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Telomerase therapeutics for cancer: challenges and new directions.

It has been approximately a decade since telomerase was described as an almost universal marker for human cancer. Most human tumours not only express telomerase but also have very short telomeres, whereas telomerase activity is either reduced or absent in normal tissues, making the inhibition of telomerase an attractive target for cancer therapeutics. Here we review the current status of telomerase therapeutics and discuss future opportunities and challenges for telomerase research, including a possible relationship with cancer stem cells that could be a source of chemo-/radioresistance development in many advanced cancers.

Animals↗

Hetero-duplication type of cancerous mitosis.

In normal mitosis, the two daughter cells are identical to each other. However, in the case of duplication mitosis of the non-matureable cancerous stem cell, the two daughter stem cells must be non-visually, but certainly different from each other in order to allow for the characteristic type of cancerous cell turnover development. One of these daughter stem cells is matureable and normally activated by the maturation factor, then undergoes maturation mitosis and finally passes through its lifespan. However, the other daughter stem cell is non-matureable and not activated by the maturation factor. It undergoes the original mitosis again, reproducing two daughter stem cells that differ from each other: te above matureable cell and the original non-matureable cell (Fig.). Such a hetero-duplication type of mitosis is peculiar to carcinoma and responsible for the oncogenesis. The origin of this mitosis is most probably an unequal division of a mitotic maturation promoting system (MMPS) at the mitotic phase, and may be dependent on some abnormal supplement of the MMPS. Thus, therapy aimed at the complete eradication of cancer should focus on removal of this supplement from the cancerous cell.

Animals↗

Treating cancer with embryonic stem cells: rationale comes from aging studies.

In an earlier poster paper (1) we proposed that cancer can be viewed not only as a fatal disease but also as a local aberrant, rejuvenation, in an organism, and this fact can be useful for developing new anti-aging and anti-cancer treatments. In this paper we provide additional evidence from human and experimental animal studies in support of this view. First, we discuss cancer genes as candidate targets for anti-aging interventions. We review examples in which the life of experimental animals has been prolonged in situations of increased activity of proto-oncogenes - or decreased activity of tumor suppressors - in normal (non-cancerous) cells in vivo. Studies of genetic polymorphisms revealed similar effects on longevity in humans. Second, we discuss the possibility of treating cancer with embryonic stem cells. The fact that cancer cells do not, age, means that these cells overcome aging host cells. However, cancer cells can be suppressed by young and quickly proliferating non-cancer cells, such as embryonic stem cells. The grafting of these cells in the tumor environment could be a prospective non-toxic anti-cancer treatment. We discuss recent evidence in support of this view.

Animals↗

Perspectives and controversies in the field of stem cell research.

The fourth annual meeting of the International Society for Stem Cell Research focused on a number of pressing issues, including: (I) the need to better characterize the biology of stem cells; (II) the need to exploit and optimize the great therapeutic potential of stem cells in tissue regeneration; (III) ethical and safety considerations related to the use of human embryonic stem cells; (IV) the contribution of adult stem cells to carcinogenesis; (V) the need to investigate the biology of cancer stem cells. The purpose of this report is to summarize the current status of stem cell research, as surmised by the proceedings of this meeting.

Adult↗

NOTCH1 acts as a tumor suppressor that induces early differentiation in head and neck cancer.

Inactivating NOTCH1 mutations in head and neck squamous cell carcinoma (HNSCC) were described over a decade ago, suggesting a tumor suppressor function - unlike its oncogenic role in other tumors. Today, much debate persists regarding a putative oncogenic role in HNSCC as well, with reports that NOTCH1 signaling drives tumor growth and a cancer stem cell (CSC) phenotype. In this work, comprehensive experiments unequivocally demonstrate that NOTCH1 is a tumor suppressor in HNSCC regardless of mutation or activation status and that it reduces CSC frequency. We developed a signature of NOTCH1 activation showing the pathway is associated with very early differentiation, an altered tumor microenvironment, and better prognosis. Clarifying whether NOTCH1 occasionally functions as an oncogenic driver in HNSCC is crucial to prognosis and personalized therapy. The results presented unify the field, reconcile conflicting data, and provide critical insights into the biological and clinical significance of NOTCH1, with broader implications in other squamous carcinomas with NOTCH1 mutations.

Receptor, Notch1↗

Leukemic stem cells: where do they come from?

Leukemias can now be viewed as aberrant hematopoietic processes initiated by rare cancer stem cells, or leukemic stem cells (LSCs) that have maintained or reacquired the capacity for indefinite proliferation through accumulated mutations and/or epigenetic changes. Yet, despite their critical importance, much remains to be learned about the developmental origin of LSCs and the mechanisms responsible for their emergence in the course of the disease. Mouse models of human leukemias have provided a unique system to study the mechanisms influencing LSC generation and function, and were recently used to demonstrate that LSCs can arise from both self-renewing hematopoietic stem cells (HSCs) and committed progenitor populations. This striking finding indicates that LSC identity is largely dictated by the nature of the oncogenic events and by how these events perturb essential processes such as self-renewal, proliferation, differentiation, and survival. Such approaches in the mouse are essential for the basic understanding of leukemogenesis and for the conceptual design of novel therapeutic strategies that could lead to improved treatments for human leukemias.

Animals↗

Why therapeutic response may not prolong the life of a cancer patient: selection for oncogenic resistance.

Most cancers do not respond to chemotherapy. Disappointedly, even objective clinical responses to anticancer therapy often do not translate into improvements in overall survival. To explain the response-survival paradox, it has been pointed out that effective therapy is ineffective against cancer stem cells, which replenish the tumor (causing relapse). In contrast, I discuss that, according to this scenario, patient survival will be prolonged at least by the duration of remission. Furthermore, stem-cell-based relapses will be sensitive to the initial therapy, and in theory cancer could be controlled indefinitely. To explain the paradox, I discuss that effective therapy selects for resistance among proliferating cancer cells. Importantly, mechanisms of resistance can be divided into nononcogenic (e.g., drug transporters and mutation in drug-targets) and oncogenic (e.g., apoptosis avoidance and cell cycle dysregulation). Oncogenic resistance is associated with highly aggressive cancer phenotype and, therefore, there is no increase in overall survival. I further suggest that (a) therapeutic response is a prerequisite for successful therapy, (b) resistance can be exploited for therapeutic advantage, (c) each response can be translated into increased survival, and (e) in slow growing tumors, cancer can be stopped without tumor shrinkage. Therapy will control cancer if it can selectively suppress proliferating cancer cells and will improve survival as long as acquired resistance can be exploited.

Cell Proliferation↗

Markers of adult tissue-based stem cells.

The expectation generated by the pluripotentiality of embryonic stem (ES) cells has initiated a renaissance in stem cell biology. While ES cells can be harvested in abundance and appear to be the most versatile of cells for regenerative medicine, adult stem cells also hold promise, but the identity and subsequent isolation of these comparatively rare cells remains problematic in most tissues, perhaps with the notable exception of the bone marrow. Identifying surface molecules (markers) that would aid in stem cell isolation is thus a major goal for stem cell biologists. Moreover, the characterization of normal stem cells in specific tissues may provide a dividend for the treatment of cancer. There is a growing belief that the successful treatment of neoplastic disease will require specific targeting of the cancer stem cells, cells that may well have many of the characteristics of their normal counterparts.

Adult↗

Molecular signatures of proliferation and quiescence in hematopoietic stem cells.

Stem cells resident in adult tissues are principally quiescent, yet harbor enormous capacity for proliferation to achieve self renewal and to replenish their tissue constituents. Although a single hematopoietic stem cell (HSC) can generate sufficient primitive progeny to repopulate many recipients, little is known about the molecular mechanisms that maintain their potency or regulate their self renewal. Here we have examined the gene expression changes that occur over a time course when HSCs are induced to proliferate and return to quiescence in vivo. These data were compared to data representing differences between naturally proliferating fetal HSCs and their quiescent adult counterparts. Bioinformatic strategies were used to group time-ordered gene expression profiles generated from microarrays into signatures of quiescent and dividing stem cells. A novel method for calculating statistically significant enrichments in Gene Ontology groupings for our gene lists revealed elemental subgroups within the signatures that underlie HSC behavior, and allowed us to build a molecular model of the HSC activation cycle. Initially, quiescent HSCs evince a state of readiness. The proliferative signal induces a preparative state, which is followed by active proliferation divisible into early and late phases. Re-induction of quiescence involves changes in migratory molecule expression, prior to reestablishment of homeostasis. We also identified two genes that increase in both gene and protein expression during activation, and potentially represent new markers for proliferating stem cells. These data will be of use in attempts to recapitulate the HSC self renewal process for therapeutic expansion of stem cells, and our model may correlate with acquisition of self renewal characteristics by cancer stem cells.

Analysis of Variance↗

On mammary stem cells.

Mammary gland stem cells are a quiescent and self-renewing population within the mammary gland that are capable of giving rise to the differentiated ductal, alveolar and myoepithelial cells. To identify mammary gland stem cells, several investigators have employed a variety of methods including: non-adherent mammosphere cultures; 5-bromo-2-deoxy-uridine (BrdU) label-retention studies; cell-surface markers, such as Sca1 and CD49f; and Hoechst dye efflux. These methods have helped identify and further characterize signal transduction pathways such as the Notch, Wnt and Hedgehog pathways that may be important for the self-renewal and fate determination of mammary gland stem cells. Stem cells within the mammary gland have been proposed to underpin many types of breast cancer. A better understanding of the signal transduction pathways and the molecules that are responsible for the self-renewal and survival of these cells will be essential in the design of more effective therapies aimed at the eradication of both cancer-initiating cells and breast cancer stem cells.

Animals↗

Expression of hiwi gene in human gastric cancer was associated with proliferation of cancer cells.

Stem cell genetics research may be critical to our understanding of carcinogenesis, as both stem cells and cancer cells possess the ability to self-renew. Recent discoveries have indicated that the piwi family of genes plays an essential role in stem cell self-renewal in diverse organisms. The hiwi gene, the human homolog of the piwi family, participates in germ cell proliferation and its overexpression may cause the development of germ cell malignancy, but its expression and function in epithelial solid cancers have not been explored. In the present study, we investigated whether there was an association between hiwi expression and human gastric cancer and its potential mechanism. RT-PCR findings demonstrated that hiwi was expressed in different gastric cancer cell lines. To identify the HIWI protein in gastric cancer, we developed a specific monoclonal antibody against HIWI and immunohistochemistry was performed on various gastric tissues. We found that the expression ratio of hiwi in normal gastric tissues, atrophic gastritis, intestinal metaplasia and gastric cancers was 10% (5/50), 36% (18/50), 36% (18/50) and 76% (38/50), respectively, which was consistent with precancerous development. Notably, the expression pattern of hiwi in gastric cancer tissues was similar to that of Ki67, which was used as a marker of proliferation. Moreover, the suppression of hiwi by antisense or RNAi inhibited the growth of gastric cancer cells and induced cell cycle arrest in G2/M phase. These results suggest that hiwi may be involved in the development of gastric cancer and is a potential target for cancer therapy.

Antibodies, Monoclonal↗

Identification of human brain tumour initiating cells.

The cancer stem cell (CSC) hypothesis suggests that neoplastic clones are maintained exclusively by a rare fraction of cells with stem cell properties. Although the existence of CSCs in human leukaemia is established, little evidence exists for CSCs in solid tumours, except for breast cancer. Recently, we prospectively isolated a CD133+ cell subpopulation from human brain tumours that exhibited stem cell properties in vitro. However, the true measures of CSCs are their capacity for self renewal and exact recapitulation of the original tumour. Here we report the development of a xenograft assay that identified human brain tumour initiating cells that initiate tumours in vivo. Only the CD133+ brain tumour fraction contains cells that are capable of tumour initiation in NOD-SCID (non-obese diabetic, severe combined immunodeficient) mouse brains. Injection of as few as 100 CD133+ cells produced a tumour that could be serially transplanted and was a phenocopy of the patient's original tumour, whereas injection of 10(5) CD133- cells engrafted but did not cause a tumour. Thus, the identification of brain tumour initiating cells provides insights into human brain tumour pathogenesis, giving strong support for the CSC hypothesis as the basis for many solid tumours, and establishes a previously unidentified cellular target for more effective cancer therapies.

AC133 Antigen↗

Treatment of locally advanced prostate cancer: is chemotherapy the next step?

PURPOSE: Management of locally advanced prostate cancer remains controversial. Various single and combination modality approaches have been advocated, but an accepted standard of care remains undefined. The purpose of this review is to define the current knowledge in managing locally advanced prostate cancer and to propose new treatment approaches based on current knowledge. MATERIALS AND METHODS: A MEDLINE search to detect all relevant articles on the management of locally advanced prostate cancer was performed. A review of the staging, natural history, and prognosis of this disease was also performed. RESULTS: The lack of a clearly defined treatment approach to patients with locally advanced prostate cancer stems from multiple factors, including ambiguities in clinical staging, inadequate knowledge of the natural history of the cancer, and a dearth of comparative randomized trials evaluating efficacy of different therapies. Single modality treatment, including radical prostatectomy (RP) or external-beam radiotherapy alone, is associated with high rates of failure. The use of adjuvant hormonal ablation therapy in combination with external-beam radiotherapy has shown improvement in progression-free and overall survival, although similar improvements have not been clearly demonstrated for surgical patients treated with hormonal therapy. New advances in chemotherapy for hormone-refractory prostate cancer suggest that response rates may be as high as 50% or more, and current trials are evaluating the addition of chemotherapy to hormonal ablation in either surgery or radiation therapy in locally advanced prostate cancer. CONCLUSION: Optimal management of locally advanced prostate cancer remains undefined. Standard treatment options include RP, external-beam radiotherapy, or hormonal ablation therapy, alone or in combination. New approaches being tested include improved methods for delivering radiation or combining hormonal ablation with surgery or radiation. It is possible that other forms of systemic therapy, including chemotherapy, may become important components of multimodality treatment. Clinical trials designed to test this hypothesis are ongoing.

Actuarial Analysis↗

Potential role of NF-kappaB in adult neural stem cells: the underrated steersman?

Neural stem cells are precursors of neurons and glial cells. During brain development, these cells proliferate, migrate and differentiate into specific lineages. Recently neural stem cells within the adult central nervous system were identified. Informations are now emerging about regulation of stem cell proliferation, migration and differentiation by numerous soluble factors such as chemokines and cytokines. However, the signal transduction mechanisms downstream of these factors are less clear. Here, we review potential evidences for a novel central role of the transcription factor nuclear factor kappa B (NF-kappaB) in these crucial signal transduction processes. NF-kappaB is an inducible transcription factor detected in neurons, glia and neural stem cells. NF-kappaB was discovered by David Baltimore's laboratory as a transcription factor in lymphocytes. NF-kappaB is involved in many biological processes such as inflammation and innate immunity, development, apoptosis and anti-apoptosis. It has been recently shown that members of the NF-kappaB family are widely expressed by neurons, glia and neural stem cells. In the nervous system, NF-kappaB plays a crucial role in neuronal plasticity, learning, memory consolidation, neuroprotection and neurodegeneration. Recent data suggest an important role of NF-kappaB on proliferation, migration and differentiation of neural stem cells. NF-kappaB is composed of three subunits: two DNA-binding and one inhibitory subunit. Activation of NF-kappaB takes place in the cytoplasm and results in degradation of the inhibitory subunit, thus enabling the nuclear import of the DNA-binding subunits. Within the nucleus, several target genes could be activated. In this review, we suggest a model explaining the multiple action of NF-kappaB on neural stem cells. Furthermore, we discuss the potential role of NF-kappaB within the so-called brain cancer stem cells.

Animals↗

The role of LMO2 in development and in T cell leukemia after chromosomal translocation or retroviral insertion.

Chromosomal translocations are primary events in the development of leukemias, representing at least one genetic feature of the putative cancer stem cell. Studies of genes influenced by chromosomal translocations have yielded a vast amount of information about how cancer is initiated and maintained. In particular, acute leukemias have demonstrated that chromosomal translocations often involve transcription regulators that function by interacting with proteins and by controlling cell fate in the aberrant setting of the developing cancer cell. As a quintessential chromosomal translocation gene product, LMO2 has many properties that typify this class of molecule. In addition to its involvement in chromosomal translocations, the LMO2 gene was inadvertently activated in an X-SCID gene therapy trial by retroviral insertion. New molecular therapies targeted directly at the LMO2 protein could have major impact as adjuncts to existing therapies or as therapeutics in their own right. In this review, we outline the current knowledge about LMO2 and some possible routes to develop reagents that might be possible macromolecular drugs in the future.

Adaptor Proteins, Signal Transducing↗

Community cancer assessment in response to long-time exposure to perchlorate and trichloroethylene in drinking water.

In response to concerns about cancer stemming from drinking water contaminated with ammonium perchlorate and trichloroethylene, we assessed observed and expected numbers of new cancer cases for all sites combined and 16 cancer types in a California community (1988 to 1998). The numbers of observed cancer cases divided by expected numbers defined standardized incidence ratios (SIRs) and 99% confidence intervals (CI). No significant differences between observed and expected numbers were found for all cancers (SIR, 0.97; 99% CI, 0.93 to 1.02), thyroid cancer (SIR, 1.00; 99% CI, 0.63 to 1.47), or 11 other cancer types. Significantly fewer cases were observed than expected for cancer of the lung and bronchus (SIR, 0.71; 99% CI, 0.61 to 0.81) and the colon and rectum (SIR, 0.86; 0.74 to 0.99), whereas more cases were observed for uterine cancer (SIR, 1.35; 99% CI, 1.06 to 1.70) and skin melanoma (SIR, 1.42; 99% CI, 1.13 to 1.77). These findings did not identify a generalized cancer excess or thyroid cancer excess in this community.

Adult↗

Decoding glioblastoma evolution and heterogeneity through mechanistic modeling: implications for clinical translation.

Glioblastoma (GBM) is one of the most aggressive and lethal primary brain tumors in adults, characterized by dynamic clonal evolution and extensive genomic, cellular, spatial, and microenvironmental heterogeneity. Multi-omics studies have revealed that GBM follows complex evolutionary trajectories involving genetic, epigenetic, transcriptional, and immune-microenvironmental remodeling as tumors grow, adapt to the brain microenvironment, and acquire therapeutic resistance. Increasing evidence suggests that GBM may originate from aberrant neural stem or progenitor cells, including those residing in the subventricular zone, and that glioblastoma stem cells (GSCs) contribute to tumor propagation, heterogeneity, and recurrence. A key conceptual challenge is to reconcile hierarchical cancer stem cell models, in which GSCs are viewed as relatively stable tumor-propagating subpopulations, with dynamic state plasticity models, in which stem-like properties can be reversibly acquired or lost during transitions among proneural-like, mesenchymal-like, invasive, and therapy-tolerant states. Recent advances in single-cell profiling, spatial transcriptomics, lineage tracing, organoid culture, 3D bioprinting, genetically engineered models, and artificial intelligence (AI)-assisted computational modeling have substantially improved the ability to study these processes. However, no currently available model fully recapitulates human GBM heterogeneity, recurrence, treatment history, and tumor-microenvironment interactions. Therefore, model selection should be guided by clearly defined mechanistic questions rather than by reliance on any single platform. This review summarizes current advances in in vitro, ex vivo, in vivo, and computational models for studying GBM evolution and heterogeneity, and discusses how integrated model pipelines may improve preclinical drug testing, treatment-response prediction, and precision neuro-oncology.

Humans↗

High p62 and ALDH1A3 Reduce the Effectiveness of Endocrine Therapy in Luminal B Breast Cancer.

BACKGROUND/AIM: High expression of p62 and ALDH1A3 indicates a poor clinical outcome in luminal B breast cancer, and p62 is involved in the progression of ALDH1-positive luminal B breast cancer stem cells. However, the association between endocrine therapy and high p62 and ALDH1A3 expression, in luminal B breast cancer remains unclear. MATERIALS AND METHODS: Two datasets with gene expression and clinical data for patients with primary breast cancer (METABRIC, n=2,509; The Cancer Genome Atlas, n=1,084) were downloaded and statistically analyzed. To evaluate the association between the p62 and ALDH1A3 expression levels and endocrine therapy, including tamoxifen and aromatase inhibitor, in patients with luminal B breast cancer, disease-specific survival was examined using Kaplan-Meier and multivariate Cox regression analyses. RESULTS: Patients with p62 high ALDH1A3 high luminal B breast cancer treated with endocrine therapy exhibited a poor prognosis. Moreover, patients with p62 high ALDH1A3 high luminal B breast cancer treated with tamoxifen showed a trend towards a poor prognosis, but those treated with aromatase inhibitors showed a significantly poor prognosis. These results suggest that endocrine therapy, especially aromatase inhibitors, exhibits a reduced effectiveness against p62 high ALDH1A3 high luminal B tumors. CONCLUSION: p62 and ALDH1A3 could be used together as a prognostic biomarker for predicting the efficacy of endocrine therapy for luminal B breast cancer.

ALDH1A3↗