MYC: there is more to it than cancer.

MYC is a pleiotropic transcription factor involved in multiple cellular processes. While its mechanism of action and targets are not completely elucidated, it has a fundamental role in cellular proliferation, differentiation, metabolism, ribogenesis, and bone and vascular development. Over 4 decades of research and some 10,000 publications linking it to tumorigenesis (by searching PubMed for "MYC oncogene") have led to MYC becoming a most-wanted target for the treatment of cancer, where many of MYC's physiological functions become co-opted for tumour initiation and maintenance. In this context, an abundance of reviews describes strategies for potentially targeting MYC in the oncology field. However, its multiple roles in different aspects of cellular biology suggest that it may also play a role in many additional diseases, and other publications are indeed linking MYC to pathologies beyond cancer. Here, we review these physiological functions and the current literature linking MYC to non-oncological diseases. The intense efforts towards developing MYC inhibitors as a cancer therapy will potentially have huge implications for the treatment of other diseases. In addition, with a complementary approach, we discuss some diseases and conditions where MYC appears to play a protective role and hence its increased expression or activation could be therapeutic.

Reducing MYC's transcriptional footprint unveils a good prognostic gene signature in melanoma.

MYC's key role in oncogenesis and tumor progression has long been established for most human cancers. In melanoma, its deregulated activity by amplification of 8q24 chromosome or by upstream signaling coming from activating mutations in the RAS/RAF/MAPK pathway-the most predominantly mutated pathway in this disease-turns MYC into not only a driver but also a facilitator of melanoma progression, with documented effects leading to an aggressive clinical course and resistance to targeted therapy. Here, by making use of Omomyc, the most characterized MYC inhibitor to date that has just successfully completed a phase I clinical trial, we show for the first time that MYC inhibition in melanoma induces remarkable transcriptional modulation, resulting in severely compromised tumor growth and a clear abrogation of metastatic capacity independently of the driver mutation. By reducing MYC's transcriptional footprint in melanoma, Omomyc elicits gene expression profiles remarkably similar to those of patients with good prognosis, underlining the therapeutic potential that such an approach could eventually have in the clinic in this dismal disease.

MYC Inhibition Halts Metastatic Breast Cancer Progression by Blocking Growth, Invasion, and Seeding.

MYC's role in promoting tumorigenesis is beyond doubt, but its function in the metastatic process is still controversial. Omomyc is a MYC dominant negative that has shown potent antitumor activity in multiple cancer cell lines and mouse models, regardless of their tissue of origin or driver mutations, by impacting on several of the hallmarks of cancer. However, its therapeutic efficacy against metastasis has not been elucidated yet. Here we demonstrate for the first time that MYC inhibition by transgenic Omomyc is efficacious against all breast cancer molecular subtypes, including triple-negative breast cancer, where it displays potent antimetastatic properties both in vitro and in vivo. Importantly, pharmacologic treatment with the recombinantly produced Omomyc miniprotein, recently entering a clinical trial in solid tumors, recapitulates several key features of expression of the Omomyc transgene, confirming its clinical applicability to metastatic breast cancer, including advanced triple-negative breast cancer, a disease in urgent need of better therapeutic options. Significance: While MYC role in metastasis has been long controversial, this manuscript demonstrates that MYC inhibition by either transgenic expression or pharmacologic use of the recombinantly produced Omomyc miniprotein exerts antitumor and antimetastatic activity in breast cancer models in vitro and in vivo, suggesting its clinical applicability.

The Wnt signaling receptor Fzd9 is essential for Myc-driven tumorigenesis in pancreatic islets.

The huge cadre of genes regulated by Myc has obstructed the identification of critical effectors that are essential for Myc-driven tumorigenesis. Here, we describe how only the lack of the receptor Fzd9, previously identified as a Myc transcriptional target, impairs sustained tumor expansion and ß-cell dedifferentiation in a mouse model of Myc-driven insulinoma, allows pancreatic islets to maintain their physiological structure and affects Myc-related global gene expression. Importantly, Wnt signaling inhibition in Fzd9-competent mice largely recapitulates the suppression of proliferation caused by Fzd9 deficiency upon Myc activation. Together, our results indicate that the Wnt signaling receptor Fzd9 is essential for Myc-induced tumorigenesis in pancreatic islets.

Intrinsic cell-penetrating activity propels Omomyc from proof of concept to viable anti-MYC therapy.

Inhibiting MYC has long been considered unfeasible, although its key role in human cancers makes it a desirable target for therapeutic intervention. One reason for its perceived undruggability was the fear of catastrophic side effects in normal tissues. However, we previously designed a dominant-negative form of MYC called Omomyc and used its conditional transgenic expression to inhibit MYC function both in vitro and in vivo. MYC inhibition by Omomyc exerted a potent therapeutic impact in various mouse models of cancer, causing only mild, well-tolerated, and reversible side effects. Nevertheless, Omomyc has been so far considered only a proof of principle. In contrast with that preconceived notion, here, we show that the purified Omomyc mini-protein itself spontaneously penetrates into cancer cells and effectively interferes with MYC transcriptional activity therein. Efficacy of the Omomyc mini-protein in various experimental models of non-small cell lung cancer harboring different oncogenic mutation profiles establishes its therapeutic potential after both direct tissue delivery and systemic administration, providing evidence that the Omomyc mini-protein is an effective MYC inhibitor worthy of clinical development.

Effect of cellular senescence on the growth of HER2-positive breast cancers.

BACKGROUND: Oncogene-induced senescence (OIS) is a tumor suppressor mechanism. However, senescent cells remain viable and display a distinct secretome (also known as senescence-associated secretory phenotype [SASP] or senescence messaging secretome, [SMS]) that, paradoxically, includes protumorigenic factors. OIS can be triggered by ectopic overexpression of HER2, a receptor tyrosine kinase and the driving oncogene in a subtype of human breast cancer. However, cellular senescence has not been characterized in HER2-positive tumors. METHODS: Using an approach based on their inability to proliferate, we isolated naturally occurring senescent cells from a variety of tumor models including HER2-positive cells, transgenic mice (n = 3), and patient-derived xenografts (PDXs) (n = 6 mice per group from one PDX derived from one patient). Using different biochemical and cell biological techniques, we characterized the secretome of these senescent cells. All statistical tests were two-sided. RESULTS: We found that senescent cells arise constantly in different models of advanced breast cancers overexpressing HER2 and constitute approximately 5% of tumor cells. In these models, IL-6 and other cytokines were expressed mainly, if not exclusively, by the naturally occurring senescent cells (95.1% and 45.0% of HCC1954 cells and cells from a HER2-positive PDX expressing a senescent marker expressed IL-6, respectively). Furthermore, inhibition of IL-6 impaired the growth of the HER2-positive PDX (mean tumor volume at day 101, control vs anti-huIL-6 treated, 332.2mm(3) [95% confidence interval {CI} = 216.6 to 449.8] vs 114.4mm(3) [95% CI = 12.79 to 216.0], P = .005). CONCLUSIONS: Senescent cells can contribute to the growth of tumors by providing cytokines not expressed by proliferating cells, but required by these to thrive.

Constitutive HER2 signaling promotes breast cancer metastasis through cellular senescence.

Senescence, a terminal cell proliferation arrest, can be triggered by oncogenes. Oncogene-induced senescence is classically considered a tumor defense barrier. However, several findings show that, under certain circumstances, senescent cells may favor tumor progression because of their secretory phenotype. Here, we show that the expression in different breast epithelial cell lines of p95HER2, a constitutively active fragment of the tyrosine kinase receptor HER2, results in either increased proliferation or senescence. In senescent cells, p95HER2 elicits a secretome enriched in proteases, cytokines, and growth factors. This secretory phenotype is not a mere consequence of the senescence status and requires continuous HER2 signaling to be maintained. Underscoring the functional relevance of the p95HER2-induced senescence secretome, we show that p95HER2-induced senescent cells promote metastasis in vivo in a non-cell-autonomous manner.

Inmunomodulación y antiangiogénesis en la terapéutica oncológica: De la investigación básica a la clínica / Immunomodulation and antiangiogenesis in cancer therapy: From basic to clinical research

La investigación básica y pre-clínica en oncología celular y molecular son pilares fundamentales en los que se apoyan la mayoría de los adelantos en la terapéutica del cáncer. Los hallazgos obtenidos y su aplicación en la práctica clínica constituyen la causa del avance sostenido en el tratamiento de la enfermedad neoplásica. El objetivo de este trabajo es resumir y discutir los resultados pre-clínicos en inmunomodulación y anti-angiogénesis para el tratamiento de diversos tipos de tumores, obtenidos en nuestro Instituto durante los últimos 15 años, y la posterior traslación y aplicación del conocimiento experimental en un Ensayo Clínico Fase I/II. Se describen los resultados que contribuyeron a descifrar los mecanismos de acción de la inmunomodulación antimetastásica con ciclofosfamida, la quimioterapia metronómica con diferentes drogas únicas o combinaciones, y finalmente el diseño y resultados preliminares de un ensayo clínico de quimioterapia metronómica para pacientes con cáncer de mama avanzado.

Basic and pre-clinic research in cellular and molecular oncology are the main supports accounting for the advancement in cancer therapeutics. The findings achieved, and their implementation in clinical practice are responsible for the permanent improvement in the treatment of the neoplastic disease. Our present objective is to summarize and discuss the pre-clinical findings in immunomodulation and anti-angiogenesis for the treatment of several types of tumors obtained in our Institute during the last 15 years, and the subsequent translation and application of the acquired experimental knowledge in a Phase I/II Clinical Trial. We present the results and mechanisms of action of antimetastatic immunomodulation with cyclophosphamide, the metronomic chemotherapy with different single drugs and their combinations, and finally the design and preliminary results of a clinical trial with metronomic chemotherapy for patients with advanced breast cancer.

[Immunomodulation and antiangiogenesis in cancer therapy. From basic to clinical research]. / Inmunomodulación y antiangiogénesis en la terapéutica oncológica. De la investigación básica a la clínica.

Basic and pre-clinic research in cellular and molecular oncology are the main supports accounting for the advancement in cancer therapeutics. The findings achieved, and their implementation in clinical practice are responsible for the permanent improvement in the treatment of the neoplastic disease. Our present objective is to summarize and discuss the pre-clinical findings in immunomodulation and anti-angiogenesis for the treatment of several types of tumors obtained in our Institute during the last 15 years, and the subsequent translation and application of the acquired experimental knowledge in a Phase I/II Clinical Trial. We present the results and mechanisms of action of antimetastatic immunomodulation with cyclophosphamide, the metronomic chemotherapy with different single drugs and their combinations, and finally the design and preliminary results of a clinical trial with metronomic chemotherapy for patients with advanced breast cancer.

The aggressiveness of murine lymphomas selected in vivo by growth rate correlates with galectin-1 expression and response to cyclophosphamide.

Although lymphomas account for almost half of blood-derived cancers that are diagnosed each year, the causes of new cases are poorly understood, as reflected by the relatively few risk factors established. Galectin-1, an immunoregulatory ß-galactoside-binding protein, has been widely associated with tumor-immune escape. The aim of the present work was to study the relationship between tumor growth rate, aggressiveness, and response to cyclophosphamide (Cy) therapy with regard to Gal-1 expression in murine T-cell lymphoma models. By means of a disruptive selection process for tumor growth rate, we generated two lymphoma variants from a parental T-cell lymphoma, which have unique characteristics in terms of tumor growth rate, spontaneous regression, metastatic capacity, Gal-1 expression and sensitivity to Cy therapy. Here, we show that Gal-1 expression strongly correlates with tumor growth rate, metastatic capacity and response to single-dose Cy therapy in T-cell lymphoma models; this association might have important consequences for evaluating prognosis and treatments of this type of tumors.

The immune response and the therapeutic effect of metronomic chemotherapy with cyclophosphamide.

Metronomic chemotherapy (MCT) is a novel therapeutic strategy for cancer treatment endowed with an antiangiogenic effect. It refers to regular administration of low doses of cytotoxic drugs, with minimal or no drug-free breaks. Previously, we demonstrated the immunomodulating activity of a single low-dose of cyclophosphamide (Cy) and the antitumor effect of MCT with Cy on established rat lymphomas and sarcomas. Here, we examined whether the immune response is responsible for the antitumor effect of MCT with Cy on L-TACB lymphoma. Inbred e rats and nude mice were subcutaneously challenged with L-TACB. After 7 days, they were distributed into two experimental groups: 1) treated animals, which were injected IP with Cy (10 mg/kg body weight) three times per week, and 2) control animals, which received IP saline injections. Exponential growth and decay and tumor doubling time were calculated. Also, serum IL-10 levels were measured. One hundred percent of treated rats showed tumor regression versus 0% of control rats. The increase of tumor-induced IL-10 levels was reverted by the treatment with Cy. On the other hand, there were no tumor regressions, in treated or control nude mice. However, the tumor doubling times of treated nude mice were significantly higher than those of control mice, implying that other antitumor mechanism(s), independent of the adaptive immune response, might be taking place. Our present results indicate that modulation of the immune response would be involved in the antitumor effect of MCT with Cy, because the absence of the specific immune response impairs, at least in part, its therapeutic effect in a lymphoma tumor model.

Dynamic cross-talk between tumor and immune cells in orchestrating the immunosuppressive network at the tumor microenvironment.

Accumulating evidence indicates that a dynamic cross-talk between tumors and the immune system can regulate tumor growth and metastasis. Increased understanding of the biochemical nature of tumor antigens and the molecular mechanisms responsible for innate and adaptive immune cell activation has revolutionized the fields of tumor immunology and immunotherapy. Both the protective effects of the immune system against tumor cells (immunosurveillance) and the evasion of tumor cells from immune attack (tumor-immune escape) have led to the concept of cancer immunoediting, a proposal which infers that a bidirectional interaction between tumor and inflammatory/regulatory cells is ultimately responsible for orchestrating the immunosuppressive network at the tumor site. In this context, a major challenge is the potentiation or redirection of tumor antigen-specific immune responses. The success in reaching this goal is highly dependent on an improved understanding of the interactions and mechanisms operating during the different phases of the cancer immunoediting process. In this review, we discuss the multiple defense and counterattack strategies that tumors have devised in order to evade immune attack and to thwart the effectiveness of several immunotherapeutic approaches.

Low-dose cyclophosphamide modulates galectin-1 expression and function in an experimental rat lymphoma model.

In recent years, one of the most important insights into tumor immunity was provided by the identification of negative regulatory pathways and immune escape strategies that greatly influence the magnitude of antitumor responses. Galectin-1 (Gal-1), a member of a family of highly conserved beta-galactoside-binding proteins, has been recently shown to contribute to tumor cell evasion of immune responses by modulating survival and differentiation of effector T cells. However, there is still scarce information about the regulation of Gal-1 expression and function in vivo. Here we show that administration of a single low-dose cyclophosphamide (Cy), which is capable of restraining metastasis in the rat lymphoma model L-TACB, can also influence Gal-1 expression in primary tumor, metastasis, and spleen cells and modulate the effects of this protein on T cell survival. A time-course study revealed a positive correlation between Gal-1 expression and tumor volume in primary tumor cells. Conversely, Gal-1 expression was significantly reduced in spleen cells and lymph node metastasis throughout the period studied. Interestingly, cyclophosphamide treatment was capable of restoring the basal levels of Gal-1 expression in primary tumors and spleens. In addition, this antimetastatic agent rendered spleen T cells from tumor-bearing animals resistant to Gal-1-induced cell death. Our results suggest that, in addition to other well-known functions of cyclophosphamide, this immunomodulatory agent may also modulate Gal-1 expression and function during tumor growth and metastasis with critical implications for tumor-immune escape and immunotherapy.