Differential histone acetylation and super-enhancer regulation underlie melanoma cell dedifferentiation

Dedifferentiation or phenotype switching refers to the transition from a proliferative to an invasive cellular state. We previously identified a 122-gene epigenetic gene signature that classifies primary melanomas as low versus high risk (denoted as Epgn1 or Epgn3). We found that the transcriptomes of the Epgn1 low-risk and Epgn3 high-risk cells are similar to the proliferative and invasive cellular states, respectively. These signatures were further validated in melanoma tumor samples. Examination of the chromatin landscape revealed differential H3K27 acetylation in the Epgn1 low-risk versus Epgn3 high-risk cell lines that corroborated with a differential super-enhancer and enhancer landscape. Melanocytic lineage genes (MITF, its targets and regulators) were associated with super-enhancers in the Epgn1 low-risk state, whereas invasiveness genes were linked with Epgn3 high-risk status. We identified the ITGA3 gene as marked by a super-enhancer element in the Epgn3 invasive cells. Silencing of ITGA3 enhanced invasiveness in both in vitro and in vivo systems, suggesting it as a negative regulator of invasion. In conclusion, we define chromatin landscape changes associated with Epgn1/Epgn3 and phenotype switching during early steps of melanoma progression that regulate transcriptional reprogramming. This super-enhancer and enhancer-driven epigenetic regulatory mechanism resulting in major changes in the transcriptome could be important in future therapeutic targeting efforts.

Altered BAF occupancy and transcription factor dynamics in PBAF-deficient melanoma

ARID2 is the most recurrently mutated SWI/SNF complex member in melanoma; however, its tumor-suppressive mechanisms in the context of the chromatin landscape remain to be elucidated. Here, we model ARID2 deficiency in melanoma cells, which results in defective PBAF complex assembly with a concomitant genomic redistribution of the BAF complex. Upon ARID2 depletion, a subset of PBAF and shared BAF-PBAF-occupied regions displays diminished chromatin accessibility and associated gene expression, while BAF-occupied enhancers gain chromatin accessibility and expression of genes linked to the process of invasion. As a function of altered accessibility, the genomic occupancy of melanoma-relevant transcription factors is affected and significantly correlates with the observed transcriptional changes. We further demonstrate that ARID2-deficient cells acquire the ability to colonize distal organs in multiple animal models. Taken together, our results reveal a role for ARID2 in mediating BAF and PBAF subcomplex chromatin dynamics with consequences for melanoma metastasis.

NOTCH and EZH2 collaborate to repress PTEN expression in breast cancer

Downregulation of the PTEN tumor suppressor transcript is frequent in breast cancer and associates with poor prognosis and triple-negative breast cancer (TNBC) when comparing breast cancers to one another. Here we show that in almost all cases, when comparing breast tumors to adjacent normal ducts, PTEN expression is decreased and the PRC2-associated methyltransferase EZH2 is increased. We further find that when comparing breast cancer cases in large cohorts, EZH2 inversely correlates with PTEN expression. Within the highest EZH2 expressing group, NOTCH alterations are frequent, and also associate with decreased PTEN expression. We show that repression of PTEN occurs through the combined action of NOTCH (NOTCH1 or NOTCH2) and EZH2 alterations in a subset of breast cancers. In fact, in cases harboring NOTCH1 mutation or a NOTCH2 fusion gene, NOTCH drives EZH2, HES-1, and HEY-1 expression to repress PTEN transcription at the promoter, which may contribute to poor prognosis in this subgroup. Restoration of PTEN expression can be achieved with an EZH2 inhibitor (UNC1999), a γ-secretase inhibitor (Compound E), or knockdown of EZH2 or NOTCH. These findings elucidate a mechanism of transcriptional repression of PTEN induced by NOTCH1 or NOTCH2 alterations, and identifies actionable signaling pathways responsible for driving a large subset of poor-prognosis breast cancers.

Pappas et al. show that the combination of NOTCH and EZH2 alterations drive transcriptional repression of PTEN through reversible epigenetic modification of the PTEN promoter. These results suggest an actionable target for treating poor-prognosis breast cancer.

Active case-finding in contacts of people with TB

BACKGROUND: Exposure to people with TB substantially elevates a person's risk of tuberculous infection and TB disease. Systematic screening of TB contacts enables the early detection and treatment of co-prevalent disease, and the opportunity to prevent future TB disease. However, scale-up of contact investigation in high TB transmission settings remains limited.METHODS: We undertook a narrative review to evaluate the evidence for contact investigation and identify strategies that TB programmes may consider when introducing contact investigation and management.RESULTS: Selection of contacts for priority screening depends upon their proximity and duration of exposure, along with their susceptibility to develop TB. Screening algorithms can be tailored to the target population, the availability of diagnostic tests and preventive therapy, and healthcare worker expertise. Contact investigation may be performed in the household or at communal locations. Local contact investigation policies should support vulnerable patients, and ensure that drop-out during screening can be mitigated. Ethical issues should be anticipated and addressed in each setting.CONCLUSION: Contact investigation is an important strategy for TB elimination. While its epidemiological impact will be greatest in lower-transmission settings, the early detection and prevention of TB have important benefits for contacts and their communities.

Palbociclib (PD-0332991), a selective CDK4/6 inhibitor, restricts tumour growth in preclinical models of hepatocellular carcinoma

OBJECTIVE

Advanced hepatocellular carcinoma (HCC) is a lethal malignancy with limited treatment options. Palbociclib, a well-tolerated and selective CDK4/6 inhibitor, has shown promising results in the treatment of retinoblastoma (RB1)-positive breast cancer. RB1 is rarely mutated in HCC, suggesting that palbociclib could potentially be used for HCC therapy. Here, we provide a comprehensive characterisation of the efficacy of palbociclib in multiple preclinical models of HCC.

DESIGN

The effects of palbociclib on cell proliferation, cellular senescence and cell death were investigated in a panel of human liver cancer cell lines, in ex vivo human HCC samples, in a genetically engineered mouse model of liver cancer, and in human HCC xenografts in vivo. The mechanisms of intrinsic and acquired resistance to palbociclib were assessed in human liver cancer cell lines and human HCC samples by protein and gene expression analyses.

RESULTS

Palbociclib suppressed cell proliferation in human liver cancer cell lines by promoting a reversible cell cycle arrest. Intrinsic and acquired resistance to palbociclib was determined by loss of RB1. A signature of 'RB1 loss of function' was found in <30% of HCC samples. Palbociclib, alone or combined with sorafenib, the standard of care for HCC, impaired tumour growth in vivo and significantly increased survival.

CONCLUSIONS

Palbociclib shows encouraging results in preclinical models of HCC and represents a novel therapeutic strategy for HCC treatment, alone or particularly in combination with sorafenib. Palbociclib could potentially benefit patients with RB1-proficient tumours, which account for 70% of all patients with HCC.

Recurrent point mutations in the kinetochore gene KNSTRN in cutaneous squamous cell carcinoma

Here we report the discovery of recurrent mutations concentrated at an ultraviolet signature hotspot in KNSTRN, which encodes a kinetochore protein, in 19% of cutaneous squamous cell carcinomas (SCCs). Cancer-associated KNSTRN mutations, most notably those encoding p.Ser24Phe, disrupt chromatid cohesion in normal cells, occur in SCC precursors, correlate with increased aneuploidy in primary tumors and enhance tumorigenesis in vivo. These findings suggest a role for KNSTRN mutagenesis in SCC development.

Stability and interactions of recombinant human nerve growth factor in different biological matrices: in vitro and in vivo studies

The purpose of this investigation was to characterize the stability, activity, and interactions of recombinant human nerve growth factor (rhNGF) in various biological matrices in vitro and in vivo. rhNGF (10 microg/ml) remained stable in human plasma for up to 4 days at 37 degrees C. There was a decrease in the recovery of rhNGF after incubation at lower concentrations (20 ng/ml) and for longer time periods (3 and 5 days at 37 degrees C). Size exclusion HPLC analysis indicated that rhNGF forms high molecular weight (HMW) complexes after long incubation periods. We confirmed that alpha(2)-macroglobulin (alpha(2)M) is the major plasma component that binds to rhNGF. Furthermore, this interaction was considerably increased by treatment of plasma with primary amines such as CH(3)NH(2). Changes in the pH environment did not affect the interaction of rhNGF with alpha(2)M. We also determined that the binding of rhNGF to CH(3)NH(2)-treated pure alpha(2)M or alpha(2)M present in human plasma substantially diminished its immunoreactivity and bioactivity detection. The interaction of rhNGF with activated alpha(2)M was reversed and inhibited by coincubation with dimethyl sulfoxide. Released rhNGF under these conditions was fully bioactive. (125)I-rhNGF also binds to alpha(2)M by forming similar (125)I-rhNGF/HMW complexes in plasma after i.v. administration in rats and mice. Sixty minutes after dosing in rats, most of the labeled material was in the form of a (125)I-rhNGF/HMW complex. These studies have provided a better understanding of the nature of the interactions of rhNGF with plasma components as well as methods to enhance, reverse, and inhibit these interactions.

Tissue disposition and pharmacokinetics of recombinant human nerve growth factor after acute and chronic subcutaneous administration in monkeys

In this study, we have characterized the metabolism, tissue disposition, excretion routes, and plasma pharmacokinetics of recombinant human nerve growth factor after single and multiple s.c. administration in male cynomolgus monkeys. Unlabeled nerve growth factor (NGF; 2 mg/kg) was administered three times a week for 4 weeks and a full pharmacokinetic profile was obtained for doses 1 and 12. For the tissue distribution studies, 0.8 microg/kg of trace (125)I-labeled recombinant human nerve growth factor was dosed. Histological analysis of emulsion-microautoradiography indicated that specific (125)I-NGF labeling was confined to sections of nerves most frequently localized adjacent to large vessels in sections of kidney, spleen, liver, and salivary gland. A small percentage of large neurons within the sympathetic ganglia were intensely labeled, as well as large neurons within the dorsal root ganglia. We found an increased disposition of (125)I-NGF in parts of the peripheral nervous system (including sympathetic ganglia) from 8 to 24 h postdose. In contrast, radioactivity in most non-neuronal tissues declined. This suggests specific uptake in these target tissues known to express specific receptors for NGF. We also identified changes in pharmacokinetic parameters after single versus chronic s. c. administration. These studies demonstrated that s.c. administration of NGF at 0.8 microg/kg doses in monkeys is capable of accessing and localizing in the target tissues.

Symptoms associated with oophorectomy and tamoxifen treatment for breast cancer in premenopausal Vietnamese women

There are very few data about the efficacy and toxicity of adjuvant systemic therapies for breast cancer in non-western populations. In 1993 in Vietnam we began a randomized controlled clinical trial on premenopausal women with operable breast cancer comparing adjuvant surgical oophorectomy plus tamoxifen with observation and this same combined hormonal treatment on recurrence. We evaluated the symptoms reported at regular follow-up visits by the first 482 premenopausal women entered in this clinical trial and treated with surgical oophorectomy plus tamoxifen or observation. Hot flash frequency and intensity, vaginal discharge, and genital pruritus were the only symptoms to occur more frequently in oophorectomy and tamoxifen-treated subjects. Seventy-seven percent of oophorectomy/tamoxifen subjects reported grade 1 or more and 44% grade 2 or more hot flash frequency symptoms in the first 12 months, versus 9% and 1% of observation subjects, respectively. Twenty percent of oophorectomy/tamoxifen subjects had grade 2 or greater intensity of hot flashes some time in the first 12 months versus 0% in observation subjects. Through three years, vasomotor symptoms were reported more frequently in oophorectomy/tamoxifen-treated women (in 23% vs. 3% at three years, mostly grade 1 toxicities). While noted and persistent vasomotor symptoms were found with oophorectomy plus tamoxifen in this population of Vietnamese women, these were of lower grades and tolerable. This adjuvant treatment may be widely accepted if it is demonstrated to be effective in this population.