Low-loss tantalum pentoxide photonics with a CMOS-compatible process.

We report a Ta2O5 photonic platform with a propagation loss of 0.49 dB/cm at 1550 nm, of 0.86 dB/cm at 780 nm, and of 3.76 dB/cm at 2000 nm. The thermal bistability measurement is conducted in the entire C-band for the first time to reveal the absorption loss of Ta2O5 waveguides, offering guidelines for further reduction of the waveguide loss. We also characterize the Ta2O5 waveguide temperature response, which shows favorable thermal stability. The fabrication process temperature is below 350°C, which is friendly to integration with active optoelectronic components.

BRCA1-Mediated Dual Regulation of Ferroptosis Exposes a Vulnerability to GPX4 and PARP Co-Inhibition in BRCA1-Deficient Cancers.

Resistance to poly (ADP-ribose) polymerase inhibitors (PARPi) limits the therapeutic efficacy of PARP inhibition in treating breast cancer susceptibility gene 1 (BRCA1)-deficient cancers. Here we reveal that BRCA1 has a dual role in regulating ferroptosis. BRCA1 promotes the transcription of voltage-dependent anion channel 3 (VDAC3) and glutathione peroxidase 4 (GPX4); consequently, BRCA1 deficiency promotes cellular resistance to erastin-induced ferroptosis but sensitizes cancer cells to ferroptosis induced by GPX4 inhibitors (GPX4i). In addition, nuclear receptor coactivator 4 (NCOA4)-mediated ferritinophagy and defective GPX4 induction unleash potent ferroptosis in BRCA1-deficient cancer cells upon PARPi and GPX4i co-treatment. Finally, we show that xenograft tumors derived from patients with BRCA1-mutant breast cancer with PARPi resistance exhibit decreased GPX4 expression and high sensitivity to PARP and GPX4 co-inhibition. Our results show that BRCA1 deficiency induces a ferroptosis vulnerability to PARP and GPX4 co-inhibition and inform a therapeutic strategy for overcoming PARPi resistance in BRCA1-deficient cancers. Significance: BRCA1 deficiency promotes resistance to erastin-induced ferroptosis via blocking VDAC3 yet renders cancer cells vulnerable to GPX4i-induced ferroptosis via inhibiting GPX4. NCOA4 induction and defective GPX4 further synergizes GPX4i with PARPi to induce ferroptosis in BRCA1-deficient cancers and targeting GPX4 mitigates PARPi resistance in those cancers. See related commentary by Alborzinia and Friedmann Angeli, p. 1372.

Knockdown of let-7b in leukemia associated macrophages inhibit acute myeloid leukemia progression.

Macrophages, critical components of bone marrow microenvironment, are reported to be remodeled into leukemia-associated macrophages (LAMs) in leukemic microenvironment where they contribute to leukemia development, characterized as M2 macrophages with pro-tumor effects. However, how leukemic microenvironment transforms macrophages into LAMs remains unknown. Here, we analyzed the clinical relevance of LAMs and profiled their RNA-Seq from acute myeloid leukemia (AML) patients with complete remission (CR) after induction treatment and refractory AML patients. Our results showed that the proportion and number of LAMs in refractory AML patients was higher than that in CR patients and LAM was a poor prognostic factor of AML patients. Furthermore, let-7b was a potentially aberrant gene in LAMs contributed to M2-subtype characteristics. Knockdown of let-7b in LAMs could inhibit the development of AML by repolarizing LAMs toward M1-subtype characteristics through the activation of Toll-like receptor and NF-κB pathway. Our study provides insight for future LAM-based immunotherapy strategies for AML.

A retrospective analysis of EBV-DNA status with the prognosis of lymphoma.

Epstein-Barr virus (EBV) infection is proved to be associated with clinicopathology of lymphoma. However, little is known about the relationship between EBV-DNA status after treatment and prognosis. In this study, real-time polymerase chain reaction (PCR) was used for quantitative detection of EBV-DNA load in peripheral blood of all 26,527 patients with lymphoma, and the clinical characteristics and prognosis of 202 patients were retrospectively analysed, including 100 patients with positive EBV-DNA and 102 randomly selected patients with negative EBV-DNA. We found that the average rate of EBV-DNA positivity in lymphomas was 0.376%, and EBV-DNA-positive patients presented higher risk with elevated lactate dehydrogenase (LDH) and ß2-MG level, B symptoms, secondary hemophagocytic syndrome and lower objective response rate compared to EBV-DNA-negative patients. Multivariate analysis revealed EBV-DNA-positive patients had inferior progression-free survival (PFS) and overall survival (OS) and EBV-DNA level before treatment was related to PFS but not OS of T/NK cell lymphoma. In T/NK cell lymphoma, EBV-DNA converting negative after treatment was correlated with better PFS but not OS, and second-line therapy could induce more EBV-DNA-negative conversion compared to CHOP-based therapy. In all, EBV-DNA positivity before treatment can be a biomarker representing the tumour burden and an independent prognostic factor. EBV-DNA-negative conversion after treatment is a good prognostic factor for T/NK cell lymphomas.

Somatic Trp53 mutations differentially drive breast cancer and evolution of metastases.

TP53 mutations are the most frequent genetic alterations in breast cancer and are associated with more aggressive disease and worse overall survival. We have created two conditional mutant Trp53 alleles in the mouse that allow expression of Trp53R172H or Trp53R245W missense mutations in single cells surrounded by a normal stroma and immune system. Mice with Trp53 mutations in a few breast epithelial cells develop breast cancers with high similarity to human breast cancer including triple negative. p53R245W tumors are the most aggressive and exhibit metastases to lung and liver. Development of p53R172H breast tumors with some metastases requires additional hits. Sequencing of primary tumors and metastases shows p53R245W drives a parallel evolutionary pattern of metastases. These in vivo models most closely simulate the genesis of human breast cancer and will thus be invaluable in testing novel therapeutic options.

MicroRNA-494 Activation Suppresses Bone Marrow Stromal Cell-Mediated Drug Resistance in Acute Myeloid Leukemia Cells.

Acute myeloid leukemia (AML) is not sensitive to chemotherapy partially because of the protection of AML cells by mesenchymal stromal cells (MSCs). Our previous studies found that MSCs protected AML cells from apoptosis through the c-Myc-dependent pathway. However, the mechanism by which MSCs regulate c-Myc in AML cells is still unknown. To elucidate the mechanism, we performed microRNA array analysis of AML cell lines and validated by TaqMan realtime PCR. The results showed that the expression of microRNA-494 (miR-494) in AML cells after coculture with MSCs was downregulated. Reporter gene analysis confirmed miR-494 as one of the regulators of c-Myc. In the coculture system, activation of miR-494 in AML cells suppressed proliferation and induced apoptosis of AML cells in vitro. After addition of mitoxantrone to the coculture system, the proliferation of AML cells with miR-494 activation was suppressed more than that of control cells. After subcutaneous injection of AML cell lines in combination with MSC, tumor growth was suppressed in mice injected with miR-494-overexpressing AML cells. The rate of tumor formation was even lower after mitoxantrone treatment in the miR-494 overexpressing group. Moreover, miR-494 activation resulted in a decrease of leukemic cell counts in peripheral blood (PB) and bone marrow, and prolonged survival in mice injected with miR-494-overexpressing AML cellls and MSCs compared to the control mice. Our results indicate that miR-494 suppresses drug resistance in AML cells by downregulating c-Myc through interaction with MSCs and that miR-494 therefore is a potential therapeutic target. J. Cell. Physiol. 232: 1387-1395, 2017. © 2016 Wiley Periodicals, Inc.

SENP1 promotes proliferation of clear cell renal cell carcinoma through activation of glycolysis.

Metabolic shift toward aerobic glycolysis is a fundamental element contributing to the development and progression of clear cell renal cell carcinoma (ccRCC). We and others previously observed enhanced glycolysis and diminished tricarboxylic acid (TCA) cycle activity in ccRCC tissue. Here, by integrated gene expression and metabolomic analyses of 36 matched pairs of tumor and adjacent normal tissues, we showed that expression of Sentrin/SUMO-specific protease 1 (SENP1) is positively associated with glycolysis levels in ccRCC. Moreover, SENP1 knockdown in RCC4/VHL cells downregulated expression of key glycolytic enzymes under normoxic and hypoxic conditions and inhibited cell proliferation under hypoxic conditions, possibly due to ineffective deSUMOylation and stablization of Hif-1α related to the SENP-1 deficiency. Finally, SENP1 expression correlated positively with tumor pathological grade and was an indicator of poor overall survival and advanced tumor progression in ccRCC. Altered VHL gene function is found in 60-90% ccRCC cases of ccRCC, but therapies targeting VHL-related signaling pathways have been ineffective, spurring exploration of alternative pathological signaling events. Our results provide a possible mechanistic explanation for the role of SENP1 in the initiation and development of ccRCC with normal VHL activity, and identifies SENP1 as a potential treatment target for the disease.

Tissue-specific and age-dependent effects of global Mdm2 loss.

Mdm2, an E3 ubiquitin ligase, negatively regulates the tumour suppressor p53. In this study we utilized a conditional Mdm2 allele, Mdm2(FM) , and a CAG-CreER tamoxifen-inducible recombination system to examine the effects of global Mdm2 loss in adult mice. Two different tamoxifen injection regimens caused 100% lethality of Mdm2(FM) (/-) ;CAG-CreER mice; both radio-sensitive and radio-insensitive tissues were impaired. Strikingly, a large number of radio-insensitive tissues, including the kidney, liver, heart, retina and hippocampus, exhibited various pathological defects. Similar tamoxifen injections in older (16-18 month-old) Mdm2(FM) (/-) ;CAG-CreER mice yielded abnormalities only in the kidney. In addition, transcriptional activation of Cdkn1a (p21), Bbc3 (Puma) and multiple senescence markers in young (2-4 month-old) mice following loss of Mdm2 was dampened in older mice. All phenotypes were p53-dependent, as Mdm2(FM) (/-) ;Trp53(-/-) ;CAG-CreER mice subjected to the same tamoxifen regimens were normal. Our findings implicate numerous possible toxicities in many normal tissues upon use of cancer therapies that aim to inhibit Mdm2 in tumours with wild-type p53.

Acute T-cell leukemias remain dependent on Notch signaling despite PTEN and INK4A/ARF loss.

NOTCH1 is activated by mutation in more than 50% of human T-cell acute lymphoblastic leukemias (T-ALLs) and inhibition of Notch signaling causes cell-cycle/growth arrest, providing rationale for NOTCH1 as a therapeutic target. The tumor suppressor phosphatase and tensin homolog (PTEN) is also mutated or lost in up to 20% of cases. It was recently observed among human T-ALL cell lines that PTEN loss correlated with resistance to Notch inhibition, raising concern that patients with PTEN-negative disease may fail Notch inhibitor therapy. As these studies were limited to established cell lines, we addressed this issue using a genetically defined mouse retroviral transduction/bone marrow transplantation model and observed primary murine leukemias to remain dependent on NOTCH1 signaling despite Pten loss, with or without additional deletion of p16(Ink4a)/p19(Arf). We also examined 13 primary human T-ALL samples obtained at diagnosis and found no correlation between PTEN status and resistance to Notch inhibition. Furthermore, we noted in the mouse model that Pten loss accelerated disease onset and produced multiclonal tumors, suggesting NOTCH1 activation and Pten loss may collaborate in leukemia induction. Thus, in contrast to previous findings with established cell lines, these results indicate PTEN loss does not relieve primary T-ALL cells of their "addiction" to Notch signaling.

Braf(V600E) cooperates with Pten loss to induce metastatic melanoma.

Mutational activation of BRAF is the earliest and most common genetic alteration in human melanoma. To build a model of human melanoma, we generated mice with conditional melanocyte-specific expression of BRaf(V600E). Upon induction of BRaf(V600E) expression, mice developed benign melanocytic hyperplasias that failed to progress to melanoma over 15-20 months. By contrast, expression of BRaf(V600E) combined with Pten tumor suppressor gene silencing elicited development of melanoma with 100% penetrance, short latency and with metastases observed in lymph nodes and lungs. Melanoma was prevented by inhibitors of mTorc1 (rapamycin) or MEK1/2 (PD325901) but, upon cessation of drug administration, mice developed melanoma, indicating the presence of long-lived melanoma-initiating cells in this system. Notably, combined treatment with rapamycin and PD325901 led to shrinkage of established melanomas. These mice, engineered with a common genetic profile to human melanoma, provide a system to study melanoma's cardinal feature of metastasis and for preclinical evaluation of agents designed to prevent or treat metastatic disease.

Pot1b deletion and telomerase haploinsufficiency in mice initiate an ATR-dependent DNA damage response and elicit phenotypes resembling dyskeratosis congenita.

The Protection of telomeres 1 (POT1) protein is a single-stranded telomere binding protein that is essential for proper maintenance of telomere length. Disruption of POT1 function leads to chromosome instability and loss of cellular viability. Here, we show that targeted deletion of the mouse Pot1b gene results in increased apoptosis in highly proliferative tissues. In the setting of telomerase haploinsufficiency, loss of Pot1b results in depletion of germ cells and complete bone marrow failure due to increased apoptosis, culminating in premature death. Pot1b(-/-) mTR(+/-) hematopoietic progenitor and stem cells display markedly reduced survival potential in vitro. Accelerated telomere shortening, increased G overhang and elevated number of chromosome end-to-end fusions that initiate an ATR-dependent DNA damage response were also observed. These results indicate an essential role for Pot1b in the maintenance of genome integrity and the long-term viability of proliferative tissues in the setting of telomerase deficiency. Interestingly, these phenotypes closely resemble those found in the human disease dyskeratosis congenita (DC), an inherited syndrome characterized by bone marrow failure, hyperpigmentation, and nail dystrophy. We anticipate that this mouse will serve as a useful model to further understand the pathophysiology of DC.

p53 and Pten control neural and glioma stem/progenitor cell renewal and differentiation.

Glioblastoma (GBM) is a highly lethal brain tumour presenting as one of two subtypes with distinct clinical histories and molecular profiles. The primary GBM subtype presents acutely as a high-grade disease that typically harbours mutations in EGFR, PTEN and INK4A/ARF (also known as CDKN2A), and the secondary GBM subtype evolves from the slow progression of a low-grade disease that classically possesses PDGF and TP53 events. Here we show that concomitant central nervous system (CNS)-specific deletion of p53 and Pten in the mouse CNS generates a penetrant acute-onset high-grade malignant glioma phenotype with notable clinical, pathological and molecular resemblance to primary GBM in humans. This genetic observation prompted TP53 and PTEN mutational analysis in human primary GBM, demonstrating unexpectedly frequent inactivating mutations of TP53 as well as the expected PTEN mutations. Integrated transcriptomic profiling, in silico promoter analysis and functional studies of murine neural stem cells (NSCs) established that dual, but not singular, inactivation of p53 and Pten promotes an undifferentiated state with high renewal potential and drives increased Myc protein levels and its associated signature. Functional studies validated increased Myc activity as a potent contributor to the impaired differentiation and enhanced renewal of NSCs doubly null for p53 and Pten (p53(-/-) Pten(-/-)) as well as tumour neurospheres (TNSs) derived from this model. Myc also serves to maintain robust tumorigenic potential of p53(-/-) Pten(-/-) TNSs. These murine modelling studies, together with confirmatory transcriptomic/promoter studies in human primary GBM, validate a pathogenetic role of a common tumour suppressor mutation profile in human primary GBM and establish Myc as an important target for cooperative actions of p53 and Pten in the regulation of normal and malignant stem/progenitor cell differentiation, self-renewal and tumorigenic potential.

Identification of a PTEN-regulated STAT3 brain tumor suppressor pathway.

Activation of the transcription factor STAT3 is thought to potently promote oncogenesis in a variety of tissues, leading to intense efforts to develop STAT3 inhibitors for many tumors, including the highly malignant brain tumor glioblastoma. However, the function of STAT3 in glioblastoma pathogenesis has remained unknown. Here, we report that STAT3 plays a pro-oncogenic or tumor-suppressive role depending on the mutational profile of the tumor. Deficiency of the tumor suppressor PTEN triggers a cascade that inhibits STAT3 signaling in murine astrocytes and human glioblastoma tumors. Specifically, we forge a direct link between the PTEN-Akt-FOXO axis and the leukemia inhibitory factor receptor beta (LIFRbeta)-STAT3 signaling pathway. Accordingly, PTEN knockdown induces efficient malignant transformation of astrocytes upon knockout of the STAT3 gene. Remarkably, in contrast to the tumor-suppressive function of STAT3 in the PTEN pathway, STAT3 forms a complex with the oncoprotein epidermal growth factor receptor type III variant (EGFRvIII) in the nucleus and thereby mediates EGFRvIII-induced glial transformation. These findings indicate that STAT3 plays opposing roles in glial transformation depending on the genetic background of the tumor, providing the rationale for tailored therapeutic intervention in glioblastoma.

The PTEN and INK4A/ARF tumor suppressors maintain myelolymphoid homeostasis and cooperate to constrain histiocytic sarcoma development in humans.

Histiocytic sarcoma (HS) is a rare malignant proliferation of histiocytes of uncertain molecular pathogenesis. Here, genetic analysis of coincident loss of Pten and Ink4a/Arf tumor suppressors in the mouse revealed a neoplastic phenotype dominated by a premalignant expansion of biphenotypic myelolymphoid cells followed by the development of HS. Pten protein loss occurred only in the histiocytic portion of tumors, suggesting a stepwise genetic inactivation in the generation of HS. Similarly, human HS showed genetic or epigenetic inactivation of PTEN, p16(INK4A), and p14(ARF), supporting the relevance of this genetically engineered mouse model of HS. These genetic and translational observations establish a cooperative role of Pten and Ink4a/Arf in the development of HS and provide mechanistic insights into the pathogenesis of human HS.

High-resolution genomic profiles of human lung cancer.

Lung cancer is the leading cause of cancer mortality worldwide, yet there exists a limited view of the genetic lesions driving this disease. In this study, an integrated high-resolution survey of regional amplifications and deletions, coupled with gene-expression profiling of non-small-cell lung cancer subtypes, adenocarcinoma and squamous-cell carcinoma (SCC), identified 93 focal copy-number alterations, of which 21 span <0.5 megabases and contain a median of five genes. Whereas all known lung cancer genes/loci are contained in the dataset, most of these recurrent copy-number alterations are previously uncharacterized and include high-amplitude amplifications and homozygous deletions. Notably, despite their distinct histopathological phenotypes, adenocarcinoma and SCC genomic profiles showed a nearly complete overlap, with only one clear SCC-specific amplicon. Among the few genes residing within this amplicon and showing consistent overexpression in SCC is p63, a known regulator of squamous-cell differentiation. Furthermore, intersection with the published pancreatic cancer comparative genomic hybridization dataset yielded, among others, two focal amplicons on 8p12 and 20q11 common to both cancer types. Integrated DNA-RNA analyses identified WHSC1L1 and TPX2 as two candidates likely targeted for amplification in both pancreatic ductal adenocarcinoma and non-small-cell lung cancer.

Epidermal growth factor receptor and Ink4a/Arf: convergent mechanisms governing terminal differentiation and transformation along the neural stem cell to astrocyte axis.

Ink4a/Arf inactivation and epidermal growth factor receptor (EGFR) activation are signature lesions in high-grade gliomas. How these mutations mediate the biological features of these tumors is poorly understood. Here, we demonstrate that combined loss of p16(INK4a) and p19(ARF), but not of p53, p16(INK4a), or p19(ARF), enables astrocyte dedifferentiation in response to EGFR activation. Moreover, transduction of Ink4a/Arf(-/-) neural stem cells (NSCs) or astrocytes with constitutively active EGFR induces a common high-grade glioma phenotype. These findings identify NSCs and astrocytes as equally permissive compartments for gliomagenesis and provide evidence that p16(INK4a) and p19(ARF) synergize to maintain terminal astrocyte differentiation. These data support the view that dysregulation of specific genetic pathways, rather than cell-of-origin, dictates the emergence and phenotype of high-grade gliomas.

Genetic analysis of Pten and Ink4a/Arf interactions in the suppression of tumorigenesis in mice.

Dual inactivation of PTEN and INK4a/ARF tumor suppressor genes is a common feature observed in a broad spectrum of human cancer types. To validate functional collaboration between these genes in tumor suppression, we examined the biological consequences of Pten and/or Ink4a/Arf deficiency in cells and mice. Relative to single mutant controls, Ink4a/Arf-/-Pten+/- mouse embryonic fibroblast cultures exhibited faster rates of growth in reduced serum, grew to higher saturation densities, produced more colonies upon low density seeding, and showed increased susceptibility to transformation by oncogenic H-Ras. Ink4a/Arf deficiency reduced tumor-free survival and shortened the latency of neoplasias associated with Pten heterozygosity, specifically pheochromocytoma, prostatic intraepithelial neoplasia, and endometrial hyperplasia. Compound mutant mice also exhibited an expanded spectrum of tumor types including melanoma and squamous cell carcinoma. Functional synergy between Ink4a/Arf and Pten manifested most prominently in the development of pheochromocytoma, prompting an analysis of genes and loci implicated in this rare human neoplasm. The classical pheochromocytoma genes Ret, Vhl, and Nf-1 remained intact, a finding consistent with the intersection of these genes with pathways engaged by Pten and Ink4a/Arf. Notably, conventional and array-comparative genomic hybridization revealed frequent loss of distal mouse chromosome 4 in a region syntenic to human chromosome 1p that is implicated in human pheochromocytoma. This study provides genetic evidence of collaboration between Pten and Ink4a/Arf in constraining the growth and oncogenic transformation of cultured cells and in suppressing a wide spectrum of tumors in vivo.