affecting the expression of its client protein NDRG1. To our knowledge, this is the first report of DSF binding to HSP90A. In conclusion, this study sheds light on the molecular mechanism by which DSF inhibits tumor growth and metastasis through the HSP90A/NDRG1/β-catenin pathway in cervical cancer cells. These findings provide novel insights into the mechanism underlying DSF function in cancer cells.

Cellular and Genetic Background of Osteosarcoma

Osteosarcoma describes a tumor of mesenchymal origin with an annual incidence rate of four to five people per million. Even though chemotherapy treatment has shown success in non-metastatic osteosarcoma, metastatic disease still has a low survival rate of 20%. A targeted therapy approach is limited due to high heterogeneity of tumors, and different underlying mutations. In this review, we will summarize new advances obtained by new technologies, such as next generation sequencing and single-cell sequencing. These new techniques have enabled better assessment of cell populations within osteosarcoma, as well as an understanding of the molecular pathogenesis. We also discuss the presence and properties of osteosarcoma stem cells-the cell population within the tumor that is responsible for metastasis, recurrence, and drug resistance.

Cancer Stem Cells in Sarcomas: In Vitro Isolation and Role as Prognostic Markers: A Systematic Review

Sarcomas are a diverse group of neoplasms with an incidence rate of 15% of childhood cancers. They exhibit a high tendency to develop early metastases and are often resistant to available treatments, resulting in poor prognosis and survival. In this context, cancer stem cells (CSCs) have been implicated in recurrence, metastasis, and drug resistance, making the search for diagnostic and prognostic biomarkers of the disease crucial. The objective of this systematic review was to analyze the expression of CSC biomarkers both after isolation from in vitro cell lines and from the complete cell population of patient tumor samples. A total of 228 publications from January 2011 to June 2021 was retrieved from different databases, of which 35 articles were included for analysis. The studies demonstrated significant heterogeneity in both the markers detected and the CSC isolation techniques used. ALDH was identified as a common marker in various types of sarcomas. In conclusion, the identification of CSC markers in sarcomas may facilitate the development of personalized medicine and improve treatment outcomes.

Chondrosarcoma Resistance to Radiation Therapy: Origins and Potential Therapeutic Solutions

Chondrosarcoma is a malignant cartilaginous tumor that is particularly chemoresistant and radioresistant to X-rays. The first line of treatment is surgery, though this is almost impossible in some specific locations. Such resistances can be explained by the particular composition of the tumor, which develops within a dense cartilaginous matrix, producing a resistant area where the oxygen tension is very low. This microenvironment forces the cells to adapt and dedifferentiate into cancer stem cells, which are described to be more resistant to conventional treatments. One of the main avenues considered to treat this type of tumor is hadrontherapy, in particular for its ballistic properties but also its greater biological effectiveness against tumor cells. In this review, we describe the different forms of chondrosarcoma resistance and how hadrontherapy, combined with other treatments involving targeted inhibitors, could help to better treat high-grade chondrosarcoma.

The Concept of Cancer Stem Cells: Elaborating on ALDH1B1 as an Emerging Marker of Cancer Progression

Cancer is a multifactorial, complex disease exhibiting extraordinary phenotypic plasticity and diversity. One of the greatest challenges in cancer treatment is intratumoral heterogeneity, which obstructs the efficient eradication of the tumor. Tumor heterogeneity is often associated with the presence of cancer stem cells (CSCs), a cancer cell sub-population possessing a panel of stem-like properties, such as a self-renewal ability and multipotency potential. CSCs are associated with enhanced chemoresistance due to the enhanced efflux of chemotherapeutic agents and the existence of powerful antioxidant and DNA damage repair mechanisms. The distinctive characteristics of CSCs make them ideal targets for clinical therapeutic approaches, and the identification of efficient and specific CSCs biomarkers is of utmost importance. Aldehyde dehydrogenases (ALDHs) comprise a wide superfamily of metabolic enzymes that, over the last years, have gained increasing attention due to their association with stem-related features in a wide panel of hematopoietic malignancies and solid cancers. Aldehyde dehydrogenase 1B1 (ALDH1B1) is an isoform that has been characterized as a marker of colon cancer progression, while various studies suggest its importance in additional malignancies. Here, we review the basic concepts related to CSCs and discuss the potential role of ALDH1B1 in cancer development and its contribution to the CSC phenotype.

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.

Morpholino-driven blockade of Dkk-1 in osteosarcoma inhibits bone damage and tumour expansion by multiple mechanisms

Background

Osteosarcoma (OS) is the most common primary bone malignancy. Chemotherapy plays an essential role in OS treatment, potentially doubling 5-year event-free survival if tumour necrosis can be stimulated. The canonical Wnt inhibitor Dickkopf-1 (Dkk-1) enhances OS survival in part through upregulation of aldehyde-dehydrogenase-1A1 which neutralises reactive oxygen species originating from nutritional stress and chemotherapeutic challenge.

Methods

A vivo morpholino (DkkMo) was employed to block the expression of Dkk-1 in OS cells. Cell mitosis, gene expression and bone destruction were measured in vitro and in vivo in the presence and absence of doxorubicin (DRB).

Results

DkkMo reduced the expression of Dkk-1 and Aldh1a1, reduced expansion of OS tumours, preserved bone volume and architecture and stimulated tumour necrosis. This was observed in the presence or absence of DRB.

Conclusion

These results indicate that administration of DkkMo with or without chemotherapeutics can substantially improve OS outcome with respect to tumour expansion and osteolytic corruption of bone in experimental OS model.

ALDH1A1 Gene Expression and Cellular Copper Levels between Low and Highly Metastatic Osteosarcoma Provide a Case for Novel Repurposing with Disulfiram and Copper

Aldehyde dehydrogenase 1A1 (ALDH) is a cancer stem cell marker highly expressed in metastatic cells. Disulfiram (Dis) is an FDA-approved antialcoholism drug that inhibits ALDH and has been studied as a candidate for drug repurposing in multiple neoplasia. Dis cytotoxicity in cancer cells has been shown to be copper-dependent, in part due to Dis's ability to function as a bivalent metal ion chelator of copper (Cu). The objectives of this research were to test ALDH expression levels and Cu concentrations in sarcoma patient tumors and human osteosarcoma (OS) cell lines with differing metastatic phenotypes. We also sought to evaluate Dis + Cu combination therapy in human OS cells. Intracellular Cu was inversely proportional to the metastatic phenotype in human OS cell lines (SaOS2 > LM2 > LM7). Nonmetastatic human sarcoma tumors demonstrated increased Cu concentrations compared with metastatic tumors. qPCR demonstrated that ALDH expression was significantly increased in highly metastatic LM2 and LM7 human OS cell lines compared with low metastatic SaOS2. Tumor cells from sarcoma patients with metastatic disease displayed significantly increased ALDH expression compared with tumor cells from patients without metastatic disease. Serum Cu concentration in canine OS versus normal canine patients demonstrated similar trends. Dis demonstrated selective cytotoxicity compared with human multipotential stromal cells (MSCs): Dis-treated OS cells demonstrated increased apoptosis, whereas MSCs did not. CuCl₂ combined with Dis and low-dose doxorubicin resulted in a superior cytotoxic effect in both SaOS2 and LM7 cell lines. In summary, ALDH gene expression and Cu levels are altered between low and highly metastatic human OS cells, canine samples, and patient tumors. Our findings support the feasibility of a repurposed drug strategy for Dis and Cu in combination with low-dose anthracycline to specifically target metastatic OS cells.

Quantitative proteomics analysis reveals novel insights into mechanisms of action of disulfiram (DSF)

PURPOSE

Disulfiram (DSF) has been proven safe and shows the promising antitumor effect in preclinical studies. However, the precise mechanism of DSF on tumor is rarely reported. This study aims to fully understand the mechanism of action of DSF with a systems perspective in anticancer effects.

EXPERIMENTAL DESIGN

SILAC-based quantitative proteomics strategy was used to systematically identify differential expression proteins (DEPs) after DSF treatment in HeLa cells. Bioinformatical analysis (PANTHER, DAVID, and STRING) were performed to characterize biological functions of DEPs. Functional studies were performed to explore underlying mechanisms of DSF in cancer cells.

RESULTS

In total, 201 proteins were dysregulated significantly after DSF exposure. Functional studies of hexokinase 2 (HK2), which catalyzed the first irreversible enzymatic step in glucose metabolism, revealed that various phenotypic effects observed after DSF treatment in cancer cells, at least partly, through the regulation of HK2 expression.

CONCLUSIONS AND CLINICAL RELEVANCE

By correlating the proteomics data with these functional studies, the current results provided novel insights into the mechanism underlying DSF function in cancer cells. Meanwhile, these provided theoretical basis for the new use of old drugs in clinical therapy.

Cancer Stem Cells as a Source of Drug Resistance in Bone Sarcomas

Bone sarcomas are commonly characterized by a high degree of intra-tumor heterogeneity, which in part is due to the presence of subpopulations of tumor cells presenting stem cell properties. Similar to normal stem cells, these cancer stem cells (CSCs) display a drug resistant phenotype and therefore are responsible for relapses and tumor dissemination. Drug resistance in bone sarcomas could be enhanced/modulated during tumor evolution though the acquisition of (epi)-genetic alterations and the adaptation to changing microenvironments, including drug treatments. Here we summarize findings supporting the involvement of pro-stemness signaling in the development of drug resistance in bone sarcomas. This include the activation of well-known pro-stemness pathways (Wnt/β-Cat, NOTCH or JAT/STAT pathways), changes in the metabolic and autophagic activities, the alteration of epigenetic pathways, the upregulation of specific non-coding RNAs and the crosstalk with different microenvironmental factors. This altered signaling is expected to be translated to the clinic in the form of biomarkers of response and new therapies able to overcome drug resistance.

Update on Osteosarcoma

PURPOSE OF REVIEW

Osteosarcoma (OSA) is the most common primary tumor of bone, mainly affecting children and adolescents. Here we discuss recent advances in surgical and systemic therapies, and highlight potentially new modalities in preclinical evaluation and prognostication.

RECENT FINDINGS

The advent of neoadjuvant and adjuvant chemotherapy has markedly improved the disease-free recurrence and overall survival of OSA. However, treatment efficacy has been stagnant since the 1980s. This plateau has prompted preclinical and clinical research into in precision surgery, inhaled chemotherapy to increase pulmonary drug concentration without systemic side effects, and novel immunomodulators intended to block molecular pathways associated with OSA proliferation and metastasis. With the advent of novel surgical techniques and new forms and vectors for chemotherapy, it is hoped that OSA treatment outcomes will exceed their currently sustained plateau in the near future.

Do Patient-derived Spheroid Culture Models Have Relevance in Chondrosarcoma Research?

BACKGROUND

In high-grade chondrosarcoma, 5-year survival is lower than 50%. Therefore, it is important that preclinical models that mimic the disease with the greatest possible fidelity are used to potentially develop new treatments. Accumulating evidence suggests that two-dimensional (2-D) cell culture may not accurately represent the tumor's biology. It has been demonstrated in other cancers that three-dimensional (3-D) cancer cell spheroids may recapitulate tumor biology and response to treatment with greater fidelity than traditional 2-D techniques. To our knowledge, the formation of patient-derived chondrosarcoma spheroids has not been described.

QUESTIONS/PURPOSES

(1) Can patient-derived chondrosarcoma spheroids be produced? (2) Do spheroids recapitulate human chondrosarcoma better than 2-D cultures, both morphologically and molecularly? (3) Can chondrosarcoma spheroids provide an accurate model to test novel treatments?

METHODS

Experiments to test the feasibility of spheroid formation of chondrosarcoma cells were performed using HT-1080, an established chondrosarcoma cell line, and two patient-derived populations, TP19-S26 and TP19-S115. Cells were cultured in flasks, trypsinized, and seeded into 96-well ultra-low attachment plates with culture media. After spheroids formed, they were monitored daily by bright-field microscopy. Spheroids were fixed using paraformaldehyde and embedded in agarose. After dehydration with isopropanol, paraffin-embedded spheroids were sectioned, and slides were stained with hematoxylin and eosin. To compare differences and similarities in gene expression between 2-D and 3-D chondrosarcoma cultures and primary tumors, and to determine whether these spheroids recapitulated the biology of chondrosarcoma, RNA was extracted from 2-D cultures, spheroids, and tumors. Quantitative polymerase chain reaction was performed to detect chondrosarcoma markers of interest, including vascular endothelial growth factor alpha, hypoxia-inducible factor 1α, COL2A1, and COL10A1. To determine whether 2-D and 3-D cultures responded differently to novel chondrosarcoma treatments, we compared their sensitivities to disulfiram and copper chloride treatment. To test their sensitivity to disulfiram and copper chloride treatment, 10,000 cells were seeded into 96-well plates for 2-D culturing and 3000 cells in each well for 3-D culturing. After treating the cells with disulfiram and copper for 48 hours, we detected cell viability using quantitative presto-blue staining and measured via plate reader.

RESULTS

Cell-line and patient-derived spheroids were cultured and monitored over 12 days. Qualitatively, we observed that HT-1080 demonstrated unlimited growth, while TP19-S26 and TP19-S115 contracted during culturing relative to their initial size. Hematoxylin and eosin staining of HT-1080 spheroids revealed that cell-cell attachments were more pronounced at the periphery of the spheroid structure than at the core, while the core was less dense. Spheroids derived from the intermediate-grade chondrosarcoma TP19-S26 were abundant in extracellular matrix, and spheroids derived from the dedifferentiated chondrosarcoma TP19-S115 had a higher cellularity and heterogeneity with spindle cells at the periphery. In the HT-1080 cells, differences in gene expression were appreciated with spheroids demonstrating greater expressions of VEGF-α (1.01 ± 0.16 versus 6.48 ± 0.55; p = 0.003), COL2A1 (1.00 ± 0.10 versus 7.46 ± 2.52; p < 0.001), and COL10A1 (1.01 ± 0.19 versus 22.53 ± 4.91; p < 0.001). Differences in gene expressions were also noted between primary tumors, spheroids, and 2-D cultures in the patient-derived samples TP19-S26 and TP19-S115. TP19-S26 is an intermediate-grade chondrosarcoma. With the numbers we had, we could not detect a difference in VEGF-α and HIF1α gene expression compared with the primary tumor. COL2A1 (1.00 ± 0.14 versus 1.76 ± 0.10 versus 335.66 ± 31.13) and COL10A1 (1.06 ± 0.378 versus 5.98 ± 0.45 versus 138.82 ± 23.4) expressions were both greater in the tumor (p (COL2A1) < 0.001; p (COL10A1) < 0.0001) and 3-D cultures (p (COL2A1) = 0.004; p (COL10A1) < 0.0001) compared with 2-D cultures. We could not demonstrate a difference in VEGF-α and HIF1α expressions in TP19-S115, a dedifferentiated chondrosarcoma, in the tumor compared with 2-D and 3-D cultures. COL2A1 (1.00 ± 0.02 versus 1.86 ± 0.18 versus 2.95 ± 0.56) and COL10A1 (1.00 ± 0.03 versus 5.52 ± 0.66 versus 3.79 ± 0.36) expressions were both greater in spheroids (p (COL2A1) = 0.003; p (COL10A1) < 0.0001) and tumors (p (COL2A1) < 0.001; p (COL10A1) < 0.0001) compared with 2-D cultures. Disulfiram-copper chloride treatment demonstrated high cytotoxicity in HT-1080 and SW-1353 chondrosarcoma cells grown in the 2-D monolayer, but 3-D spheroids were highly resistant to this treatment.

CONCLUSION

We provide preliminary findings that it is possible to generate 3-D spheroids from chondrosarcoma cell lines and two human chondrosarcomas (one dedifferentiated chondrosarcoma and one intermediate-grade chondrosarcoma). Chondrosarcoma spheroids derived from human tumors demonstrated morphology more reminiscent of primary tumors than cells grown in 2-D culture. Spheroids displayed similar expressions of cartilage markers as the primary tumor, and we observed a higher expression of collagen markers in the spheroids compared with cells grown in monolayer. Spheroids also demonstrated greater chemotherapy resistance than monolayer cells, but more patient-derived spheroids are needed to further conclude that 3-D cultures may mimic the chemoresistance that chondrosarcomas demonstrate clinically. Additional studies on patient-derived chondrosarcoma spheroids are warranted.

CLINICAL RELEVANCE

Chondrosarcomas demonstrate resistance to chemotherapy and radiation, and we believe that if they can be replicated, models such as 3-D spheroids may provide a method to test novel treatments for human chondrosarcoma. Additional comprehensive genomic studies are required to compare 2-D and 3-D models with the primary tumor to determine the most effective way to study this disease in vitro.

ALDH Expression in Angiosarcoma of the Lung: A Potential Marker of Aggressiveness?

Background: Primary angiosarcoma of the lung is a very aggressive rare malignant disease resulting in a severe prognosis (1). This type of cancer represents about 2% of all soft tissue sarcomas and has a high rate of metastasis through the hematogenous route. For the rarity of this malignant vascular tumor it is still challenging to set a diagnosis (1). The diagnostic features that have thus far been considered include primarily clinical and radiological findings. In some cases, immunohistochemical characteristics based on the most common markers used in pathology have been described. The aim of this report is to present two cases of angiosarcoma of the lung in which the aldehyde dehydrogenase (ALDH) marker was analyzed by immunohistochemistry.

Methods: We report two cases of angiosarcoma of the lung in patients underwent lung surgery at our Unit. In addition to the standard histopathological analysis for this disease, immunohistochemistry using an ALDH1A1 antibody was performed in both of the cases. For ALDH quantification, a semi-quantitative method based on the positivity of the tumor cells was used: 0 (<5%), 1 (5–25%), 2 (>25–50%), 3 (>50–75%), 4 (>75%).

Results: One patient with recurrent lung disease survived, achieving complete remission after chemo- and radiotherapy. The second patient died of recurrent disease within 5 years of diagnosis. ALDH1A1 was evaluated in both of these cases using an immunohistochemistry scoring system based on the positivity for this marker. The scores were consistent with the patients' clinical outcomes, as the lower (score 1) was observed in the patient with the better clinical outcome, while the higher (score 3) was seen in the patient with the worse outcome.

Conclusion: Our data suggest that ALDH may be an important clinical marker in angiosarcoma of the lung. Although further studies need to be performed in a larger cohort of patients, we believe that, if the results will be confirmed, ALDH1A1 may be used to stratify patients in terms of prognosis and for targeted therapy.

Biological features of tissue and bone sarcomas investigated using an in vitro model of clonal selection

The malignancy progression is an evolutionary process in which tumor clones are selected and competed for the duration of the disease. Intratumor heterogeneity is one of the key problems in the development of treatment methods for cancer patients. In this study we obtained metastatic soft tissue and bone sarcomas (STBSs) cultures from 54 patients, performed in vitro cloning and randomly selected 83 clones. Cloning was successful in 22 cases (40.7%). STBSs cultures with a high clonogenic potential (CP) were characterized by greater proliferative activity and increased Aldehyde dehydrogenase (ALDH) expression. We studied the transcription activity of the following cancer-testis genes (CTG): MAGE, NY-ESO-1, PRAME, GAGE, SSX1, HAGE1, PASD1, SCP1, SEMG1, SLLP1 and SPANXA1. The SEMG1 expression wasn't registered in any studied case. CTG activity wasn't observed in 10 cases out of 52 (19,2%) STBS cultures. We observed CTG activation and increased transcription activity in 82 STBSs clones. Clustering by the gene profile has revealed three different patterns: 1 st - with low expression CTG, 2nd - with co-expression GAGE1, PASD1 and PRAME, 3d - with co-expression SLLP1 and GAGE1. The last two clusters included most cloned cell lines and their clones. CP of STBSs cell lines was associated with the parameters of patients overall survival (OS) at comparable progression-free survival (PFS). Among patients with STBSs with the high CP, median OS was 7.6 months (min 0.7 - max 11.0 months). In the group with the low CP, OS did not reach the median value by the end of the five-year observation period. PFS was 5.6 months (min 0.2 - max 19.2 months) in the first group and 3.2 months (min 0.3- max 71.3 months) in the second group. Resistance to therapeutic doses of chemotherapy drugs was correlated with CP cultures STBSs. We suggest that chemotherapy-resistant clones are pre-existing in the tumor rather than being formed under the influence of chemotherapy. Highly aggressive metastatic sarcomas may be a promising candidate for immunotherapy against cancer-testis antigens (CTAs).

The Role of ALDH in the Metastatic Potential of Osteosarcoma Cells and Potential ALDH Targets

Aldehyde dehydrogenases are a family of enzymes that oxidize aldehydes to carboxylic acids. These enzymes are important in cellular homeostasis during oxidative stress by the elimination of toxic aldehyde by-products from various cellular processes. In osteosarcoma, aldehyde dehydrogenase 1A1has been described as a cancer stem cell marker. Its activity has been found to correlate with metastatic potential and the metastatic phenotype. As such, a more complete understanding of aldehyde dehydrogenase in osteosarcoma will give us a deeper knowledge of its impact on osteosarcoma metastatic potential. Our hope is that this knowledge can be translated into novel antimetastatic therapeutic strategies and thus improve osteosarcoma prognoses.

Repurposing Disulfiram as An Anti-Cancer Agent: Updated Review on Literature and Patents

BACKGROUND

Despite years of success of most anti-cancer drugs, one of the major clinical problems is inherent and acquired resistance to these drugs. Overcoming the drug resistance or developing new drugs would offer promising strategies in cancer treatment. Disulfiram, a drug currently used in the treatment of chronic alcoholism, has been found to have anti-cancer activity.

OBJECTIVE

To summarize the anti-cancer effects of Disulfiram through a thorough patent review.

METHODS

This article reviews molecular mechanisms and recent patents of Disulfiram in cancer therapy.

RESULTS

Several anti-cancer mechanisms of Disulfiram have been proposed, including triggering oxidative stress by the generation of reactive oxygen species, inhibition of the superoxide dismutase activity, suppression of the ubiquitin-proteasome system, and activation of the mitogen-activated protein kinase pathway. In addition, Disulfiram can reverse the resistance to chemotherapeutic drugs by inhibiting the P-glycoprotein multidrug efflux pump and suppressing the activation of NF-kB, both of which play an important role in the development of drug resistance. Furthermore, Disulfiram has been found to reduce angiogenesis because of its metal chelating properties as well as its ability to inactivate Cu/Zn superoxide dismutase and matrix metalloproteinases. Disulfiram has also been shown to inhibit the proteasomes, DNA topoisomerases, DNA methyltransferase, glutathione S-transferase P1, and O6- methylguanine DNA methyltransferase, a DNA repair protein highly expressed in brain tumors. The patents described in this review demonstrate that Disulfiram is useful as an anti-cancer drug.

CONCLUSION

For years the FDA-approved, well-tolerated, inexpensive, orally-administered drug Disulfiram was used in the treatment of chronic alcoholism, but it has recently demonstrated anti-cancer effects in a range of solid and hematological malignancies. Its combination with copper at clinically relevant concentrations might overcome the resistance of many anti-cancer drugs in vitro, in vivo, and in patients.

Prospects for the involvement of cancer stem cells in the pathogenesis of osteosarcoma

Osteosarcoma (OS) is one of the most common bone tumors in children and adolescents that cause a high rate of mortality in this age group and tends to be metastatic, in spite of chemotherapy and surgery. The main reason for this can be returned to a small group of malignant cells called cancer stem cells (CSCs). OS-CSCs play a key role in the resistance to treatment and relapse and metastasis through self-renewal and differentiation abilities. In this review, we intend to go through the different aspects of this malignant disease, including the cancer stem cell-phenotype, methods for isolating CSCs, signaling pathways, and molecular markers in this disease, and drugs showing resistance in treatment efforts of OS.

The Heterogeneity of Osteosarcoma: The Role Played by Cancer Stem Cells

Osteosarcoma is the most common bone sarcoma and is one of the cancer entities characterized by the highest level of heterogeneity in humans. This heterogeneity takes place not only at the macroscopic and microscopic levels, with heterogeneous micro-environmental components, but also at the genomic, transcriptomic and epigenetic levels. Recent investigations have revealed the existence in osteosarcoma of cancer cells with stemness properties. Cancer stem cells are characterized by their specific phenotype and low cycling capacity, and are linked to drug resistance, tumour growth and the metastatic process. In addition, cancer stem cells contribute to the enrichment of tumour heterogeneity. The present manuscript will describe the main characteristic features of cancer stem cells in osteosarcoma and will discuss their impact on maintaining tumour heterogeneity. Their clinical implications will also be briefly addressed.

TRAIL responses are enhanced by nuclear export inhibition in osteosarcoma

Tumour necrosis factor-related apoptosis inducing ligand (TRAIL) is a promising anti-tumour agent that induces apoptosis of malignant cells through activation of death receptors. Death receptor agonistic antibodies are in clinical trials as TRAIL-mimetics, however, along with TRAIL monotherapy, there is limited efficacy due to the rapid emergence of TRAIL resistance, or due to existing TRAIL-insensitive disease. TRAIL-sensitisers, which enhance TRAIL activity or overcome TRAIL resistance, may facilitate death receptor agonists as viable anti-tumour strategies. In this study we demonstrate that the nuclear export inhibitor Leptomycin B, is a potent in vitro TRAIL-sensitiser in osteosarcoma cell lines. Leptomycin B works synergistically with both TRAIL and death receptor 5 agonistic antibodies to induce apoptosis in TRAIL sensitive cell lines. Further, Leptomycin B sensitises TRAIL-insensitive cell lines to TRAIL and death receptor agonistic antibody mediated apoptosis. We also confirmed that aldehyde dehydrogenase (ALDH) positive cells are not resistant to the apoptotic effects of TRAIL and Leptomycin B, an important observation since ALDH positive cells can have enhanced tumorigenicity and are implicated in disease recurrence and metastasis. The nuclear export pathway in combination with death receptor agonists, is a potential therapeutic strategy in osteosarcoma and warrants further research on clinically relevant selective inhibitors of nuclear export.

Combination Therapy with Disulfiram, Copper, and Doxorubicin for Osteosarcoma: In Vitro Support for a Novel Drug Repurposing Strategy

Although many cancer cells have significantly higher copper concentrations compared with normal cells and tissues, the role of copper in cancer biology and metastatic disease remains poorly understood. Here, we study the importance of copper in osteosarcoma, which frequently metastasizes to the lungs and is often chemoresistant. K12 and K7M2 are murine OS cells with differing metastatic phenotypes: K7M2 is highly metastatic, whereas K12 is much less so. Intracellular copper levels were determined using atomic absorption. Copper transporters were quantified by qPCR. Cytotoxicity of doxorubicin, disulfiram, and copper(II) chloride was assessed with a cell viability fluorescence stain. Additionally, K7M2 viable cell counts were determined by trypan blue exclusion staining after 72 hours of treatment. Copper levels were found to be significantly higher in K12 OS cells than in K7M2 cells. qPCR showed that K12 cells upregulate the copper influx pump CTR1 and downregulate the copper efflux pump ATP7A compared to K7M2 OS cells. Combination treatment of copper chloride (50 nM) with disulfiram (80 nM) was only cytotoxic to K12 cells. Triple treatment with doxorubicin, disulfiram, and copper displayed potent and durable cytotoxicity of highly metastatic K7M2 cells. We demonstrate here that murine OS cell lines differing in metastatic potential also vary in endogenous copper levels and regulation. Additionally, these differences in copper regulation may contribute to selective cytotoxicity of K12 cells by extremely low doses of copper-potentiated disulfiram. The combination of doxorubicin, disulfiram, and copper should be explored as a therapeutic strategy against OS metastases.

PRP‑1 significantly decreases the ALDHhigh cancer stem cell population and regulates the aberrant Wnt/β‑catenin pathway in human chondrosarcoma JJ012 cells

Chondrosarcomas are malignant bone tumors refractory to chemotherapy and radiation treatment; thus, novel therapeutic strategies are required. Proline-rich polypeptide 1 (PRP-1) has previously demonstrated antitumor properties in chondrosarcoma. To further investigate the role of PRP-1 in chondrosarcoma cells, its effects on cancer stem cell (CSC) populations were determined by analyzing aldehyde dehydrogenase (ALDH) activity, an established marker of CSCs, in association with regulation of the Wnt/β-catenin signaling. A significant decrease in ALDH^high CSCs was observed following treatment of chondrosarcoma JJ012 cells with PRP-1. For RT² profiler PCR array analysis of Wnt/β-catenin signaling genes, cells were sorted into: i) Bulk JJ012 cells; ii) ALDH^high cells sorted from untreated JJ012 cells (ALDH^{high-untreated}); and iii) ALDH^low cells sorted from PRP-1-treated JJ012 cells (ALDH^low-PRP-1). The expression levels of Wnt/β-catenin signaling genes were determined to be downregulated in the ALDH^{high-untreated} cells and upregulated in ALDH^low-PRP-1 cells when compared to the bulk JJ012 cells. Additionally, two important oncogenes involved in this pathway, MMP7 and CCND2, were found to be downregulated in the ALDH^low-PRP-1 cells. Immunocytochemistry demonstrated the localization of β-catenin in the nuclei of the PRP-1-treated cells. Western blotting indicated increased β-catenin expression in the ALDH^low-PRP-1 cells compared with the bulk JJ012 cells. Analysis of the cytoplasmic and nuclear fractions of cells treated with increasing concentrations of PRP-1 and β-catenin nuclear translocation inhibitor CGP57380, suggested the nuclear translocation of β-catenin following PRP-1 treatment. In addition, treatment of JJ012 cells with a specific ALDH inhibitor, diethylaminobenzaldehyde, and PRP-1 resulted in a significant decrease in cytoplasmic β-catenin protein expression. This indicated that ALDH inactivation may be associated with the nuclear translocation of β-catenin. Derivation of sarcomas from mesenchymal stem cells via inactivation of the Wnt pathway has been previously documented. The findings of the present study support the notion that Wnt/β-catenin activation may serve a differential role in sarcomas, limiting tumor progression in association with decreased CSC activity.

A phase II study of temsirolimus and liposomal doxorubicin for patients with recurrent and refractory bone and soft tissue sarcomas

Background

Relapsed and refractory sarcomas continue to have poor survival rates. The cancer stem cell (CSC) theory provides a tractable explanation for the observation that recurrences occur despite dramatic responses to upfront chemotherapy. Preclinical studies demonstrated that inhibition of the mechanistic target of rapamycin (mTOR) sensitizes the CSC population to chemotherapy.

Methods

Here we present the results of the Phase II portion of a Phase I/II clinical trial that aimed to overcome the chemoresistance of sarcoma CSC by combining the mTOR inhibitor temsirolimus (20 mg/m² weekly) with the chemotherapeutic agent liposomal doxorubicin (30 mg/m² monthly).

Results

Fifteen patients with relapsed/refractory sarcoma were evaluable at this recommended Phase 2 dose level. The median progression free survival was 315 days (range 27–799). Response rate, defined as stable disease or better for 60 days, was 53%. Nine of the patients had been previously treated with doxorubicin. Therapy was well tolerated. In a small number of patients, pre- and post- treatment tumor biopsies were available for assessment of ALDH expression as a marker of CSCs and showed a correlation between response and decreased ALDH expression. We also found a correlation between biopsy-proven inhibition of mTOR and response.

Conclusions

Our study adds to the literature supporting the addition of mTOR inhibition to chemotherapy agents for the treatment of sarcomas, and proposes that a mechanism by which mTOR inhibition enhances the efficacy of chemotherapy may be through sensitizing the chemoresistant CSC population. Further study, ideally with pre- and post-therapy assessment of ALDH expression in tumor cells, is warranted.

Trial registration The trial was registered on clinicaltrials.gov (NCT00949325) on 30 July 2009. http://www.editorialmanager.com/csrj/default.aspx

Novel molecular insights and new therapeutic strategies in osteosarcoma

Osteosarcoma (OS) is one of the most prevalent malignant cancers with lower survival and poor overall prognosis mainly in children and adolescents. Identifying the molecular mechanisms and OS stem cells (OSCs) as new concepts involved in disease pathogenesis and progression may potentially lead to new therapeutic targets. Therefore, therapeutic targeting of OSCs can be one of the most important and effective strategies for the treatment of OS. This review describes the new molecular targets of OS as well as novel therapeutic approaches in the design of future investigations and treatment.

Disulfiram reduces metastatic osteosarcoma tumor burden in an immunocompetent Balb/c or-thotopic mouse model

Introduction

The overall survival rate of patients with osteosarcoma (OS) and pulmonary metastases has remained stagnant at 15–30% for several decades. Disulfiram (DSF) is an FDA-approved aldehyde dehydrogenase inhibitor that reduces the metastatic phenotype of OS cells in vitro. Here we evaluate its in vivo efficacy, as compared to doxorubicin chemotherapy, in a previously-validated orthotopic model of metastatic OS.

Results

All treatment groups displayed a significantly reduced quantitative OS metastatic burden compared with controls. The metastatic burden of Lo DSF-treated animals was equivalent to the DXR group. Ninety-five percent of control animals displayed evidence of metastatic disease, which was significantly greater than all treatment groups.

Discussion

Disulfiram treatment resulted in a reduced burden of OS metastatic disease compared with controls. This was statistically-equivalent to doxorubicin. No additive effect was observed between these two therapies.

Materials and Methods

One-hundred twenty immunocompetent Balb/c mice received proximal tibia paraphyseal injections of 5 × 10⁵ K7M2 murine OS cells. Therapy began three weeks after injection: saline (control), low-dose disulfiram (Lo DSF), high-dose disulfiram (Hi DSF), doxorubicin (DXR), Lo DSF + DXR, and Hi DSF + DXR. Transfemoral amputations were performed at 4 weeks. Quantitative metastatic tumor burden was measured using near-infrared indocyanine green (ICG) angiography.

Pediatric sarcomas

Sarcomas arise from primitive mesenchymal cells, which are classified, into two main groups: Bone and soft tissue sarcomas. We have searched all-important electronic databases including Google scholar and PubMed for the collection of latest literature pertaining to pediatric sarcomas. Latest literature confirmed that these tumors are relatively rare and represent only 1% of all malignancies but they have higher incidence in children. Pediatric sarcomas comprise about 13% of all pediatric malignancies and are ranked third in childhood cancers. The highest incidence rates are reported among rhabdomyosarcoma, osteosarcoma and Ewing's sarcomas in children. All of these neoplasms often display highly aggressive behavior with tendency to form metastases. Important globally used management avenues include surgery with systemic chemotherapy and have success rate of 70% at 5-years. Furthermore, in the cases of advanced stages, the prognosis is poor, chances of treatment failure and recurrence are quite high. Utilization of cancer stem cells is the latest approach with great potential in management of above pathological state. The present review article discuss all-important aspects of commonly found pediatric sarcomas throughout the world.

Alcohol Dehydrogenases and Acetaldehyde Dehydrogenases are Beneficial for Decidual Stromal Cells to Resist the Damage from Alcohol

Aims

The aim of this study was to examine the effect of alcohol on the decidualization of human endometrial stromal cells during early pregnancy.

Methods

During in vitro decidualization, human endometrial stromal cells were treated with alcohol, 4-methylpyrazole hydrochloride (FPZ), the inhibitor of alcohol dehydrogenases (ADHs), and tetraethylthiuram disulfide (DSF), the inhibitor of acetaldehyde dehydrogenases (ALDHs), respectively. Cell viability and decidualization were examined. Apoptosis and proliferation were also evaluated.

Results

The findings showed that ADHs and ALDHs were up-regulated during decidualization. After alcohol treatment, the cell viability of decidual stromal cells was significantly higher than control, which was abrogated by FPZ or DSF. When cells were treated with alcohol, proliferation-related signal pathways were up-regulated in decidualized cells. Additionally, FOXO1 transcriptionally up-regulates ADH1B.

Conclusion

Our study provided an evidence that highly expressed ADHs and ALDHs endow decidual stromal cells an ability to alleviate the harm from alcohol.

[Lymph node metastasis of osteosarcomas]

Lymph node metastasis of osteosarcomas is a rather rare phenomenon; according to different authors, the incidence of lymph node metastasis is 4 to 11%. The detection of lymph node metastases in osteosarcoma is associated with a significant reduction in the 5-year survival of patients and allows its classification as clinical stage IV tumor. The risk factors for lymph node metastases in patients with bone sarcomas are age (≥64 years), gender (female), nosological entity (undifferentiated pleomorphic sarcoma, osteosarcoma, chondrosarcoma), tumor depth (muscle, bone), and the size of primary tumor (>5 сm). The mechanism of lymph node metastasis of osteosarcomas seems to be related to mesenchymal-to-epithelial transition.

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.

Cancer stem cells in osteosarcoma

Osteosarcoma is the most common primary bone tumour in children and adolescents and advanced osteosarcoma patients with evidence of metastasis share a poor prognosis. Osteosarcoma frequently gains resistance to standard therapies highlighting the need for improved treatment regimens and identification of novel therapeutic targets. Cancer stem cells (CSC) represent a sub-type of tumour cells attributed to critical steps in cancer including tumour propagation, therapy resistance, recurrence and in some cases metastasis. Recent published work demonstrates evidence of cancer stem cell phenotypes in osteosarcoma with links to drug resistance and tumorigenesis. In this review we will discuss the commonly used isolation techniques for cancer stem cells in osteosarcoma as well as the identified biochemical and molecular markers.

The Challenges of Detecting Circulating Tumor Cells in Sarcoma

Sarcomas are a heterogeneous group of malignant neoplasms of mesenchymal origin, many of which have a propensity to develop distant metastases. Cancer cells that have escaped from the primary tumor are able to invade into surrounding tissues, to intravasate into the bloodstream to become circulating tumor cells (CTCs), and are responsible for the generation of distant metastases. Due to the rarity of these tumors and the absence of specific markers expressed by sarcoma tumor cells, the characterization of sarcoma CTCs has to date been relatively limited. Current techniques for isolating sarcoma CTCs are based on size criteria, the identification of circulating cells that express either common mesenchymal markers, sarcoma-specific markers, such as CD99, CD81, or PAX3, and chromosomal translocations found in certain sarcoma subtypes, such as EWS-FLI1 in Ewing’s sarcoma, detection of osteoblast-related genes, or measurement of the activity of specific metabolic enzymes. Further studies are needed to improve the isolation and characterization of sarcoma CTCs, to demonstrate their clinical significance as predictive and/or prognostic biomarkers, and to utilize CTCs as a tool for investigating the metastatic process in sarcoma and to identify novel therapeutic targets. The present review provides a short overview of the most recent literature on CTCs in sarcoma.

Same difference: A pilot study of cyclin D1, bcl-2, AMACR, and ALDH-1 identifies significant differences in expression between primary colon adenocarcinoma and its metastases

Tumor heterogeneity implies the possibility of significantly different expression of key pathways between primary and metastatic clones. Colon adenocarcinoma is one of the few tumors where current practice includes resection of primary and isolated organ metastases simultaneously without neoadjuvant therapy. We performed a pilot study on 28 cases of colon adenocarcinoma resected simultaneously with metastases in patients with no history of neoadjuvant therapy. We assayed matched primary and metastatic tumors from each patient with common diagnostic antibodies to Bcl-2, Cyclin D1, AMACR, and ALDH-1 by immunohistochemistry with semi-quantitative interpretation on archived formalin fixed, paraffin embedded samples. We were powered for large, consistent differences between primary and metastatic expression, and found 21 of 28 had a significant difference in expression of at least one of the four proteins, accounting for multiplicity of testing. Cyclin D1 had significantly more cases with differential metastatic:primary expression than would be expected by chance alone (p-value 0.0043), favoring higher expression in the metastatic sample. Bcl-2 and ALDH-1 had trends in this direction (p-value 0.078 each). Proportionately more cases with significant differences were identified when a liver metastasis was tested. We conclude differences in expression between metastatic and primary colon adenocarcinoma within the same patient exist, and may have therapeutic and biomarker testing consequences.

Aldh1 Expression and Activity Increase During Tumor Evolution in Sarcoma Cancer Stem Cell Populations

Tumors evolve from initial tumorigenic events into increasingly aggressive behaviors in a process usually driven by subpopulations of cancer stem cells (CSCs). Mesenchymal stromal/stem cells (MSCs) may act as the cell-of-origin for sarcomas, and CSCs that present MSC features have been identified in sarcomas due to their ability to grow as self-renewed floating spheres (tumorspheres). Accordingly, we previously developed sarcoma models using human MSCs transformed with relevant oncogenic events. To study the evolution/emergence of CSC subpopulations during tumor progression, we compared the tumorigenic properties of bulk adherent cultures and tumorsphere-forming subpopulations both in the sarcoma cell-of-origin models (transformed MSCs) and in their corresponding tumor xenograft-derived cells. Tumor formation assays showed that the tumorsphere cultures from xenograft-derived cells, but not from the cell-of-origin models, were enriched in CSCs, providing evidence of the emergence of bona fide CSCs subpopulations during tumor progression. Relevant CSC-related factors, such as ALDH1 and SOX2, were increasingly upregulated in CSCs during tumor progression, and importantly, the increased levels and activity of ALDH1 in these subpopulations were associated with enhanced tumorigenicity. In addition to being a CSC marker, our findings indicate that ALDH1 could also be useful for tracking the malignant potential of CSC subpopulations during sarcoma evolution.

Concise review: bullseye: targeting cancer stem cells to improve the treatment of gliomas by repurposing disulfiram

Cancer stem cells (CSCs) are thought to be at the root of cancer recurrence because they resist conventional therapies and subsequently reinitiate tumor cell growth. Thus, targeting CSCs could be the bullseye to successful cancer therapeutics in the future. Brain tumors are some of the most challenging types of cancer to treat and the median survival following the initial diagnosis is 12-18 months. Among the different types of brain tumors, glioblastoma (GBM) is considered the most aggressive and remains extremely difficult to treat. Despite surgery, radiation, and chemotherapy, most patients develop refractory disease. Temozolomide (TMZ) is a chemotherapy used to treat GBM however resistance develops in most patients. The underlying mechanisms for TMZ resistance (TMZ-resistant) involve the expression of DNA repair gene O(6)-methylguanine-DNA methyltransferase. CSC genes such as Sox-2, BMI-1, and more recently Y-box binding protein-1 also play a role in resistance. In order to develop novel therapies for GBM, libraries of small interfering RNAs and off-patent drugs have been screened. Over the past few years, several independent laboratories identified disulfiram (DSF) as an off-patent drug that kills GBM CSCs. Reportedly DSF has several modes of action including its ability to inhibit aldehyde dehydrogenases, E3 ligase, polo-like kinase 1, and NFkB. Due to the fact that GBM is a disease of heterogeneity, chemotherapy with multitargeting properties may be the way of the future. In broader terms, DSF kills CSCs from a range of different cancer types further supporting the idea of repurposing it for "target practice."

Retinal Targets ALDH Positive Cancer Stem Cell and Alters the Phenotype of Highly Metastatic Osteosarcoma Cells

Aldehyde dehydrogenase (ALDH) is a cancer stem cell marker. Retinoic acid has antitumor properties, including the induction of apoptosis and inhibition of proliferation. Retinal, the precursor of retinoic acid, can be oxidized to retinoic acid by dehydrogenases, including ALDH. We hypothesized that retinal could potentially be transformed to retinoic acid with higher efficiency by cancer stem cells, due to the higher ALDH activity. We previously observed that ALDH activity is greater in highly metastatic K7M2 osteosarcoma (OS) cells than in nonmetastatic K12 OS cells. We also demonstrated that ALDH activity correlates with clinical metastases in bone sarcoma patients, suggesting that ALDH may be a therapeutic target specific to cells with high metastatic potential. Our current results demonstrated that retinal preferentially affected the phenotypes of ALDH-high K7M2 cells in contrast to ALDH-low K12 cells, which could be mediated by the more efficient transformation of retinal to retinoic acid by ALDH in K7M2 cells. Retinal treatment of highly metastatic K7M2 cells decreased their proliferation, invasion capacity, and resistance to oxidative stress. Retinal altered the expression of metastasis-related genes. These observations indicate that retinal may be used to specifically target metastatic cancer stem cells in OS.

Aldehyde dehydrogenase as a marker and functional mediator of metastasis in solid tumors

There is accumulating evidence indicating that aldehyde dehydrogenase (ALDH) activity selects for cancer cells with increased aggressiveness, capacity for sustained proliferation, and plasticity in primary tumors. However, emerging data also suggests an important mechanistic role for the ALDH family of isoenzymes in the metastatic activity of tumor cells. Recent studies indicate that ALDH correlates with either increased or decreased metastatic capacity in a cellular context-dependent manner. Importantly, it appears that different ALDH isoforms support increased metastatic capacity in different tumor types. This review assesses the potential of ALDH as biological marker and mechanistic mediator of metastasis in solid tumors. In many malignancies, most notably in breast cancer, ALDH activity and expression appears to be a promising marker and potential therapeutic target for treating metastasis in the clinical setting.

The HDAC inhibitor Vorinostat diminishes the in vitro metastatic behavior of Osteosarcoma cells

Osteosarcoma (OS) is the most common primary malignancy of bone and affects patients in the first two decades of life. The greatest determinant of survival is the presence of pulmonary metastatic disease. The role of epigenetic regulation in OS, specifically the biology of metastases, is unknown. Our previous study with the murine OS cell populations K7M2 and K12 demonstrated a significant correlation of metastatic potential with the DNA methylation level of tumor suppressor genes. In the current study, we investigated if the histone deacetylase (HDAC) inhibitor, vorinostat, could regulate the metastatic potential of highly metastatic OS cells. Our results revealed that vorinostat treatment of highly metastatic K7M2 OS cells was able to greatly reduce the proliferation and metastatic potential of the cells. Morphological features related to cell motility and invasion were changed by vorinostat treatment. In addition, the gene expressions of mTOR, ALDH1, and PGC-1 were downregulated by vorinostat treatment. These data suggest that vorinostat may be an effective modulator of OS cell metastatic potential and should be studied in preclinical models of metastatic OS.