The Potential Value of Ki-67 in Prognostic Classification in Early Low-Risk Endometrial Cancer.

PURPOSE: This study aims to determine the optimal cut-off value of Ki-67 to better predict the recurrence of early low-risk endometrial cancer (EC). METHODS: Seven hundred and forty-eight patients diagnosed with low-risk EC from West China Second Hospital of Sichuan University and the First Affiliated Hospital of Chongqing Medical University were retrospectively analyzed. The receiver operating characteristic curve (ROC) and Youden index were used to calculate the optimal cut-off value of Ki-67 expression. The clinicopathological indexes between two groups divided by cut-off value of Ki-67 were compared. The univariate and multivariate regression analyses were performed to investigate risk factors connected to the recurrence of early low-risk EC. The survival analysis was shown in Kaplan-Meier curve. RESULT: Thirty-three patients were detected with tumor recurrence after primary surgery (4.4%); 33% was the optimal cut-off value of the Ki-67 index. A high Ki-67 was significantly associated with age (P = .002), myometrial invasion (P < .001), and the expression of P53 (P = .007). The multivariate regression analysis verified that Ki67 ≥ 33% was an independent prognostic factor for predicting recurrence. The recurrence-free survival (RFS) and the overall survival (OS) in high Ki-67 group was significantly lower than that in low Ki-67 group (P < .001 and P = .029, respectively). The prognostic values of ER, PR, and P53 in combination with Ki-67 were superior to each single predictor. CONCLUSIONS: The optimal cut-off value of Ki-67 for predicting recurrence is 33%, which quantitatively defines the specific value of Ki-67 that causes high-risk recurrence in early low-risk EC.

Receptor tyrosine kinases activate heterotrimeric G proteins via phosphorylation within the interdomain cleft of Gαi.

The molecular mechanisms by which receptor tyrosine kinases (RTKs) and heterotrimeric G proteins, two major signaling hubs in eukaryotes, independently relay signals across the plasma membrane have been extensively characterized. How these hubs cross-talk has been a long-standing question, but answers remain elusive. Using linear ion-trap mass spectrometry in combination with biochemical, cellular, and computational approaches, we unravel a mechanism of activation of heterotrimeric G proteins by RTKs and chart the key steps that mediate such activation. Upon growth factor stimulation, the guanine-nucleotide exchange modulator dissociates Gαi•ßγ trimers, scaffolds monomeric Gαi with RTKs, and facilitates the phosphorylation on two tyrosines located within the interdomain cleft of Gαi. Phosphorylation triggers the activation of Gαi and inhibits second messengers (cAMP). Tumor-associated mutants reveal how constitutive activation of this pathway impacts cell's decision to "go" vs. "grow." These insights define a tyrosine-based G protein signaling paradigm and reveal its importance in eukaryotes.

Singular Spectrum Analysis for Modal Estimation from Stationary Response Only.

Conventional experimental modal analysis uses excitation and response information to estimate the frequency response function. However, many engineering structures face excitation signals that are difficult to measure, so output-only modal estimation is an important issue. In this paper, singular spectrum analysis is employed to construct a Hankel matrix of appropriate dimensions based on the measured response data, and the observability of the system state space model is used to treat the Hankel matrix as three components containing system characteristics, excitation and noise. Singular value decomposition is used to factorize the data matrix and use the characteristics of the left and right singular matrices to reduce the dimension of the data matrix to improve calculation efficiency. Furthermore, the singular spectrum is employed to estimate the minimum order to reconstruct the Hankel matrix; then, the excitation and noise components can be removed, and the system observability matrix can be obtained. By appropriately a factorizing system observability matrix, we obtain the system matrix to estimate the modal parameters. In addition, the fictitious modes produced by increasing the order of the matrix can be eliminated through the stabilization diagram.

Independent Prognostic Value of Hypoxia-inducible Factor 1-alpha Expression in Small Cell Lung Cancer.

Hypoxia is an important factor in tumor angiogenesis, metastasis, and resistance to chemotherapy or radiotherapy, and may be an indicator of poor prognosis. The transcription factor hypoxia-inducible factor 1 (HIF-1) is the key regulator of the hypoxic state. This study was designed to evaluate the prognostic value of HIF-1α expression in small cell lung cancer (SCLC). Forty-three paraffin-embedded biopsy materials were examined using immunohistochemistry. Our results indicated that the expression of HIF-1α was high in males, and patients with poor Eastern Cooperative Oncology Group (ECOG) performance status and metastases. To elucidate the prognostic value of HIF-1α expression, Kaplan-Meier analysis was carried out and the results showed that patients with high HIF-1α expression had a poorer prognosis than patients with low expression of HIF-1α. After adjusting clinical parameters by the Cox proportional hazards model, our results demonstrated that high HIF-1α expression is an independent prognostic factor for SCLC with a 39.2-fold risk of death (p<0.003). In conclusion, we have provided evidence that HIF-1α expression has significant value in predicting survival of patients with SCLC and is an independent prognostic factor beyond ECOG performance and metastasis status.

Evaluating the Prognostic Value of ERCC1 and Thymidylate Synthase Expression and the Epidermal Growth Factor Receptor Mutation Status in Adenocarcinoma Non-Small-Cell Lung Cancer.

The present study evaluated the prognostic value of the epidermal growth factor receptor (EGFR) mutation status, and excision repair cross-complementation group 1 (ERCC1) and thymidylate synthase (TS) expression following intercalated tyrosine kinase inhibitor (TKI) therapy and platinum- and pemetrexed-based chemotherapies (subsequent second-line treatment) for patients with adenocarcinoma non-small-cell lung cancer (AC-NSCLC). In total, 131 patients with AC-NSCLC were enrolled. The EGFR mutation status and ERCC1 and TS expression were evaluated through direct DNA sequencing and immunohistochemical analyses, respectively. The EGFR mutation status and ERCC1 and TS expression were the significant predictors of clinical outcomes. The EGFR mutation status was the main outcome predictor for overall survival (OS) benefits in the overall population. Further exploratory ERCC1 and TS expression analyses were conducted to provide additional insights. Low TS expression was predictive of improved OS of patients with negative EGFR-mutated advanced AC-NSCLC, whereas high ERCC1 expression resulted in poor OS in patients with positive EGFR-mutated advanced AC-NSCLC. TS and ERCC1 expression levels were effective prognostic factors for negative and positive EGFR-mutated AC-NSCLC, respectively. In conclusion, the present results indicate that the EGFR mutation status and TS and ERCC1 expression can be used as the predictors of OS after subsequent second-line treatments for AC-NSCLC.

Chronic Influences of Obstructive Sleep Apnea on Cerebral Venous Flow.

OBJECTIVES: Evidence reveals a pathophysiologic link between sleep apnea syndrome and cerebrovascular diseases. It is known that obstructive sleep apnea (OSA) may cause serial hemodynamic changes and structural abnormalities in the cerebral and cardiac arterial systems, but its effect on the cerebral venous system has remained unclear. The purpose of this study was to compare internal jugular vein hemodynamics between patients with OSA and healthy individuals. METHODS: Patients with OSA and age-, body mass index-, and sex-matched healthy control participants were recruited for a jugular venous duplex study and neurologic examination. The luminal area of the internal jugular vein, jugular venous flow volume, time-averaged mean velocity, and presence of jugular venous reflux were recorded. These flow characteristics were obtained at different respiratory statuses, and we analyzed the differences between patients and controls. RESULTS: In the OSA group, there was an increasing flow volume in total internal jugular veins at rest. The frequency of venous reflux in patients compared with controls was significantly decreased (26.7% versus 53.3%, respectively; P < .05). The internal jugular vein drainage dominance was greater on the left side in the OSA group (right versus left: 48.8% versus 51.2%), whereas it was greater on the right side in the control group (right versus left: 61.7% versus 38.3%). CONCLUSIONS: Our data showed peculiar internal jugular vein hemodynamics at baseline and different respiratory statuses in patients with OSA. These characteristics imply that cerebral venous drainage conditions might be involved in the pathophysiologic mechanisms of OSA syndrome.

The CYP1B1 Leu432Val polymorphism and risk of urinary system cancers.

The cytochrome P450 1B1 (CYP1B1) gene plays a key role in the metabolism of various carcinogens. The CYP1B1 Leu432Val polymorphism leads to leucine to valine substitution at codon 432. A lot of studies have shown that the CYP1B1 Leu432Val polymorphism was associated with urinary system cancers, especially prostate cancer. However, the results were still inconclusive. In this meta-analysis, by searching online databases and references of related reviews, we identified 17 eligible studies to assess the relationship between CYP1B1 Leu432Val polymorphism and urinary system cancers, including 7,783 cancer cases and 7,238 controls. By pooling all eligible studies, we found that the CYP1B1 Leu432Val polymorphism was not associated with overall urinary system cancers. However, in subgroup analyses, we found that the variant 432Val allele significantly increased the risk of prostate cancer (Val vs. Leu, odds ratio (OR) = 1.064, 95% confidence interval (CI) 0.981-1.154; Pheterogeneity = 0.002), while no association was found for bladder cancer (Val vs. Leu, OR = 0.942, 95% CI 0.853-1.041; Pheterogeneity = 0.504). No evidence of publication bias was found (Begg's test, P = 0.053; Egger's test, P = 0.073). In conclusion, based on 17 eligible studies, we found that the CYP1B1 Leu432Val polymorphism was associated with an increased risk of prostate cancer, while no association of bladder cancer was observed.

The role of circRNAs in regulation of drug resistance in ovarian cancer.

Ovarian cancer is one of the female reproductive system tumors. Chemotherapy is used for advanced ovarian cancer patients; however, drug resistance is a pivotal cause of chemotherapeutic failure. Hence, it is critical to explore the molecular mechanisms of drug resistance of ovarian cancer cells and to ameliorate chemoresistance. Noncoding RNAs (ncRNAs) have been identified to critically participate in drug sensitivity in a variety of human cancers, including ovarian cancer. Among ncRNAs, circRNAs sponge miRNAs and prevent miRNAs from regulation of their target mRNAs. CircRNAs can interact with DNA or proteins to modulate gene expression. In this review, we briefly describe the biological functions of circRNAs in the development and progression of ovarian cancer. Moreover, we discuss the underneath regulatory molecular mechanisms of circRNAs on governing drug resistance in ovarian cancer. Furthermore, we mention the novel strategies to overcome drug resistance via targeting circRNAs in ovarian cancer. Due to that circRNAs play a key role in modulation of drug resistance in ovarian cancer, targeting circRNAs could be a novel approach for attenuation of chemoresistance in ovarian cancer.

A Nomogram Model Based on Neuroendocrine Markers for Predicting the Prognosis of Neuroendocrine Carcinoma of Cervix.

BACKGROUND: Combining traditional clinical parameters with neuroendocrine markers to construct a nomogram model to predict the postoperative recurrence of neuroendocrine carcinoma of cervix (NECC). METHODS: A total of 257 patients were included in this study. Univariate and multivariate Cox regression analyses were used to establish a nomogram model in the training cohorts, which was further validated in the validation cohorts. The calibration curve was used to conduct the internal and external verification of the model. RESULTS: Overall, 41 relapse cases were observed in the training (23 cases) and validation (18 cases) cohorts. The univariate analysis preliminarily showed that FIGO stage, stromal invasion, nerve invasion, lymph vascular space invasion, lymph node involvement, cervical-uterine junction invasion and CgA were correlated with NECC recurrence. The multivariate analysis further confirmed that FIGO stage (p = 0.023), stromal invasion (p = 0.002), lymph vascular space invasion (p = 0.039) and lymph node involvement (p = 0.00) were independent risk factors for NECC recurrence, which were ultimately included in the nomogram model. In addition, superior consistency indices were demonstrated in the training (0.863, 95% CI 0.784-0.942) and validation (0.884, 95% CI 0.758-1.010) cohorts. CONCLUSIONS: The established nomogram model combining traditional clinical parameters with neuroendocrine markers can reliably and accurately predict the recurrence risks in NECC patients.

Risk factors of emergency cesarean section in pregnant women with severe placenta accreta spectrum: a retrospective cohort study.

Introduction: Placenta accreta spectrum (PAS) may cause enormous and potentially life-threatening hemorrhage in the intrapartum and postpartum periods in emergency cesarean section. How to reduce the occurrence of emergency cesarean section in patients with severe PAS is the key to reducing the adverse outcomes of them. This study aimed to investigate the impact of emergency cesarean section on the perioperative outcomes of pregnant women with PAS and neonates, and also aimed to explore the risk factors of emergency cesarean section in pregnant women with PAS. Materials and methods: A retrospective investigation was conducted among 163 pregnant women with severe PAS. Of these, 72 were subjected to emergency cesarean sections. Data on the perioperative characteristics of the mothers and neonates were collected. Multivariable linear regression analysis was used to detect associations between maternal and perioperative characteristics and volume of intraoperative bleeding. Binary logical regression was used to analyze the association between maternal preoperative characteristics and emergency cesarean section. Linear regression analysis is used to analyze the relationship between gestational age and emergency cesarean section. Results: The risks of emergency cesarean section increase 98, 112, 124, and 62% when the pregnant women with PAS accompanied by GHD, ICP, more prior cesarean deliveries and more severe PAS type, respectively. Noteworthy, the risk of emergency cesarean section decreases 5% when pre-pregnancy BMI increases 1 kg/m2 (OR: 0.95; CI: 0.82, 0.98; p = 0.038). Moreover, there is no significant linear correlation between emergency cesarean section and gestational age. Conclusion: GHD, ICP, multiple prior cesarean deliveries and severe PAS type may all increase the risk of emergency cesarean section for pregnant women with PAS, while high pre-pregnancy BMI may be a protective factor due to less activity level. For pregnant women with severe PAS accompanied by these high risk factors, more adequate maternal and fetal monitoring should be carried out in the third trimester to reduce the risk of emergency cesarean section.

Identification of furo[3', 2':3,4]naphtho[1,2-d]imidazole derivatives as orally active and selective inhibitors of microsomal prostaglandin E(2) synthase-1 (mPGES-1).

This study describes the synthesis and anti-inflammatory effects of furo[3', 2':3,4]naphtho[1,2-d] imidazole derivatives. Among these furo[3', 2':3,4]naphtho[1,2-d]imidazole derivatives, 2-(4-methoxyphenyl)furo [3', 2':3,4]naphtho[1,2-d]imidazole (12) exhibited a strong inhibitory activity against LPS-induced PGE(2) production, with an IC(50) value of 47 nM. Compound 12 is then further examined for its inhibitory effects in the protein expression of COX-2 and microsomal prostaglandin E(2) synthase-1 (mPGES-1) in Raw 264.7 cells. Our results indicate that compound 12 was capable against inhibiting LPS-induced mPGES-1 protein expression at a concentration of 1.0 µM and no inhibitory effect in COX-2 expression. The sepsis-induced PGE(2) production in rat serum decreased ~250% by the pretreatment of 12 at 10 mg/kg. These results are especially important since compound 12 exhibited good oral bioavailability (72%) and was not cytotoxic at a concentration of 10.0 µM. Therefore, compound 12 is a highly selective mPGES-1 inhibitor that can serve as a lead for the development of novel oral anti-inflammatory drug candidates.

Corrigendum: Effects of virtual reality-based intervention on cognition, motor function, mood, and activities of daily living in patients with chronic stroke: A systematic review and meta-analysis of randomized controlled trials.

[This corrects the article DOI: 10.3389/fnagi.2021.766525.].

Effects of Virtual Reality-Based Intervention on Cognition, Motor Function, Mood, and Activities of Daily Living in Patients With Chronic Stroke: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.

Background: The efficacy of virtual reality (VR)-based intervention for improving cognition in patients with the chronic stage of stroke is controversial. The aims of this meta-analysis were to evaluate the effect of VR-based training combined with traditional rehabilitation on cognition, motor function, mood, and activities of daily living (ADL) after chronic stroke. Methods: The search was performed in the Cochrane Library (CENTRAL), EBSCO, EMBASE, Medline (OVID), Web of Science databases, PubMed, CINAHL Ovid, and Scopus from inception to May 31, 2021. All included studies were randomized controlled trials (RCTs) examining VR-based intervention combined with traditional rehabilitation for chronic stroke. The main outcomes of this study were cognition, including overall cognition (combined with all cognitive measurement results), global cognition (measured by the Montreal Cognitive Assessment, MoCA, and/or Mini-Mental State Examination, MMSE), and attention/execution. The additional outcomes were motor function, mood, and ADL. Subgroup analyses were conducted to verify the potential factors for heterogeneity. Results: Six RCTs including 209 participants were included for systematic review, and five studies of 177 participants were included in meta-analyses. Main outcome analyses showed large and significant effect size (ES) of VR-based training on overall cognition (g = 0.642; 95% CI = 0.134-1.149; and P = 0.013) and attention/execution (g = 0.695; 95% CI = 0.052-1.339; and P = 0.034). Non-significant result was found for VR-based intervention on global cognition (g = 0.553; 95% CI = -0.273-1.379; and P = 0.189). Additional outcome analyses showed no superiority of VR-based intervention over traditional rehabilitation on motor function and ADL. The ES of VR-based intervention on mood (g = 1.421; 95% CI = 0.448-2.393; and P = 0.004) was large and significant. In the subgroup analysis, large effects for higher daily intensity, higher weekly frequency, or greater dose of VR intervention were found. Conclusion: Our findings indicate that VR-based intervention combined with traditional rehabilitation showed better outcomes for overall cognition, attention/execution, and depressive mood in individuals with chronic stroke. However, VR-based training combined with traditional rehabilitation showed a non-significant effect for global cognition, motor function, and ADL in individuals with chronic stroke.

Furo[3',2':3,4]naphtho[1,2-d]imidazole derivatives as potential inhibitors of inflammatory factors in sepsis.

Synthesis and anti-inflammatory effects of certain furo[3',2':3,4]naphtho[1,2-d]imidazole derivatives 12-18 were studied. These compounds were synthesized from naphtho[1,2-b]furan-4,5-dione (10) which in turn was prepared from the known 2-hydroxy-1,4-naphthoquinone (7) in a one pot reaction. Furo[3',2':3,4]naphtho[1,2-d]imidazole (12) was inactive (IC(50) value of >30 microM) while its 5-phenyl derivative 13, with an IC(50) value of 16.3 and 11.4 microM against lysozyme and beta-glucuronidase release, respectively, was comparable to the positive trifluoperazine. The same potency was observed for 5-furan derivative 16 with an IC(50) value of 19.5 and 11.3 microM against lysozyme and beta-glucuronidase release, respectively. An electron-withdrawing NO(2) substituted on 5-phenyl or 5-furanyl group led to the devoid of activity as in the cases of 14 and 17. Among them, compound 15 exhibited significant inhibitory effects, with an IC(50) value of 7.4 and 5.0 microM against lysozyme and beta-glucuronidase release, respectively. For the LPS-induced NO production, the phenyl derivatives 12-15 were inactive while the nitrofuran counterparts 17 and 18 suppress LPS-induced NO production significantly, with an IC(50) value of 1.5 and 1.3 microM, respectively, which are more active than that of the positive 1400 W. Compounds 16-18 were capable of inhibiting LPS-induced iNOS protein expression at a dose-dependent manner in which compound 18, with an IC(50) of 0.52 microM in the inhibition of iNOS expression, is approximately fivefold more potent than that of the positive 1400 W. In the CLP rat animal model, compound 18 was found to be more active than the positive hydrocortisone in the inhibition of the iNOS mRNA expression in rat lung tissue. The sepsis-induced PGE2 production in rat serum decreased 150% by the pretreatment of 18 in a dose of 10 mg/kg.

Telomerase immortalization of human neural progenitor cells.

It is necessary to expand human neural progenitor cells in vitro to obtain large numbers for research purposes and cell transplantation. A potential obstacle to in vitro expansion, however, is that neural progenitor cells have a limited replication life-span and gradually lose their differentiation potential. We report here that ectopic expression of the catalytic subunit of human telomerase (hTERT) gene in neural progenitor cells could induce telomerase activity, stabilize telomeres and extend their replicative life-spans. The telomerase-immortalized cells (hNPC-TERT) maintained the normal diploid karyotype, expressed the markers of human neural progenitor cells and meanwhile held the differentiation potential in vitro for up to 120 population doublings. This study provides a new approach for obtaining unlimited quantities of normal phenotypic and homogeneous human neural progenitor cells in vitro.

Fetal human neural progenitors can be the target for tumor transformation.

The hypothesis that stem cells may seed cancer has emerged from the cancer stem cells concept. However, the experimental systems necessary to provide more direct evidence to support the hypothesis have been lacking. We have used fetal neural progenitor cells (hNPC) transduced with the telomerase hTERT gene to investigate the neoplastic potential of hNPCs. The hTERT-transduced line, hNPCs-G3 lost normal diploid karyotype, showed loss of contact inhibition, anchorage independence, and formed neuroblastoma-like tumours in all of 10 mice. These data suggest that hNPCs have the potential for neoplastic transformation. These data have implications for providing a novel tool to test the feasibility of new anticancer treatment strategies and raise the possibility of a risk for the use of hNPCs in cell transplantation.

[The induction of neuronal differentiation in the glial fibrillary acid protein positive human neural progenitor cell line].

OBJECTIVE: To investigate the ability of human GFAP positive neural progenitor cell line from the subventricular zone (SVZ) to differentiate into neurons. METHODS: Real-time RT-PCR, Western blot analysis and immunocytochemistry were used to examine the expression level of the neural stem cell marker and neuronal-specific marker before and after all-trans-retinoic acid (AT-RA) induction in the GFAP positive neural progenitor cell line. Immunocytochemistry was used to examine the expression of the neuronal-specific marker after transplantation the GFAP positive neural progenitor cell line into the animal model. RESULTS: After induction, in the GFAP positive neural progenitor cell line the expression levels of the neuronal-specific marker increased, while the neural stem cell marker decreased both in mRNA and protein levels. After transplantation into animal model, the GFAP positive neural progenitor cell line could differentiate into neurons. CONCLUSION: The GFAP positive neural progenitor cell line could be induced to differentiate into neurons both in vitro and in vivo.

[Induced expression of dopamine D2 receptor in human neuro-progenitor cell line HNG1210-E].

OBJECTIVE: To investigate whether the dopamine receptor D2 can express or can be induced to express in HNG1210-E, a monoclonal, telomerase-immortalized, human neural progenitor cell line. METHODS: By means of RT-PCR, immuno-fluorescent staining, and fluo3 Ca2+ imaging to the expression of D2 mRNA and protein as well as the reaction to dopamine were demonstrated. RESULTS: HNG1210-E cells could be induced to express D2 mRNA and its proteins. The induced cells also reacted to dopamine (5 mmol.L-1), which caused rapid rising of cytoplasm Ca2+. CONCLUSION: HNG1210-E cells can be induced to express D2 mRNA and functional proteins.

Structural basis for activation of trimeric Gi proteins by multiple growth factor receptors via GIV/Girdin.

A long-standing issue in the field of signal transduction is to understand the cross-talk between receptor tyrosine kinases (RTKs) and heterotrimeric G proteins, two major and distinct signaling hubs that control eukaryotic cell behavior. Although stimulation of many RTKs leads to activation of trimeric G proteins, the molecular mechanisms behind this phenomenon remain elusive. We discovered a unifying mechanism that allows GIV/Girdin, a bona fide metastasis-related protein and a guanine-nucleotide exchange factor (GEF) for Gαi, to serve as a direct platform for multiple RTKs to activate Gαi proteins. Using a combination of homology modeling, protein-protein interaction, and kinase assays, we demonstrate that a stretch of ∼110 amino acids within GIV C-terminus displays structural plasticity that allows folding into a SH2-like domain in the presence of phosphotyrosine ligands. Using protein-protein interaction assays, we demonstrated that both SH2 and GEF domains of GIV are required for the formation of a ligand-activated ternary complex between GIV, Gαi, and growth factor receptors and for activation of Gαi after growth factor stimulation. Expression of a SH2-deficient GIV mutant (Arg 1745→Leu) that cannot bind RTKs impaired all previously demonstrated functions of GIV-Akt enhancement, actin remodeling, and cell migration. The mechanistic and structural insights gained here shed light on the long-standing questions surrounding RTK/G protein cross-talk, set a novel paradigm, and characterize a unique pharmacological target for uncoupling GIV-dependent signaling downstream of multiple oncogenic RTKs.

Toward directed reprogramming through exogenous factors.

Direct reprogramming of one cell type into another provides unprecedented opportunities to study fundamental biology, model disease, and develop regenerative medicine. Different paradigms of reprogramming strategies with different sets of factors have been developed to generate various cell types, including induced pluripotent stem cells, neuronal or neural precursor cells, cardiomyocyte-like cells, endothelial cells, and hepatocyte-like cells. Various exogenous factors, especially small molecules modulating signaling, cellular state, and transcription, have been identified to enhance and enable reprogramming. With an increased understanding of reprogramming mechanisms and discovery of new molecules, it is conceivable that reprogramming can be achieved in a more directed and deterministic manner under entirely chemically defined conditions.