Overcoming retinoic acid resistance in HER2-enriched breast cancers: role of MYC.

HER2-enriched (HER2+) breast cancers express high levels of the growth-promoting HER2 protein. Although these cancers are treated with the HER2-targeted drug, trastuzumab, resistance to treatment is common. Retinoic acid (RA) is an anti-cancer agent that has been successfully used for the treatment of leukemia and holds promise for the treatment of solid cancers, including breast cancer. The HER2 gene is frequently co-amplified with RARA, a key determinant of RA sensitivity in breast cancers. It seems surprising, therefore, that HER2+ breast cancers are refractory to RA treatment. Here, we show that MYC mediates RA resistance by suppressing the expression of cellular retinoic acid binding protein 2 (CRABP2), resulting in RARα inactivation. CRABP2 is an intracellular RA transporter that delivers RA to the nuclear receptor RARα for its activation. Our results indicate that response to RA is enhanced by MYC depletion in HER2+ breast cancer cells and that RA treatment enhances trastuzumab responsiveness. Our findings support the use of RA and trastuzumab for the treatment of subsets of patients with breast cancers that are HER2-RARα co-amplified and have low levels of MYC.

Stationary-to-migratory transition in glioblastoma stem-like cells driven by a fatty acid-binding protein 7-RXRα neurogenic pathway.

BACKGROUND: Glioblastoma (GBM) stem-like cells (GSCs) are crucial drivers of treatment resistance and tumor recurrence. While the concept of "migrating" cancer stem cells was proposed a decade ago, the roles and underlying mechanisms of the heterogeneous populations of GSCs remain poorly defined. METHODS: Cell migration using GBM cell lines and patient-derived GSCs was examined using Transwell inserts and the scratch assay. Single-cell RNA sequencing data analysis were used to map GSC drivers to specific GBM cell populations. Xenografted mice were used to model the role of brain-type fatty acid-binding protein 7 (FABP7) in GBM infiltration and expansion. The mechanism by which FABP7 and its fatty acid ligands promote GSC migration was examined by gel shift and luciferase gene reporter assays. RESULTS: A subpopulation of FABP7-expressing migratory GSCs was identified, with FABP7 upregulating SOX2, a key modulator for GBM stemness and plasticity, and ZEB1, a prominent factor in GBM epithelial-mesenchymal transition and invasiveness. Our data indicate that GSC migration is driven by nuclear FABP7 through activation of RXRα, a nuclear receptor activated by polyunsaturated fatty acids (PUFAs). CONCLUSION: Infiltrative progression in GBM is driven by migratory GSCs through activation of a PUFA-FABP7-RXRα neurogenic pathway.

RNA cytosine methyltransferase NSUN5 promotes protein synthesis and tumorigenic phenotypes in glioblastoma.

Glioblastoma (GBM) is the most common and aggressive malignant primary brain tumor in adults. The standard treatment achieves a median overall survival for GBM patients of only 15 months. Hence, novel therapies based on an increased understanding of the mechanistic underpinnings of GBM are desperately needed. In this study, we show that elevated expression of 28S rRNA (cytosine-C(5))-methyltransferase NSUN5, which methylates cytosine 3782 of 28S rRNA in GBM cells, is strongly associated with the poor survival of GBM patients. Moreover, we demonstrate that overexpression of NSUN5 increases protein synthesis in GBM cells. NSUN5 knockdown decreased protein synthesis, cell proliferation, sphere formation, migration, and resistance to temozolomide in GBM cell lines. NSUN5 knockdown also decreased the number and size of GBM neurospheres in vitro. As a corollary, mice harboring U251 tumors wherein NSUN5 was knocked down survived longer than mice harboring control tumors. Taken together, our results suggest that NSUN5 plays a protumorigenic role in GBM by enabling the enhanced protein synthesis requisite for tumor progression. Accordingly, NSUN5 may be a hitherto unappreciated target for the treatment of GBM.

Point-of-care ultrasound diagnosis of skull fracture in Chinese children 0-6 years old with scalp hematoma from minor head trauma: A preliminary prospective observational study.

Background: Previous studies have suggested that point-of-care ultrasound could help to evaluate and diagnose pediatric skull fracture for the closed scalp hematoma from blunt trauma. However, relevant data in Chinese children are missing, especially in children 0-6 years old. Objectives: Our study aimed to evaluate the efficacy of point-of-care ultrasound to diagnose skull fracture in children 0-6 years old with scalp hematoma in China. Methods: We performed a prospective observational study and screened children 0-6 years old with closed scalp hematoma and a Glasgow coma scale of 14-15 at Hospital in China. Enrolled children (N = 152) were first evaluated for skull fracture with point-of-care ultrasound by the emergency physician and then received a head computed tomography scan. Results: The point-of-care ultrasound examination and computed tomography scan revealed skull fracture in 13 (8.6%) and 12 (7.9%) children, respectively. The kappa test showed a satisfactory agreement between two examinations (P < 0.0001), with kappa = 0.87 (95% confidence interval, i.e., 95% CI, [0.69, 1.00]) and area under the curve = 0.95 (95% CI [0.86, 1], P < 0.0001). The point-of-care ultrasound examination had the sensitivity of 91.7% (95% CI [62.5%, 100%]), specificity of 98.6% (95% CI [94.6%, 100%]), positive predictive value of 84.6% (95% CI [56.5%, 96.9%]), negative predictive value of 99.2% (95% CI [95.6%, 100%]), and accuracy of 98.0% (95% CI [94.1%, 99.6%]). Conclusions: While our study is preliminary in nature, our findings may guide future larger studies in assessing the utility of point-of-care ultrasound examination in diagnosing skull fractures in children with scalp hematoma from minor head trauma.

Analysis of verification results of protective effects of hearing protectors in different industries / 中华劳动卫生职业病杂志

Objective: To get insight into the current practice of noise reduction effect of workers as they wore hearing protectors in different domestic enterprises and the possible affected factors. Methods: From October 2020 to April 2021, using a random sampling method, 1197 workers exposed to noise in petrochemical factories, textile factories, and parts manufacturing factories were selected as the study subjects. The noise reduction effect of hearing protectors worn by workers in daily use was tested using a hearing protector suitability testing system. The personal sound attenuation level (PAR) was compared among workers in three enterprises, Targeted intervention and repetitive testing were conducted for workers who did not meet the noise reduction effect required by the enterprise, and the changes in PAR of workers before and after the intervention were compared. The comparison of baseline PARs between two or more groups was performed using the Mann Whitney test, the comparison of baseline PARs with post intervention PARs was performed using the Wilcoxon signed rank sum test, and the comparison of qualitative data between two or more groups was performed using the Chi square test. Results: The median baseline PAR for all workers was 15 dB. Men, age<30 years old, education level at or above college level, working experience of 5 to 15 years, and those who used hearing protectors for 5 to 15 years had higher PARs, with statistically significant differences (P<0.05). The median difference in baseline PAR among workers from three enterprises was statistically significant (H=175.06, P<0.01). The median PAR of subjects who did not pass the baseline increased from 3 dB to 21 dB after intervention (Z=-27.92, P<0.01) . Conclusion: Some workers wearing hearing protectors do not meet the required PAR, and low PARs may be related to incorrect wearing methods and incorrect selection of hearing protectors. As a tool for testing, training, and assisting in selection, the hearing protector suitability testing system is of great significance for worker hearing protection.

Investigation on skills of using dust mask in dust-exposed workers of civil metal ship manufacturing enterprises / 中国职业医学

OBJECTIVE: To analyze the skills of using dust mask in the dust-exposed workers in civil metal ship manufacturing enterprises. METHODS: A total of 123 dust-exposed workers in a civil metal ship manufacturing enterprise were selected as the research subjects using convenience sampling method. Dust Mask Using Situation and Maintenance Questionnaire was used to investigate the use of dust masks, and the tightness of using dust mask was measured by the tightness tester. RESULTS: The median, and the 0 th-100 th percentiles[M(P_0-P_(100))] of the dust mask use time in the workers was 3.0(1.0-3.0) months, and the M(P_0-P_(100)) of filter element use time was 1.0(0.5-2.0) workdays. The subjects did not disinfect the masks after use. Only 36.6%(45/123) of workers regularly cleaned dust masks during use. There was 62.6%(77/123) of workers who failed to correctly perform negative pressure air tightness check by themselves. A total of 112 workers carried out tightness test, and the pass rate of those who passed the tightness test for the first time was 62.5%(70/112). The median, and the 25 th and 75 th percentiles [M(P_(25), P_(75))] of fit factor(FF) in the 70 qualified workers was 835.0(503.0, 1 635.0). After retests, the overall tightness test pass rate was 66.1%(74/112), and the M(P_(25), P_(75)) of FF in the 74 qualified workers was 786.0(477.7, 1 532.2). The reasons for failure of tightness test were the mismatch of the mask and face size, wrong wearing methods and long beard. CONCLUSION: Some of the dust-exposed workers in the civil metal ship manufacturing enterprises did not use the dust mask correctly. The dust mask configuration and the use and maintenance training should be strengthened, and the tightness test should be carried out regularly to improve workers′ skills in using dust masks.

Research progress on verification methods on measuring noise attenuation value of hearing protective devices / 中国职业医学

At present, the methods for verifying the attenuation of hearing protective devices(HPDs) mainly include real-ear attenuation at threshold(REAT), microphone in real ear(MIRE), and acoustical test fixture(ATF). Among them, the REAT is the gold standard, but its testing requirements are strict and there is a physiological noise masking effect. The test results of MIRE need to be modified by transfer function of the open ear, which has the advantage of convenient operation without being affected by subjective feelings. The ATF method is mainly used to verify the shape and quality of customized HPDs since its artificial ear design cannot truly reflect the real-ear test situation. The HPD fit testing has been well developed and widely applied abroad, which has been proved to be able to accurately verify and effectively improve the attenuation of workers wearing HPDs. However, relevant research and applications have only been carried out in China in recent years. At present, the main problems in the verification of the protective effect of HPDs in China are as follows: firstly, the measurement is only limited in attenuation and fail to comprehensively consider the applicability and comfort of the HPDs; secondly, a-weighted sound pressure level is mostly used in noise monitoring in China, while the choice of HPDs is based on C-weighted-sound pressure level. The transition between these two has not been established. Future research should be devoted to solve the above problems and help the use of HPDs in preventing the hearing loss of noise-exposed workers.

Heart sound classification based on sub-band envelope and convolution neural network / 生物医学工程学杂志

Automatic classification of heart sounds plays an important role in the early diagnosis of congenital heart disease. A kind of heart sound classification algorithms based on sub-band envelope feature and convolution neural network was proposed in this paper, which did not need to segment the heart sounds according to cardiac cycle accurately. Firstly, the heart sound signal was divided into some frames. Then, the frame level heart sound signal was filtered with Gammatone filter bank to obtain the sub-band signals. Next, the sub-band envelope was extracted by Hilbert transform. After that, the sub-band envelope was stacked into a feature map. Finally, type Ⅰ and type Ⅱ convolution neural network were selected as classifier. The result shown that the sub-band envelope feature was better in type Ⅰ than type Ⅱ. The algorithm is tested with 1 000 heart sound samples. The test results show that the overall performance of the algorithm proposed in this paper is significantly improved compared with other similar algorithms, which provides a new method for automatic classification of congenital heart disease, and speeds up the process of automatic classification of heart sounds applied to the actual screening.

An Amplified Fatty Acid-Binding Protein Gene Cluster in Prostate Cancer: Emerging Roles in Lipid Metabolism and Metastasis.

Treatment for early stage and localized prostate cancer (PCa) is highly effective. Patient survival, however, drops dramatically upon metastasis due to drug resistance and cancer recurrence. The molecular mechanisms underlying PCa metastasis are complex and remain unclear. It is therefore crucial to decipher the key genetic alterations and relevant molecular pathways driving PCa metastatic progression so that predictive biomarkers and precise therapeutic targets can be developed. Through PCa cohort analysis, we found that a fatty acid-binding protein (FABP) gene cluster (containing five FABP family members) is preferentially amplified and overexpressed in metastatic PCa. All five FABP genes reside on chromosome 8 at 8q21.13, a chromosomal region frequently amplified in PCa. There is emerging evidence that these FABPs promote metastasis through distinct biological actions and molecular pathways. In this review, we discuss how these FABPs may serve as drivers/promoters for PCa metastatic transformation using patient cohort analysis combined with a review of the literature.

S100A10 Has a Critical Regulatory Function in Mammary Tumor Growth and Metastasis: Insights Using MMTV-PyMT Oncomice and Clinical Patient Sample Analysis.

S100A10 (p11) is a plasminogen receptor that regulates cellular plasmin generation by cancer cells. In the current study, we used the MMTV-PyMT mouse breast cancer model, patient tumor microarray, and immunohistochemical (IHC) analysis to investigate the role of p11 in oncogenesis. The genetic deletion of p11 resulted in significantly decreased tumor onset, growth rate, and spontaneous pulmonary metastatic burden in the PyMT/p11-KO (knock-out) mice. This phenotype was accompanied by substantial reduction in Ki67 positivity, macrophage infiltration, decreased vascular density in the primary tumors, and decrease in invasive carcinoma and pulmonary metastasis. Surprisingly, IHC analysis of wild-type MMTV-PyMT mice failed to detect p11 expression in the tumors or metastatic tumor cells and loss of p11 did not decrease plasmin generation in the PyMT tumors and cells. Furthermore, tumor cells expressing p11 displayed dramatically reduced lung metastasis when injected into p11-depleted mice, further strengthening the stromal role of p11 in tumor growth and metastasis. Transcriptome analysis of the PyMT tumors from p11-KO mice showed marked reduction in genes such as Areg, Muc1, and S100a8 involved in breast cancer development, progression, and inflammation. The PyMT/p11-KO tumors displayed a remarkable increase in inflammatory cytokines such as interleukin (Il)-6, Il-10, and interferon (Ifn)-γ. Gene expression profiling and IHC of primary breast cancer samples showed that p11 mRNA and protein levels were significantly higher in tumor tissues compared to normal mammary tissue. P11 mRNA expression was significantly associated with poor patient prognosis and significantly elevated in high grade, triple negative (TN) tumors, and tumors with high proliferative index. This is the first study examining the crucial role of p11 in breast tumor development and metastasis, thus emphasizing its potential as a diagnostic and prognostic biomarker in breast cancer.

The FABP12/PPARγ pathway promotes metastatic transformation by inducing epithelial-to-mesenchymal transition and lipid-derived energy production in prostate cancer cells.

Early stage localized prostate cancer (PCa) has an excellent prognosis; however, patient survival drops dramatically when PCa metastasizes. The molecular mechanisms underlying PCa metastasis are complex and remain unclear. Here, we examine the role of a new member of the fatty acid-binding protein (FABP) family, FABP12, in PCa progression. FABP12 is preferentially amplified and/or overexpressed in metastatic compared to primary tumors from both PCa patients and xenograft animal models. We show that FABP12 concurrently triggers metastatic phenotypes (induced epithelial-to-mesenchymal transition (EMT) leading to increased cell motility and invasion) and lipid bioenergetics (increased fatty acid uptake and accumulation, increased ATP production from fatty acid ß-oxidation) in PCa cells, supporting increased reliance on fatty acids for energy production. Mechanistically, we show that FABP12 is a driver of PPARγ activation which, in turn, regulates FABP12's role in lipid metabolism and PCa progression. Our results point to a novel role for a FABP-PPAR pathway in promoting PCa metastasis through induction of EMT and lipid bioenergetics.

Segmentation of heart sound signals based on duration hidden Markov model / 生物医学工程学杂志

Heart sound segmentation is a key step before heart sound classification. It refers to the processing of the acquired heart sound signal that separates the cardiac cycle into systolic and diastolic, etc. To solve the accuracy limitation of heart sound segmentation without relying on electrocardiogram, an algorithm based on the duration hidden Markov model (DHMM) was proposed. Firstly, the heart sound samples were positionally labeled. Then autocorrelation estimation method was used to estimate cardiac cycle duration, and Gaussian mixture distribution was used to model the duration of sample-state. Next, the hidden Markov model (HMM) was optimized in the training set and the DHMM was established. Finally, the Viterbi algorithm was used to track back the state of heart sounds to obtain S

NFIB promotes cell survival by directly suppressing p21 transcription in TP53-mutated triple-negative breast cancer.

Triple-negative breast cancer (TNBC) is an aggressive breast cancer subtype with limited treatment options and poor prognosis. There is an urgent need to identify and understand the key factors and signalling pathways driving TNBC tumour progression, relapse, and treatment resistance. In this study, we report that gene copy numbers and expression levels of nuclear factor IB (NFIB), a recently identified oncogene in small cell lung cancer, are preferentially increased in TNBC compared to other breast cancer subtypes. Furthermore, increased levels of NFIB are significantly associated with high tumour grade, poor prognosis, and reduced chemotherapy response. Concurrent TP53 mutations and NFIB overexpression (z-scores > 0) were observed in 77.9% of TNBCs, in contrast to 28.5% in non-TNBCs. Depletion of NFIB in TP53-mutated TNBC cell lines promotes cell death, cell cycle arrest, and enhances sensitivity to docetaxel, a first-line chemotherapeutic drug in breast cancer treatment. Importantly, these alterations in growth properties were accompanied by induction of CDKN1A, the gene encoding p21, a downstream effector of p53. We show that NFIB directly interacts with the CDKN1A promoter in TNBC cells. Furthermore, knockdown of combined p21 and NFIB reverses the docetaxel-induced cell growth inhibition observed upon NFIB knockdown, indicating that NFIB's effect on chemotherapeutic drug response is mediated through p21. Our results indicate that NFIB is an important TNBC factor that drives tumour cell growth and drug resistance, leading to poor clinical outcomes. Thus, targeting NFIB in TP53-mutated TNBC may reverse oncogenic properties associated with mutant p53 by restoring p21 activity. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Classification of heart sound signals in congenital heart disease based on convolutional neural network / 生物医学工程学杂志

Cardiac auscultation is the basic way for primary diagnosis and screening of congenital heart disease(CHD). A new classification algorithm of CHD based on convolution neural network was proposed for analysis and classification of CHD heart sounds in this work. The algorithm was based on the clinically collected diagnosed CHD heart sound signal. Firstly the heart sound signal preprocessing algorithm was used to extract and organize the Mel Cepstral Coefficient (MFSC) of the heart sound signal in the one-dimensional time domain and turn it into a two-dimensional feature sample. Secondly, 1 000 feature samples were used to train and optimize the convolutional neural network, and the training results with the accuracy of 0.896 and the loss value of 0.25 were obtained by using the Adam optimizer. Finally, 200 samples were tested with convolution neural network, and the results showed that the accuracy was up to 0.895, the sensitivity was 0.910, and the specificity was 0.880. Compared with other algorithms, the proposed algorithm has improved accuracy and specificity. It proves that the proposed method effectively improves the robustness and accuracy of heart sound classification and is expected to be applied to machine-assisted auscultation.

[Case-control study on polymer polylactic acid absorbable medical film for preventing acromion adhesion after arthroscopic rotator cuff repair].

OBJECTIVE: To study effect of shoulder joint function after rotator cuff repair of polylactic acid absorbable membrane. METHODS: From September 2015 to December 2016, 50 patients diagnosed with rotator cuff tear were selected and divided into treatment group and control group. There were 25 patients in control group, including 12 males and 13 females, with an average age of (48.7±3.5) years old, who received simple arthroscopic rotator cuff repair. There were 25 patients in treatment group, including 11 males and 14 females, with an average age of(49.2±4.1) years old, who performed arthroscopic rotator cuff repair with implanting polylactic acid absorbable membraneon shoulder of rotator cuff. Preoperative and postoperative VAS score, ASES score and UCLA score were recorded and compared between two groups. RESULTS: At 6 months after operation, preoperative VAS score in control group was 5.48±1.12, and decreased as 1.28±0.84 after operation; ASES score before operation was 52.24±4.64, and improved to 86.92±3.20 after operation;preoperative UCLA score improved from 14.36±1.89 before operation to 30.72±1.28 after operation. In treatment group, VAS score decreased from 5.36±1.32 before operation to 1.40±0.71 after operation;preoperative ASES score was 51.04±4.09, and improved to 88.96±2.79 after operation; UCLA score improved from 15.12±1.81 before operation to 32.12±1.33 after operation. There was no significant difference in VAS score between two groups, and ASES score, UCLA score in treatment group was obviously better than control group. CONCLUSIONS: Application of polylactic acid absorbable medical membrane could obviously improve shoulder function, and effectively prevent acromion adhesion after arthroscopic rotator cuff repair.

Case-control study on polymer polylactic acid absorbable medical film for preventing acromion adhesion after arthroscopic rotator cuff repair / 中国骨伤

<p><b>OBJECTIVE</b>To study effect of shoulder joint function after rotator cuff repair of polylactic acid absorbable membrane.</p><p><b>METHODS</b>From September 2015 to December 2016, 50 patients diagnosed with rotator cuff tear were selected and divided into treatment group and control group. There were 25 patients in control group, including 12 males and 13 females, with an average age of (48.7±3.5) years old, who received simple arthroscopic rotator cuff repair. There were 25 patients in treatment group, including 11 males and 14 females, with an average age of(49.2±4.1) years old, who performed arthroscopic rotator cuff repair with implanting polylactic acid absorbable membraneon shoulder of rotator cuff. Preoperative and postoperative VAS score, ASES score and UCLA score were recorded and compared between two groups.</p><p><b>RESULTS</b>At 6 months after operation, preoperative VAS score in control group was 5.48±1.12, and decreased as 1.28±0.84 after operation; ASES score before operation was 52.24±4.64, and improved to 86.92±3.20 after operation;preoperative UCLA score improved from 14.36±1.89 before operation to 30.72±1.28 after operation. In treatment group, VAS score decreased from 5.36±1.32 before operation to 1.40±0.71 after operation;preoperative ASES score was 51.04±4.09, and improved to 88.96±2.79 after operation; UCLA score improved from 15.12±1.81 before operation to 32.12±1.33 after operation. There was no significant difference in VAS score between two groups, and ASES score, UCLA score in treatment group was obviously better than control group.</p><p><b>CONCLUSIONS</b>Application of polylactic acid absorbable medical membrane could obviously improve shoulder function, and effectively prevent acromion adhesion after arthroscopic rotator cuff repair.</p>

Oxidative stress contributes to the tamoxifen-induced killing of breast cancer cells: implications for tamoxifen therapy and resistance.

Tamoxifen is the accepted therapy for patients with estrogen receptor-α (ERα)-positive breast cancer. However, clinical resistance to tamoxifen, as demonstrated by recurrence or progression on therapy, is frequent and precedes death from metastases. To improve breast cancer treatment it is vital to understand the mechanisms that result in tamoxifen resistance. This study shows that concentrations of tamoxifen and its metabolites, which accumulate in tumors of patients, killed both ERα-positive and ERα-negative breast cancer cells. This depended on oxidative damage and anti-oxidants rescued the cancer cells from tamoxifen-induced apoptosis. Breast cancer cells responded to tamoxifen-induced oxidation by increasing Nrf2 expression and subsequent activation of the anti-oxidant response element (ARE). This increased the transcription of anti-oxidant genes and multidrug resistance transporters. As a result, breast cancer cells are able to destroy or export toxic oxidation products leading to increased survival from tamoxifen-induced oxidative damage. These responses in cancer cells also occur in breast tumors of tamoxifen-treated mice. Additionally, high levels of expression of Nrf2, ABCC1, ABCC3 plus NAD(P)H dehydrogenase quinone-1 in breast tumors of patients at the time of diagnosis were prognostic of poor survival after tamoxifen therapy. Therefore, overcoming tamoxifen-induced activation of the ARE could increase the efficacy of tamoxifen in treating breast cancer.

Association between cytoplasmic CRABP2, altered retinoic acid signaling, and poor prognosis in glioblastoma.

Retinoic acid (RA), a metabolite of vitamin A, is required for the regulation of growth and development. Aberrant expression of molecules involved in RA signaling has been reported in various cancer types including glioblastoma multiforme (GBM). Cellular retinoic acid-binding protein 2 (CRABP2) has previously been shown to play a key role in the transport of RA to retinoic acid receptors (RARs) to activate their transcription regulatory activity. Here, we demonstrate that CRABP2 is predominantly located in the cytoplasm of GBM tumors. Cytoplasmic, but not nuclear, CRABP2 levels in GBM tumors are associated with poor patient survival. Treatment of malignant glioma cell lines with RA results in a dose-dependent increase in accumulation of CRABP2 in the cytoplasm. CRABP2 knockdown reduces proliferation rates of malignant glioma cells, and enhances RA-induced RAR activation. Levels of CRYAB, a small heat shock protein with anti-apoptotic activity, and GFAP, an astrocyte-specific intermediate filament protein, are greatly reduced in CRABP2-depleted cells. Restoration of CRYAB expression partially but significantly reversed the effect of CRABP2 depletion on RAR activation. Our combined in vivo and in vitro data indicate that: (i) CRABP2 is an important determinant of clinical outcome in GBM patients, and (ii) the mechanism of action of CRABP2 in GBM involves sequestration of RA in the cytoplasm and activation of an anti-apoptotic pathway, thereby enhancing proliferation and preventing RA-mediated cell death and differentiation. We propose that reducing CRABP2 levels may enhance the therapeutic index of RA in GBM patients.

CRABP1 is associated with a poor prognosis in breast cancer: adding to the complexity of breast cancer cell response to retinoic acid.

BACKGROUND: Clinical trials designed to test the efficacy of retinoic acid (RA) as an adjuvant for the treatment of solid cancers have been disappointing, primarily due to RA resistance. Estrogen receptor (ER)-negative breast cancer cells are more resistant to RA than ER-positive cells. The expression and subcellular distribution of two RA-binding proteins, FABP5 and CRABP2, has already been shown to play critical roles in breast cancer cell response to RA. CRABP1, a third member of the RA-binding protein family, has not previously been investigated as a possible mediator of RA action in breast cancer. METHODS: CRABP1 and CRABP2 expression in primary breast tumor tissues was analyzed using gene expression and tissue microarrays. CRABP1 levels were manipulated using siRNAs and by transient overexpression. RA-induced subcellular translocation of CRABPs was examined by immunofluorescence microscopy and immunoblotting. RA-induced transactivation of RAR was analyzed using a RA response element (RARE)-driven luciferase reporter system. Effects of CRABP1 expression and RA treatment on downstream gene expression were investigated by semi-quantitative RT-PCR analysis. RESULTS: Compared to normal mammary tissues, CRABP1 expression is significantly down-regulated in ER+ breast tumors, but maintained in triple-negative breast cancers. Elevated CRABP1 levels are associated with poor patient prognosis, high Ki67 immunoreactivity and high tumor grade in breast cancer. The prognostic significance of CRABP1 is attributed to its cytoplasmic localization. We demonstrate that CRABP1 expression attenuates RA-induced cell growth arrest and inhibits RA signalling in breast cancer cells by sequestering RA in the cytoplasm. We also show that CRABP1 affects the expression of genes involved in RA biosynthesis, trafficking and metabolism. CONCLUSIONS: CRABP1 is an adverse factor for clinical outcome in triple-negative breast cancer and a potent inhibitor of RA signalling in breast cancer cells. Our data indicate that CRABP1, in conjunction with previously identified CRABP2 and FABP5, plays a key role in breast cancer cell response to RA. We propose that these three RA-binding proteins can serve as biomarkers for predicting triple-negative breast cancer response to RA, with elevated levels of either cytoplasmic CRABP1 or FABP5 associated with RA resistance, and elevated levels of nuclear CRABP2 associated with sensitivity to RA.