Abstract IA017: An oncogenic histone reader promotes metaplastic TNBC

Human carcinosarcomas or metaplastic breast cancers (MpBC) are a rare, chemorefractory subclass of triple-negative breast cancers (TNBC). Conditional overexpression of histone reader Tripartite motif containing protein 24 (TRIM24) in mouse mammary epithelia (Trim24COE) led to spontaneous development of mammary carcinosarcoma tumors, lacking ER, PR and HER2, comprising 70% of all mammary tumors that developed with 40% penetrance. We saw strong correlation of Trim24COE carcinosarcoma tumors with human MpBC tumors and derived a conserved Trim24COE gene signature of Glycolysis, EMT and mTORC1 signaling pathways. Global and single-cell tumor profiling revealed Met as a direct oncogenic target of TRIM24, leading to aberrant PI3K/mTOR activation. To assess TRIM24-dependent metabolic alterations, we developed Trim24COE carcinosarcoma spheroid cultures. Tumor-derived Trim24COE carcinosarcoma spheroids exhibit TRIM24-dependent EMT and repressed cellular and mitochondrial ROS levels. We found that TRIM24 expression increased c-myc, NADPH and NRF2 levels to drive ROS repression and TRIM24-dependent cell survival under oxidative stress. TRIM24 mediates NRF2 activation at the level of chromatin structure activation, as shown by ATAC-seq of Trim24COE and shTrim24 carcinosarcoma spheroids. These in vivo and ex vivo models of metaplastic TNBC offer a platform for mechanistic discovery and nomination of potential therapeutic avenues for this highly malignant TNBC subtype.

Citation Format: Vrutant V. Shah, Shucheng Miao, Patrick M. Krause, Sabrina A. Stratton, Lalit R. Patel, Michelle C. Barton. An oncogenic histone reader promotes metaplastic TNBC [abstract]. In: Proceedings of the AACR Special Conference: Aging and Cancer; 2022 Nov 17-20; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2022;83(2 Suppl_1):Abstract nr IA017.

Mammary-specific expression of Trim24 establishes a mouse model of human metaplastic breast cancer

Conditional overexpression of histone reader Tripartite motif containing protein 24 (TRIM24) in mouse mammary epithelia (Trim24COE) drives spontaneous development of mammary carcinosarcoma tumors, lacking ER, PR and HER2. Human carcinosarcomas or metaplastic breast cancers (MpBC) are a rare, chemorefractory subclass of triple-negative breast cancers (TNBC). Comparison of Trim24COE metaplastic carcinosarcoma morphology, TRIM24 protein levels and a derived Trim24COE gene signature reveals strong correlation with human MpBC tumors and MpBC patient-derived xenograft (PDX) models. Global and single-cell tumor profiling reveal Met as a direct oncogenic target of TRIM24, leading to aberrant PI3K/mTOR activation. Here, we find that pharmacological inhibition of these pathways in primary Trim24COE tumor cells and TRIM24-PROTAC treatment of MpBC TNBC PDX tumorspheres decreased cellular viability, suggesting potential in therapeutically targeting TRIM24 and its regulated pathways in TRIM24-expressing TNBC.

miR-199 plays both positive and negative regulatory roles in Xenopus eye development

To investigate microRNA (miR) functions in early eye development, we asked whether eye field transcription factors (EFTFs) are targets of miR-dependent regulation in Xenopus embryos. Argonaute (AGO) ribonucleoprotein complexes, including miRs and targeted mRNAs, were coimmunoprecipitated from transgenic embryos expressing myc-tagged AGO under the control of the rax1 promoter; mRNAs for all EFTFs coimmunoprecipitated with Ago in late neurulae. Computational predictions of miR binding sites within EFTF 3'UTRs identified miR-199a-3p ("miR-199") as a candidate regulator of EFTFs, and miR-199 was shown to regulate rax1 in vivo. Targeted overexpression of miR-199 led to small eyes, a reduction in EFTF expression, and reduced cell proliferation. Inhibition of interactions between mir-199 and the rax1 3'UTR reversed the small eye phenotype. Although targeted knockdown of miR-199 left the eye field intact, it reduced optic cup outgrowth and disrupted eye formation. Computational identification of candidate miR-199 targets within the Xenopus transcriptome led to the identification of ptk7 as a candidate regulator. Targeted overexpression of ptk7 resulted in abnormal optic cup formation and a reduction or loss of eye development, recapitulating the range of eye phenotypes seen following miR-199 knockdown. Our results indicate that miR-199 plays both positive and negative regulatory roles in eye development.

Abstract 4626: A TRIM24-like mutational signature predicts worse relapse-free survival (RFS) and overall survival (OS) in patients (pts) with metaplastic breast cancer (MpBC)

Background: TRIM24 is a multifunctional, epigenetic PHD/Bromodomain protein that negatively regulates p53, via an E3-ubiquitin ligase RING domain, and co-regulates transcription. Over-expression of TRIM24 in murine mammary epithelium results in the development of carcinosarcomas that bear close histologic resemblance to human MpBCs and are characterized by a distinct genomic signature. Here, we investigate the association between the presence of a TRIM24-like mutational signature and clinical outcomes in a cohort of human MpBCs.

Methods: 20 archived samples of human MpBC with annotated clinical data underwent whole exome sequencing. In parallel, we sequenced 7 spontaneously arising carcinosarcomas from a TRIM24 overexpressing mouse model. To compare the mutations with those seen in the human MpBCs, we grouped them into pathways and created a signature of pathway activation seen in TRIM24-driven tumors. Median RFS and OS were estimated using the Kaplan-Meier method and compared between pts with and without a TRIM24-like mutational signature.

Results: Baseline clinical characteristics are summarized in Table 1. Of the 20 MpBC pts, 5 had a TRIM24-like mutational signature and the remaining 15 pts did not. There were no statistically significant differences in baseline characteristics between the 2 groups. Median RFS for pts with a TRIM24-like mutational signature was 9 months (95% confidence interval [CI]: 8-undefined months). Median RFS for pts without a TRIM24-like mutational signature has not been reached (log-rank, p=0.0149). Median OS for pts with and without a TRIM24-like mutational signature was 17 months (95% CI: 10-undefined months) and 147 months (95% CI: 22-undefined months), respectively (log-rank, p=0.0402).

Conclusion: In this cohort, pts with MpBCs that exhibit a TRIM24-like mutational signature had worse RFS and OS. This finding should be confirmed in larger, prospective studies.

Table 1: Baseline Clinicopathological Characteristics by TRIM24 StatusTRIM24-like (n=5)Non TRIM24-like (n=15)p valueAge at diagnosis - Median (years, interquartile range)55 (50-61)56 (47-66)0.965Clinical Tumor SizeMean (cm, standard deviation)4.2 (1.5)3.4 (1.6)0.383Clinical Nodal StatusNegative - n (%)3 (60)11 (73)0.570Positive - n (%)2 (40)3 (20)Unknown - n (%)01 (7)ER/PR StatusNegative - n (%)5 (100)14 (93)1.000Positive - n (%)01 (7)HER2 StatusNegative - n (%)5 (100)15 (100)NAPositive - n (%)00HistologySpindle Cell - n (%)4 (80)7 (47)0.319Matrix-producing - n (%)1 (20)8 (53)

Citation Format: Clinton Yam, Aundrietta Duncan, Jeffrey T. Chang, Michael Z. Gilcrease, Vrutant V. Shah, Michelle Barton, Stacy L. Moulder. A TRIM24-like mutational signature predicts worse relapse-free survival (RFS) and overall survival (OS) in patients (pts) with metaplastic breast cancer (MpBC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4626.

Scalp hypothermia as a preventative measure for chemotherapy-induced alopecia: a review of controlled clinical trials

Chemotherapy-induced alopecia (CIA) is a temporary, yet psychologically devastating form of hair loss that affects 65% of patients receiving cancer chemotherapy. In the 1970s, scalp hypothermia was introduced as a preventative measure against the development of CIA. Numerous studies provide evidence for the effectiveness of scalp cooling to prevent CIA, although results varied because of differences in chemotherapy regimen, cooling technique, mode of administration and patient factors. However, many of the existing studies are uncontrolled or consist of small sample sizes, and data from randomized, randomized studies are limited. To date, no clear guidelines have been established for optimum scalp cooling use as a treatment modality and its efficacy remain unknown. Nonetheless, scalp cooling remains the most widely utilized method for the prevention of CIA, and in December 2015, the United States Food and Drug Administration (FDA) cleared the DigniCap^® Scalp Cooling System (Dignitana AB, Sweden) for marketing and the Orbis from Paxman^® Coolers Ltd. received clearance in 2017. This literature review is one of the first to provide up-to-date review and side-by-side comparisons of controlled and randomized clinical trials (CCTs and RCTs) evaluating scalp hypothermia for the prevention of CIA. Our analyses of CCTs and RCTs to date show that scalp hypothermia is effective in reducing the occurrence rate of CIA, by 2.7-fold in the CCTs and 3.9-fold in the RCTs. These results suggest that scalp hypothermia represents an effective preventative measure for CIA, and provide guidance for management of anticipated alopecia following chemotherapy and for future investigations.

Data on microRNAs and microRNA-targeted mRNAs in Xenopus ectoderm

Small RNAs from early neural (i.e., Noggin-expressing, or NOG) and epidermal (expressing a constitutively active BMP4 receptor, CABR) ectoderm in Xenopus laevis were sequenced to identify microRNAs (miRs) expressed in each tissue. Argonaute-associated mRNAs were isolated and sequenced to identify genes that are regulated by microRNAs in these tissues. Interactions between these ectodermal miRs and selected miR-regulated mRNAs were predicted using the PITA algorithm; PITA predictions for over 600 mRNAs are presented. All sequencing data are available at NCBI (NCBI Bioproject Accession number: PRJNA325834). This article accompanies the manuscript “MicroRNAs and ectodermal specification I. Identification of miRs and miR-targeted mRNAs in early anterior neural and epidermal ectoderm” (V.V. Shah, B. Soibam, R.A. Ritter, A. Benham, J. Oomen, A.K. Sater, 2016) [1].

MicroRNAs and ectodermal specification I. Identification of miRs and miR-targeted mRNAs in early anterior neural and epidermal ectoderm

The establishment of cell lineages occurs via a dynamic progression of gene regulatory networks (GRNs) that underlie developmental commitment and differentiation. To investigate how microRNAs (miRs) function in this process, we compared miRs and miR targets at the initiation of the two major ectodermal lineages in Xenopus. We used next-generation sequencing to identify over 170 miRs expressed in midgastrula ectoderm expressing either noggin or a constitutively active BMP receptor, reflecting anterior neural or epidermal ectoderm, respectively; 125 had not previously been identified in Xenopus. We identified the locations of the pre-miR sequences in the X. laevis genome. Neural and epidermal ectoderm express broadly similar sets of miRs. To identify targets of miR-dependent translational control, we co-immunoprecipitated Argonaute-Ribonucleoprotein (Ago-RNP) complexes from early neural and epidermal ectoderm and sequenced the associated RNA. The Ago-RNP RNAs from these tissues represent overlapping, yet distinct, subsets of genes. Moreover, the profile of Ago-RNP associated genes differs substantially from the profile of total RNAs in these tissues. We generated target predictions for the "high confidence" Ago-RNP RNAs using the identified ectodermal miRs; These RNAs generally had target sites for multiple miRs. Oct4 orthologues, as well as many of their previously identified transcriptional targets, are represented in the Ago-RNP pool in both tissues, suggesting that miR-dependent regulation contributes to the downregulation of the oct4 gene regulatory network and the reduction in ectodermal pluripotency.

Measuring Newtonian viscosity from the phase of reflected ultrasonic shear wave

In this paper, an acoustic shear impedance model is employed to obtain a relation between the viscosity of a Newtonian fluid and phase characteristics of ultrasonic shear wave reflection from a solid-fluid interface. The phase and magnitude of the reflection coefficient can be decoupled in this model. The decoupling allows an independent relation between the acoustic shear impedance (viscosity-density product) and phase of the reflection coefficient. The model was experimentally verified for different fluid-solid combinations. Comparison of the results with the commonly used absolute reflection coefficient method demonstrates that phase measurement provides improved measurements.

Design of an achromatic beam splitter comprising a dielectric multilayer stack

The inverse transmittance (1/T) of a quarterwave all dielectric multilayer stack is expressed as a mixed series in sinø and cosø, where ø = (pi/2)[(lambda - lambda(0))/ lambda] and lambda(0) is the reference wavelength. This expression has been used to design achromatic beam splitters for the visible and near IR regions having different reflectance (R) to transmittance (T) ratios (e.g. R:T = 70:30, 30:70, 50:50, 60:40, 40:60, etc.). The theoretical design places emphasis on the selection of refractive indices which can be realized in practice.

General expression for the reflectance of an all-dielectric multilayer stack

A converted characteristic matrix method has been used to derive a generalized expression for reflectance R (for wavelength lambda at normal incidence) of an all-dielectric multilayer stack consisting of K layers of refractive indices n(1),n(2),n(3)... n(k-1),n(k) having quarterwave thicknesses at the monitoring wavelength lambda(0). The expression thus derived is of the form R = Sigma(K)(N=0)(P(N) tan(2N)?)/(Q(N)tan(2N)?), where P(N) and Q(N) are functions of refractive indices and their interdependence is expressed by the relation (Q(N) - P(N))/(4n(S)) = (K!)/N!(K - N)!]. This expression shows that R is a function of (i) the refractive indices of the various layers in the multilayer structure and (ii) the parameter ? = {(Pi/2) [(lambda - lambda(0))/lambda]} which assumes positive or negative values depending on whether lambda < lambda(0) or A > lambda(0) such that within limits of acceptable variations (Deltalambda) in lambda(0), R remains unaffected at +/-?. An outcome of this analysis is that it can be used in identifying, to a limited extent, the structure of an unknown optical coating once the experimentally observed parameters R and T are known.

Periodic dielectric multifilm stack with symmetrical period having films of three different refractive indices: use as a heat reflecting mirror

Results of the theoretical computations of reflectance and transmittance values of periodic dielectric multifilm stacks with symmetrical periods, each consisting of films of three different refractive indices, are reported. The analysis yields good estimates of the bandwidths of the low reflectance and high reflectance zones for different compositions of the periodic structures, and one of the structures offers the possibility of use as a heat reflecting mirror. This particular structure when combined with a previously published design gives a heat reflecting mirror design with good spectral characteristics and seems to be relatively easy to fabricate, while the earlier design, which exhibits somewhat superior spectral characteristics, appears to be extremely difficult to fabricate.

High-carbohydrate diet and atherosclerosis in rabbits

In a study of physical and nutritional characteristics of cases of coronary heart disease, it was found that a large number of patients had low intake of fat, about 50 gm per day, and their carbohydrate intake was high. As a result high-carbohydrate diet was considered to be a possible factor in atherosclerosis. Yudkin also incriminated sugars in the causation of coronary atherosclerosis. Therefore a study was planned to assess the effect of high-carbohydrate diet on coronary arteries of rabbits. In this experiment it was decided to study the effect of high-carbohydrate diet alone on lipid fractions in the blood and the effects on coronary arteries and aorta when added fats are not given.