Concomitant tumor resistance: the role of tyrosine isomers in the mechanisms of metastases control

Aminoacyl-tRNA synthetase - a molecular multitasker

Aminoacyl-tRNA synthetases (AaRSs) are valuable "housekeeping" enzymes that ensure the accurate transmission of genetic information in living cells, where they aminoacylated tRNA molecules with their cognate amino acid and provide substrates for protein biosynthesis. In addition to their translational or canonical function, they contribute to nontranslational/moonlighting functions, which are mediated by the presence of other domains on the proteins. This was supported by several reports which claim that AaRS has a significant role in gene transcription, apoptosis, translation, and RNA splicing regulation. Noncanonical/ nontranslational functions of AaRSs also include their roles in regulating angiogenesis, inflammation, cancer, and other major physio-pathological processes. Multiple AaRSs are also associated with a broad range of physiological and pathological processes; a few even serve as cytokines. Therefore, the multifunctional nature of AaRSs suggests their potential as viable therapeutic targets as well. Here, our discussion will encompass a range of noncanonical functions attributed to Aminoacyl-tRNA Synthetases (AaRSs), highlighting their links with a diverse array of human diseases.

Primary tumor resection improves survival benefit of stage IVB cervical carcinoma: a new perspective

PURPOSE

Recent studies have revealed that primary tumor resection (PTR) surgery could improve prognosis in some solid tumors. Thus, we aimed to investigate whether patients with stage IVB cervical carcinoma can benefit from PTR surgery and who can benefit.

METHODS

We extracted and obtained data on patients with stage IVB cervical carcinoma from the SEER database from 2010 to 2017 and classified them into two groups: the surgery and the non-surgery group. The overall survival (OS) and cancer-specific survival (CSS) of the two groups were compared before and after propensity score matching (PSM). The independent prognostic variables were identified using univariate and multivariate Cox regression analyses. Then, the model was established to select the optimal patients to receive PTR surgery using multivariate logistic regression.

RESULTS

After PSM, the study included 476 cervical carcinoma (stage IVB) patients, of whom 238 underwent PTR surgery. Compared to the non-surgery group, the surgery group's median OS and median CSS were both longer (median OS: 27 months vs. 13 months, P < 0.001; median CSS: 52 months vs. 21 months, P < 0.001). The model showed no organ metastasis, adenocarcinoma, G1/2, and chemotherapy were more supportive of performing PTR surgery. The calibration curves and DCA showed that the model had high predictive accuracy and excellent clinical applicability. Finally, the "surgery benefit" group had the OS that was approximately four times better than "surgery non-benefit" group.

CONCLUSION

PTR surgery can potentially improve the prognosis of patients with cervical carcinoma at stage IVB. The model could probably select optimal candidates and provide a new perspective on individualized treatment.

Does Primary Tumor Resection Induce Accelerated Metastasis in Breast Cancer? A Review

INTRODUCTION

Over a century of cumulative experimental results and clinical data have suggested that surgical procedures of primary tumors promote tumor progression and metastasis in breast cancer and other cancer patients, suggesting a potential interplay linking primary tumors and distant lesions that lead to metastasis development triggered by primary tumor removal. Such evidence may generate a departure in terms of our attitude toward the surgery. However, the reliability and prognostic benefits of tumor surgery, especially for chemotherapy-resistant patients, are indisputable. Thus, it is important to explore the mechanism underlying this surgery-induced cancer progression to guide individual clinical treatment and improve tumor control.

MATERIALS AND METHODS

We conducted a comprehensive review in PubMed in October 2021 to determine the article outline. Non-English and repetitive articles were excluded. The year, topic, key findings, and opinions of each article were gathered.

RESULTS

This review not only comprehensively summarizes the potential mechanisms of primary tumors interacting with the growth of metastases but also discusses whether and how surgical resection of primary lesions can trigger tumor metastasis and development. At the same time, this article also provides our understanding of clinical findings and future directions on this topic. In addition, the combination of surgery and some potentially beneficial therapeutic interventions for postoperative tumor metastasis control was also mentioned.

CONCLUSIONS

There are viewpoints supporting an acceleration of metastasis after surgery for breast cancer and fundamental research on relevant therapies, although controversial. Further attention should be focused on the gap between current preclinical data and the complicated clinical therapeutic combination during surgery in metastatic breast cancer patients.

Toxicity of meta-Tyrosine

L-Tyrosine (Tyr) is one of the twenty proteinogenic amino acids and also acts as a precursor for secondary metabolites. Tyr is prone to modifications, especially under conditions of cellular redox imbalance. The oxidation of Tyr precursor phenylalanine leads to the formation of Tyr non-proteinogenic isomers, including meta-Tyr (m-Tyr), a marker of oxidative stress. The aim of this review is to summarize the current knowledge on m-Tyr toxicity. The direct m-Tyr mode of action is linked to its incorporation into proteins, resulting in their improper conformation. Furthermore, m-Tyr produced by some plants as an allelochemical impacts the growth and development of neighboring organisms. In plants, the direct harmful effect of m-Tyr is due to its modification of the proteins structure, whereas its indirect action is linked to the disruption of reactive oxygen and nitrogen species metabolism. In humans, the elevated concentration of m-Tyr is characteristic of various diseases and ageing. Indeed, m-Tyr is believed to play an important role in cancer physiology. Thus, since, in animal cells, m-Tyr is formed directly in response to oxidative stress, whereas, in plants, m-Tyr is also synthesized enzymatically and serves as a chemical weapon in plant-plant competition, the general concept of m-Tyr role in living organisms should be specified.

Role of nano-sensitizers in radiation therapy of metastatic tumors

Cancer metastasis remains the major cause of global cancer deaths. Radiation therapy remains one of the golden standards for cancer treatment. Nanomedicine based strategies have been designed and developed in order to improve the clinical outcomes of cancer therapy and diagnosis at molecular levels. Over the years, several researchers have shown their interest in using radiosensitizers made of high Z elements. Metal-based nanosystems also play a dual role by enhancing the synergistic effect of cell killing via various biological immune responses. This review summarizes the role of Nano-sensitizers in boosting radiation (ionizing/non-ionizing radiations) induced biological responses in treatment of metastatic cancer models.

Phase II trial of SM-88, a cancer metabolism based therapy, in non-metastatic biochemical recurrent prostate cancer

Background Androgen deprivation therapy (ADT) is a standard treatment for high-risk biochemically-recurrent, non-metastatic prostate cancer (BRPC) but is not curative and associated with toxicity. Racemetyrosine (SM-88) is an amino-acid analogue used with methoxsalen, phenytoin, and sirolimus (MPS) to enhance SM-88 activity. Method A phase 1b/2, open-label trial in BRPC and rising PSA. Patients were given daily SM-88 (230 mg BID), methoxsalen (10 mg), phenytoin (50 mg), and sirolimus (0.5 mg)). Outcome measures included changes in PSA, circulating tumor cells (CTCs) and imaging. Results 34 subjects were screened, 23 treated and 21 remained on study for ≥12 weeks. The median PSA was 6.4 ng/ml (range 1.7-80.1); doubling-time 6.2 months (range 1.4-36.6) and baseline testosterone 319.1 ng/ml (range 2.5-913.7). Median duration of therapy was 6.5 months (2.6-14.0). CTCs (median 48.5 cells/4 ml (range 15-268) at baseline) decreased a median of 65.3% in 18 of 19 patients. For patients who achieved an absolute CTC nadir count of <10 cells/4 ml (n = 10), disease control was 100% i.e. no metastases or PSA progression, while on trial (p = 0.005). PSA fell by ≥50% in 4.3% (1 subject). No patients developed metastatic disease while on treatment (metastases free survival =100%). There were no treatment-related adverse events (AEs) and quality of life was unchanged from baseline on the EORTC QLQ-C30 and QLQ-PR25. Testosterone levels rose slightly on SM-88 and were unrelated to efficacy or toxicity. Conclusions Use of SM-88 was associated with disease control while maintaining QOL. SM-88 may delay the need for ADT and the associated hormonal side effects. Larger trials are planned.Trial registration number, date of registration - NCT02796898, June 13, 2016.

Implications of immune-mediated metastatic growth on metastatic dormancy, blow-up, early detection, and treatment

Metastatic seeding of distant organs can occur in the very early stages of primary tumor development. Once seeded, these micrometastases may enter a dormant phase that can last decades. Curiously, the surgical removal of the primary tumor can stimulate the accelerated growth of distant metastases, a phenomenon known as metastatic blow-up. Recent clinical evidence has shown that the immune response can have strong tumor promoting effects. In this work, we investigate if the pro-tumor effects of the immune response can have a significant contribution to metastatic dormancy and metastatic blow-up. We develop an ordinary differential equation model of the immune-mediated theory of metastasis. We include both anti- and pro-tumor immune effects, in addition to the experimentally observed phenomenon of tumor-induced immune cell phenotypic plasticity. Using geometric singular perturbation analysis, we derive a rather simple model that captures the main processes and, at the same time, can be fully analyzed. Literature-derived parameter estimates are obtained, and model robustness is demonstrated through a time dependent sensitivity analysis. We determine conditions under which the parameterized model can successfully explain both metastatic dormancy and blow-up. The results confirm the significant active role of the immune system in the metastatic process. Numerical simulations suggest a novel measure to predict the occurrence of future metastatic blow-up in addition to new potential avenues for treatment of clinically undetectable micrometastases.

Lessons from Hippocrates: Time to Change the Cancer Paradigm

The ultimate goal of all medical activity is to restore patients to a state of complete physical, mental, and social wellbeing. In cancer, it is assumed that this can only be obtained through the complete eradication of the tumor burden. So far, this strategy has led to a substantial improvement in cancer survival rates. Despite this, more than 9 million people die from cancer every year. Therefore, we need to accept that our current cancer treatment paradigm is obsolete and must be changed. The new paradigm should reflect that cancer is a systemic disease, which affects an individual patient living in a particular social reality, rather than an invading organism or a mere cluster of mutated cells that need to be eradicated. This Hippocratic holistic view will ultimately lead to an improvement in health and wellbeing in cancer patients. They deserve nothing less.

Brain Metastases: Insights from Statistical Modeling of Size Distribution

BACKGROUND AND PURPOSE

Brain metastases are a common finding on brain MRI. However, the factors that dictate their size and distribution are incompletely understood. Our aim was to discover a statistical model that can account for the size distribution of parenchymal metastases in the brain as measured on contrast-enhanced MR imaging.

MATERIALS AND METHODS

Tumor volumes were calculated on the basis of measured tumor diameters from contrast-enhanced T1-weighted spoiled gradient-echo images in 68 patients with untreated parenchymal metastatic disease. Tumor volumes were then placed in rank-order distributions and compared with 11 different statistical curve types. The resultant R ² values to assess goodness of fit were calculated. The top 2 distributions were then compared using the likelihood ratio test, with resultant R values demonstrating the relative likelihood of these distributions accounting for the observed data.

RESULTS

Thirty-nine of 68 cases best fit a power distribution (mean R ² = 0.938 ± 0.050), 20 cases best fit an exponential distribution (mean R ² = 0.957 ± 0.050), and the remaining cases were scattered among the remaining distributions. Likelihood ratio analysis revealed that 66 of 68 cases had a positive mean R value (1.596 ± 1.316), skewing toward a power law distribution.

CONCLUSIONS

The size distributions of untreated brain metastases favor a power law distribution. This finding suggests that metastases do not exist in isolation, but rather as part of a complex system. Furthermore, these results suggest that there may be a relatively small number of underlying variables that substantially influence the behavior of these systems. The identification of these variables could have a profound effect on our understanding of these lesions and our ability to treat them.

Tyrosine aminotransferase is involved in the oxidative stress response by metabolizing meta-tyrosine in Caenorhabditis elegans

Under oxidative stress conditions, hydroxyl radicals can oxidize the phenyl ring of phenylalanine, producing the abnormal tyrosine isomer meta-tyrosine (m-tyrosine). m-Tyrosine levels are commonly used as a biomarker of oxidative stress, and its accumulation has recently been reported to adversely affect cells, suggesting a direct role for m-tyrosine in oxidative stress effects. We found that the Caenorhabditis elegans ortholog of tyrosine aminotransferase (TATN-1)-the first enzyme involved in the metabolic degradation of tyrosine-is up-regulated in response to oxidative stress and directly activated by the oxidative stress-responsive transcription factor SKN-1. Worms deficient in tyrosine aminotransferase activity displayed increased sensitivity to multiple sources of oxidative stress. Biochemical assays revealed that m-tyrosine is a substrate for TATN-1-mediated deamination, suggesting that TATN-1 also metabolizes m-tyrosine. Consistent with a toxic effect of m-tyrosine and a protective function of TATN-1, tatn-1 mutant worms exhibited delayed development, marked reduction in fertility, and shortened lifespan when exposed to m-tyrosine. A forward genetic screen identified a mutation in the previously uncharacterized gene F01D4.5-homologous with human transcription factor 20 (TCF20) and retinoic acid-induced 1 (RAI1)-that suppresses the adverse phenotypes observed in m-tyrosine-treated tatn-1 mutant worms. RNA-Seq analysis of F01D4.5 mutant worms disclosed a significant reduction in the expression of specific isoforms of genes encoding ribosomal proteins, suggesting that alterations in protein synthesis or ribosome structure could diminish the adverse effects of m-tyrosine. Our findings uncover a critical role for tyrosine aminotransferase in the oxidative stress response via m-tyrosine metabolism.

Obesity paradox in cancer: Is bigger really better?

While obesity is widely recognized as a risk factor for cancer, survival among patients with cancer is often higher for obese than for lean individuals. Several hypotheses have been proposed to explain this "obesity paradox," but no consensus has yet emerged. Here, we propose a novel hypothesis to add to this emerging debate which suggests that lean healthy persons present conditions unfavorable to malignant transformation, due to powerful natural defenses, whereby only rare but aggressive neoplasms can emerge and develop. In contrast, obese persons present more favorable conditions for malignant transformation, because of several weight-associated factors and less efficient natural defenses, leading to a larger quantity of neoplasms comprising both nonaggressive and aggressive ones to regularly emerge and progress. If our hypothesis is correct, testing would require the consideration of the raw quantity, not the relative frequency, of aggressive cancers in obese patients compared with lean ones. We also discuss the possibility that in obese persons, nonaggressive malignancies may prevent the subsequent progression of aggressive cancers through negative competitive interactions between tumors.

Investigation of tumor-tumor interactions in a double human cervical carcinoma xenograft model in nude mice

Tumor-tumor distant interactions within one organism are of major clinical relevance determining clinical outcome. To investigate this poorly understood phenomenon, a double human cervical xenograft model in nude mice was developed. A first tumor was induced subcutaneously by injection of human papillomavirus positive cervical carcinoma cells into the mouse lower right flank and 3 weeks later, animals were challenged with the same tumor cell line injected subcutaneously into the upper left flank. These tumors had no direct physical contact and we found no systemic changes induced by the primary tumor affecting the growth of a secondary tumor. However, ablation of the primary tumor by local treatment with cidofovir, a nucleotide analogue with known antiviral and antiproliferative properties, resulted not only in a local antitumor effect but also in a temporary far-reaching effect leading to retarded growth of the challenged tumor. Cidofovir far-reaching effects were linked to a reduced tumor-driven inflammation, to increased anti-tumor immune responses, and could not be enhanced by co-administration with immune stimulating adjuvants. Our findings point to the potential use of cidofovir in novel therapeutic strategies aiming to kill tumor cells as well as to influence the immune system to fight cancer.

Game-changing restraint of Ros-damaged phenylalanine, upon tumor metastasis

An abrupt increase in metastatic growth as a consequence of the removal of primary tumors suggests that the concomitant resistance (CR) phenomenon might occur in human cancer. CR occurs in murine tumors and ROS-damaged phenylalanine, meta-tyrosine (m-Tyr), was proposed as the serum anti-tumor factor primarily responsible for CR. Herein, we demonstrate for the first time that CR happens in different experimental human solid tumors (prostate, lung anaplastic, and nasopharyngeal carcinoma). Moreover, m-Tyr was detected in the serum of mice bearing prostate cancer (PCa) xenografts. Primary tumor growth was inhibited in animals injected with m-Tyr. Further, the CR phenomenon was reversed when secondary implants were injected into mice with phenylalanine (Phe), a protective amino acid highly present in primary tumors. PCa cells exposed to m-Tyr in vitro showed reduced cell viability, downregulated NFκB/STAT3/Notch axis, and induced autophagy; effects reversed by Phe. Strikingly, m-Tyr administration also impaired both, spontaneous metastasis derived from murine mammary carcinomas (4T1, C7HI, and LMM3) and PCa experimental metastases. Altogether, our findings propose m-Tyr delivery as a novel approach to boost the therapeutic efficacy of the current treatment for metastasis preventing the escape from tumor dormancy.

The immune system in cancer metastasis: friend or foe?

Metastatic disease is the leading cause of death among cancer patients and involves a complex and inefficient process. Every step of the metastatic process can be rate limiting and is influenced by non-malignant host cells interacting with the tumor cell. Over a century ago, experiments first indicated a link between the immune system and metastasis. This phenomenon, called concomitant immunity, indicates that the primary tumor induces an immune response, which may not be sufficient to destroy the primary tumor, but prevents the growth of a secondary tumor or metastases. Since that time, many different immune cells have been shown to play a role in both inhibiting and promoting metastatic disease. Here we review classic and new observations, describing the links between the immune system and metastasis that inform the development of cancer therapies.

Mathematical Modeling of Tumor-Tumor Distant Interactions Supports a Systemic Control of Tumor Growth

Interactions between different tumors within the same organism have major clinical implications, especially in the context of surgery and metastatic disease. Three main explanatory theories (competition, angiogenesis inhibition, and proliferation inhibition) have been proposed, but precise determinants of the phenomenon remain poorly understood. Here, we formalized these theories into mathematical models and performed biological experiments to test them with empirical data. In syngeneic mice bearing two simultaneously implanted tumors, growth of only one of the tumors was significantly suppressed (61% size reduction at day 15, P < 0.05). The competition model had to be rejected, whereas the angiogenesis inhibition and proliferation inhibition models were able to describe the data. Additional models including a theory based on distant cytotoxic log-kill effects were unable to fit the data. The proliferation inhibition model was identifiable and minimal (four parameters), and its descriptive power was validated against the data, including consistency in predictions of single tumor growth when no secondary tumor was present. This theory may also shed new light on single cancer growth insofar as it offers a biologically translatable picture of how local and global action may combine to control local tumor growth and, in particular, the role of tumor-tumor inhibition. This model offers a depiction of concomitant resistance that provides an improved theoretical basis for tumor growth control and may also find utility in therapeutic planning to avoid postsurgery metastatic acceleration. Cancer Res; 77(18); 5183-93. ©2017 AACR.

Investigating the Impact of a Primary Tumor on Metastasis and Dormancy Using MRI: New Insights into the Mechanism of Concomitant Tumor Resistance

Dormant cancer cells, also referred to as quiescent, slowly cycling or “nonproliferative” cells, are believed to contribute to tumor recurrence and present a therapeutic problem because they are nonresponsive to current therapies that target proliferating cells. Concomitant tumor resistance (CTR) is the ability of a primary tumor to restrict the growth of secondary metastases. In this paper, we investigate these 2 cancer concepts using cellular magnetic resonance imaging (MRI). A new model for CTR is presented where a primary mammary fat pad tumor is generated using a human breast cancer cell line (231) and breast cancer brain metastases are generated using a cell line derived from 231 to be brain metastatic (231-BR). Iron oxide particles are used to label the 231BR cells to allow for tracking of the proliferating cells, which form metastases, and the nonproliferating cells, which remain dormant in the brain. Bioluminescence and fluorescence-activated cell sorting are used to validate the MRI data. The presence of a primary 231 mammary fat pad tumor inhibited the formation of MRI-detectable 231BR brain metastases. More iron-retaining cells persisted in the brains of mice with a primary tumor. Bioluminescence and fluorescence-activated cell sorting provide evidence that signal voids detectable by MRI on day 0 represent live, iron-labeled cells in the brain. This work shows that retention of iron by nonproliferative cancer cells can be exploited to monitor the fate of this important cell population in vivo, and it points to a new mechanism for CTR, the enhancement of dormancy by a primary tumor.

Roles of the tyrosine isomers meta-tyrosine and ortho-tyrosine in oxidative stress

The damage to cellular components by reactive oxygen species, termed oxidative stress, both increases with age and likely contributes to age-related diseases including Alzheimer's disease, atherosclerosis, diabetes, and cataract formation. In the setting of oxidative stress, hydroxyl radicals can oxidize the benzyl ring of the amino acid phenylalanine, which then produces the abnormal tyrosine isomers meta-tyrosine or ortho-tyrosine. While elevations in m-tyrosine and o-tyrosine concentrations have been used as a biological marker of oxidative stress, there is emerging evidence from bacterial, plant, and mammalian studies demonstrating that these isomers, particularly m-tyrosine, directly produce adverse effects to cells and tissues. These new findings suggest that the abnormal tyrosine isomers could in fact represent mediators of the effects of oxidative stress. Consequently the accumulation of m- and o-tyrosine may disrupt cellular homeostasis and contribute to disease pathogenesis, and as result, effective defenses against oxidative stress can encompass not only the elimination of reactive oxygen species but also the metabolism and ultimately the removal of the abnormal tyrosine isomers from the cellular amino acid pool. Future research in this area is needed to clarify the biologic mechanisms by which the tyrosine isomers damage cells and disrupt the function of tissues and organs and to identify the metabolic pathways involved in removing the accumulated isomers after exposure to oxidative stress.

Comparison of clinicopathological features in metastatic upper tract urothelial carcinoma and urothelial bladder cancer

PURPOSE

To compare the characteristics of primary tumors, sites distribution of metastases and the metastasis-free interval (MFI) between metastatic upper tract urothelial carcinoma (UTUC) and urothelial bladder cancer (UBC), and evaluate the clinicopathological factors associated with MFI.

METHODS

We retrospectively reviewed 153 metastatic urothelial carcinoma patients consecutively registered at our hospital from 1997 to 2015, including 71 UTUC and 82 UBC, with a median follow-up of 18.3 months. MFI indicators were assessed by univariate and multivariate logistic regression analysis.

RESULTS

There were significant differences in median age at metastatic disease (p = 0.016), gender (p = 0.018), primary tumor size (p = 0.003), growth pattern (p < 0.001), grade (p < 0.001) and stage (p < 0.001) between metastatic UTUC and UBC. The median MFI of UTUC was dramatically shorter than that of UBC (6.1 vs. 17.4 months, p < 0.001). Univariate analysis revealed pathological stage was the only factor associated with the MFI of UTUC. Multivariate analysis showed that primary tumor grade was an independent inferior predictor for the MFI of UBC (HR 6.384, 95% CI 3.21-12.69, p < 0.001), while recurrence was an independent favorable factor for the MFI of UBC (HR 0.384, 95% CI 0.18-0.82, p = 0.014).

CONCLUSIONS

Compared to metastatic UBC, the primary tumors of metastatic UTUC were more invasive and the MFI was significantly shorter. Pathological stage was the only factor associated with the MFI in UTUC, while primary tumor grade and recurrence were independent factors for the MFI of UBC.

Role of Tyrosine Isomers in Acute and Chronic Diseases Leading to Oxidative Stress - A Review

Oxidative stress plays a major role in the pathogenesis of a variety of acute and chronic diseases. Measurement of the oxidative stress-related end products may be performed, e.g. that of structural isomers of the physiological para-tyrosine, namely meta- and ortho-tyrosine, that are oxidized derivatives of phenylalanine. Recent data suggest that in sepsis, serum level of meta-tyrosine increases, which peaks on the 2(nd) and 3(rd) days (p<0.05 vs. controls), and the kinetics follows the intensity of the systemic inflammation correlating with serum procalcitonin levels. In a similar study subset, urinary meta-tyrosine excretion correlated with both need of daily insulin dose and the insulin-glucose product in non-diabetic septic cases (p<0.01 for both). Using linear regression model, meta-tyrosine excretion, urinary meta-tyrosine/para-tyrosine, urinary ortho-tyrosine/para-tyrosine and urinary (meta- + orthotyrosine)/ para-tyrosine proved to be markers of carbohydrate homeostasis. In a chronic rodent model, we tried to compensate the abnormal tyrosine isomers using para-tyrosine, the physiological amino acid. Rats were fed a standard high cholesterol-diet, and were given para-tyrosine or vehicle orally. High-cholesterol feeding lead to a significant increase in aortic wall meta-tyrosine content and a decreased vasorelaxation of the aorta to insulin and the glucagon-like peptide-1 analogue, liraglutide, that both could be prevented by administration of para-tyrosine. Concluding, these data suggest that meta- and ortho-tyrosine are potential markers of oxidative stress in acute diseases related to oxidative stress, and may also interfere with insulin action in septic humans. Competition of meta- and ortho-tyrosine by supplementation of para-tyrosine may exert a protective role in oxidative stress-related diseases.

Conformational and vibrational analyses of meta-tyrosine: An experimental and theoretical study

M-tyrosine is one kind of positional isomer of tyrosine which is widely applied in agrichemical, medicinal chemistry, and food science. However, the structural and vibrational features of m-tyrosine have not been reported or systematically investigated. In this work, potential energy surface (PES) calculations were used for searching and determining the stable zwitterionic conformers of m-tyrosine, and the Raman spectra of m-tyrosine and deuterated m-tyrosine were measured and interpreted based on theoretical computation. For the spectral simulation, several DFT-based quantum chemistry (QC) methods were employed, and the M06-2X functional with SMD solvent model was found to be best in reproducing the Raman spectra and geometrical property. As such, this study has not only presented a detailed study of m-tyrosine's vibrational property which is lack in the literature, but also may shed some light on the optimal choice of QC methods for calculation of conformations and vibrational properties of zwitterionic amino acids.

Targeted therapies for advanced Ewing sarcoma family of tumors

The prognosis of adolescent and young adult patients battling metastatic Ewing sarcoma family of tumors (ESFT) remains less than 30% despite the development of systemic therapies. In the era of personalized medicine, novel molecular targets have been tested in preclinical or clinical settings in ESFT. In this review, we focus on early clinical and translational research that identified multiple molecular targets, including IGF-1R; mTOR; tyrosine kinase inhibitors; EWS-FLI1-related targets, and others. Overall, novel targeted therapies demonstrated modest efficacy; however pronounced and durable antineoplastic responses have been observed in small subsets of treated patients, for example with IGF-1R antibodies. Identifying outcome-predicting biomarkers and overcoming treatment resistance remain major challenges. Due to the rarity of ESFT, multi-institutional collaboration efforts of clinicians, basic and translational scientists are needed in order to understand biology of therapeutic response or resistance, which can lead to development of novel therapeutic methods and improved patient outcomes.

Incorporation of ortho- and meta-tyrosine into cellular proteins leads to erythropoietin-resistance in an erythroid cell line

BACKGROUND/AIMS

Erythropoietin-resistance is an unsolved concern in the treatment of renal anaemia. We aimed to investigate the possible role of ortho- and meta-tyrosine - the hydroxyl free radical products of L-phenylalanine - in the development of erythropoietin-resistance.

METHODS

TF-1 erythroblast cell line was used. Cell concentration was determined on day 1; 2 and 3 by two independent observers simultaneously in Bürker cell counting chambers. Protein concentration was determined with colorimetric method. Para-, ortho- and meta-tyrosine levels were measured using reverse phase-HPLC with fluorescence detection. Using Western blot method activating phosphorylation of STAT5 and ERK1/2 were investigated.

RESULTS

We found a time- and concentration-dependent decrease of erythropoietin-induced proliferative activity in case of ortho- and meta-tyrosine treated TF-1 erythroblasts, compared to the para-tyrosine cultured cells. Decreased erythropoietin-response could be regained with a competitive dose of para-tyrosine. Proteins of erythroblasts treated by ortho- or meta-tyrosine had lower para-tyrosine and higher ortho- or meta-tyrosine content. Activating phosphorylation of ERK and STAT5 due to erythropoietin was practically prevented by ortho- or meta-tyrosine treatment.

CONCLUSION

According to this study elevated ortho- and meta-tyrosine content of erythroblasts may lead to the dysfunction of intracellular signaling, resulting in erythropoietin-hyporesponsiveness.

The role of gene regulatory networks in promoting cancer progression and metastasis

ABSTRACT: 

The majority of deaths owing to cancer are ultimately caused by metastatic disease. However, most research, to date, has focused on the molecular features of cancers at their primary sites rather than on understanding disseminated malignancy in its systemic form. The dynamic nature of metastatic malignancy and its behavior as a co-ordinated systemic disease require a cancer progression paradigm that is integrative and can incorporate both the proximate causes of cancer and the broader ultimate causes in an evolutionary and developmental context. The study of robust cellular attractor states that arise directly from the architectural patterns contained within gene regulatory networks is proposed as a conceptual framework through which many of the other disparate models of cancer metastasis can be more clearly viewed and, ultimately, unified, thus providing a new conceptual framework in which to understand cancer progression and metastasis.

Stat3-targeted therapies overcome the acquired resistance to vemurafenib in melanomas

Vemurafenib (PLX4032), a selective inhibitor of Braf, has been approved by the US Food and Drug Administration for the treatment of unresectable or metastatic melanoma in patients with Braf(V600E) mutations. Many patients treated with vemurafenib initially display dramatic improvement, with decreases in both risk of death and tumor progression. Acquired resistance, however, rapidly arises in previously sensitive cells. We attempted to overcome this resistance by targeting the signal transducer and activator of transcription 3 (STAT3)-paired box homeotic gene 3 (PAX3)-signaling pathway, which is upregulated, owing to fibroblast growth factor 2 (FGF2) secretion or increased kinase activity, with the Braf(V600E) mutation. We found that activation of Stat3 or overexpression of PAX3 induced resistance to vemurafenib in melanoma cells. In addition, PAX3 or Stat3 silencing inhibited the growth of melanoma cells with acquired resistance to vemurafenib. Furthermore, treatment with the Stat3 inhibitor, WP1066, resulted in growth inhibition in both vemurafenib-sensitive and -resistant melanoma cells. Significantly, vemurafenib stimulation induced FGF2 secretion from keratinocytes and fibroblasts, which might uncover, at least in part, the mechanisms underlying targeting Stat3-PAX3 signaling to overcome the acquired resistance to vemurafenib. Our results suggest that Stat3-targeted therapy is a new therapeutic strategy to overcome the acquired resistance to vemurafenib in the treatment of melanoma.

Essential nontranslational functions of tRNA synthetases

Nontranslational functions of vertebrate aminoacyl tRNA synthetases (aaRSs), which catalyze the production of aminoacyl-tRNAs for protein synthesis, have recently been discovered. Although these new functions were thought to be 'moonlighting activities', many are as critical for cellular homeostasis as their activity in translation. New roles have been associated with their cytoplasmic forms as well as with nuclear and secreted extracellular forms that affect pathways for cardiovascular development and the immune response and mTOR, IFN-γ and p53 signaling. The associations of aaRSs with autoimmune disorders, cancers and neurological disorders further highlight nontranslational functions of these proteins. New architecture elaborations of the aaRSs accompany their functional expansion in higher organisms and have been associated with the nontranslational functions for several aaRSs. Although a general understanding of how these functions developed is limited, the expropriation of aaRSs for essential nontranslational functions may have been initiated by co-opting the amino acid-binding site for another purpose.

Concomitant tumor resistance

Concomitant tumor resistance (CR) is a phenomenon in which a tumor-bearing host is resistant to the growth of secondary tumor implants. This phenomenon has been described in human and animal systems and it can be generated by both immunogenic and non-immunogenic tumors. The relevance of CR to the mechanisms of metastases control has been highlighted by numerous observations showing that the removal of human and murine tumors may be followed by an abrupt increase in metastatic growth, suggesting that a primary tumor may exert a controlling action on its metastases which could be considered as secondary tumor implants developed spontaneously during the primary tumor growth. A more profound understanding of the different mechanisms claimed to be associated with the phenomenon of CR could contribute to develop new and more harmless means to manage malignant diseases, especially by limiting the development of metastases that arise after resection of primary tumors or after other stressors that may promote the escape of metastases from dormancy.