How to use magnetic resonance imaging following neoadjuvant chemotherapy in locally advanced breast cancer

Magnetic resonance imaging (MRI) is highly sensitive in identifying residual breast cancer following neoadjuvant chemotherapy (NAC), and consequently is a commonly used imaging modality in locally advanced breast cancer patients. In these patients, tumor response is an important prognostic indicator. However, discrepancies between MRI findings and surgical pathology are well documented. Overestimation of residual disease by MRI may result in greater surgery than is actually required while underestimation may result in insufficient surgery. Thus, it is important to understand when MRI findings are reliable and when they are less accurate. MRI most accurately predicts pathology in triple negative, Her2 positive and hormone receptor negative tumors, especially if they are of a solid imaging phenotype. In these cases, post-NAC MRI is highly reliable for surgical planning. Hormone receptor positive cancers and those demonstrating non mass enhancement show lower concordance with surgical pathology, making surgical guidance more nebulous in these cases. Radiologists and surgeons must assess MRI response to NAC in the context of tumor subtype. Indiscriminate interpretations will prevent MRI from achieving its maximum potential in the pre-operative setting.

Abstract P3-01-04: Mammographic changes after oncoplastic reduction mammoplasty

BACKGROUND:

Reconstruction of partial lumpectomy defects with reduction mammaplasty techniques can improve aesthetic outcomes. However, the impact of the significant tissue rearrangement on post-operative mammographic findings and subsequent recommendations for biopsy has not been well-studied.

METHODS:

A retrospective review of 50 patients who underwent partial mastectomy with immediate oncoplastic reduction mammaplasty reconstruction from 2001 to 2008 was performed. Mammography reports at 6 months, 1 year, 2 years, and 3 years post-operatively were reviewed for Breast Imaging Reporting and Data System (BI-RADS) scores, predominant findings, and recommendations for subsequent imaging or biopsy.

RESULTS:

At six months post-operatively, 49 patients (98%) had benign findings of post-surgical changes, while one patient had microcalcifications and underwent subsequent surgical re-excision with residual DCIS on pathologic analysis. At one year, 94% of patients continued to have benign mammograms; of these mammograms, 94% reported only post-surgical scarring, while 6% described benign-appearing scattered or dystrophic calcifications. Of the three patients with suspicious mammograms at one year, all underwent core biopsies with benign results. At two years, rates of fat necrosis (2%) and scattered or dystrophic calcifications (10%) increased, though all mammographic findings were considered benign and none required additional imaging or biopsies. By three years post-operatively, an additional two patients (4%) developed suspicious findings and underwent biopsies confirming local recurrence (one invasive, one in situ). The remaining 96% continued to have benign mammographic findings and were subsequently followed with routine biannual mammographic surveillance.

Overall, 88% of patients required no additional intervention in the three-year period following oncoplastic reduction mammaplasty. Of patients recommended for biopsy, malignancy was discovered in 50%, including two local recurrences (4% of total patients). This data is similar to a previously published large study (1841 women) of mammographic surveillance after partial mastectomy without oncoplastic reconstruction at our institution, which found a 6% malignancy rate at 5 years.

CONCLUSIONS:

Although substantial tissue rearrangement is performed at the time of oncoplastic reduction mammaplasty, our results demonstrate low rates of abnormal post-operative mammograms and subsequent biopsies over the first three years following the procedure. These findings support the use of oncoplastic reduction mammaplasty as a strategy for improving reconstructive outcomes in patients undergoing partial mastectomy.

Citation Format: Anne Warren Peled, Merisa Piper, Laura J Esserman, Robert D Foster, Hani Sbitany, Elissa R Price. Mammographic changes after oncoplastic reduction mammoplasty [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P3-01-04.

Extra-mammary findings on breast MRI: a pictorial review

Recent improvements in breast coil performance have made detection of extra-mammary findings increasingly common. Some of these findings have important clinical implications. The radiologist should be aware of the spectrum of extra-mammary pathologies found on breast magnetic resonance imaging (MRI) and be able to distinguish clinically significant findings from those that are inconsequential. The purpose of this essay is to demonstrate various common and uncommon extra-mammary findings encountered while interpreting breast MRI and to detail appropriate management recommendations.

The California breast density information group: a collaborative response to the issues of breast density, breast cancer risk, and breast density notification legislation

In anticipation of breast density notification legislation in the state of California, which would require notification of women with heterogeneously and extremely dense breast tissue, a working group of breast imagers and breast cancer risk specialists was formed to provide a common response framework. The California Breast Density Information Group identified key elements and implications of the law, researching scientific evidence needed to develop a robust response. In particular, issues of risk associated with dense breast tissue, masking of cancers by dense tissue on mammograms, and the efficacy, benefits, and harms of supplementary screening tests were studied and consensus reached. National guidelines and peer-reviewed published literature were used to recommend that women with dense breast tissue at screening mammography follow supplemental screening guidelines based on breast cancer risk assessment. The goal of developing educational materials for referring clinicians and patients was reached with the construction of an easily accessible Web site that contains information about breast density, breast cancer risk assessment, and supplementary imaging. This multi-institutional, multidisciplinary approach may be useful for organizations to frame responses as similar legislation is passed across the United States. Online supplemental material is available for this article.

c-Kit triggers dual phosphorylations, which couple activation and degradation of the essential melanocyte factor Mi

Microphthalmia (Mi) is a bHLHZip transcription factor that is essential for melanocyte development and postnatal function. It is thought to regulate both differentiated features of melanocytes such as pigmentation as well as proliferation/survival, based on phenotypes of mutant mouse alleles. Mi activity is controlled by at least two signaling pathways. Melanocyte-stimulating hormone (MSH) promotes transcription of the Mi gene through cAMP elevation, resulting in sustained Mi up-regulation over many hours. c-Kit signaling up-regulates Mi function through MAP kinase phosphorylation of Mi, thereby recruiting the p300 transcriptional coactivator. The current study reveals that c-Kit signaling triggers two phosphorylation events on Mi, which up-regulate transactivation potential yet simultaneously target Mi for ubiquitin-dependent proteolysis. The specific activation/degradation signals derive from MAPK/ERK targeting of serine 73, whereas serine 409 serves as a substrate for p90 Rsk-1. An unphosphorylatable double mutant at these two residues is at once profoundly stable and transcriptionally inert. These c-Kit-induced phosphorylations couple transactivation to proteasome-mediated degradation. c-Kit signaling thus triggers short-lived Mi activation and net Mi degradation, in contrast to the profoundly increased Mi expression after MSH signaling, potentially explaining the functional diversity of this transcription factor in regulating proliferation, survival, and differentiation in melanocytes.

Isolation of mouse stromal cells associated with a human tumor using differential diphtheria toxin sensitivity

Tumor vascularization is accompanied by the migration of stromal cells, including endothelial cells, smooth muscle cells, and fibroblasts, into the tumor. The biological contributions of stromal cells to tumor vascularization have not been well-defined, partly due to the difficulty of culturing stromal cells in the presence of large numbers of fast-growing tumor cells. To address this problem, a strategy was devised to kill tumor cells but not stromal cells. Advantage was taken of the observation that diphtheria toxin (DT) kills human but not rodent cells. Human melanoma (MMAN) tumor cells were injected subcutaneously into nude mice. The tumors were excised, homogenized, and treated with 50 ng/ml DT for 24 hours. Elimination of melanoma cells by DT treatment was demonstrated by lack of detectable levels of microphthalmia, a transcription factor that is a marker for melanoma cells. The murine stromal cells were viable and found to be mostly smooth muscle cells. These cells constituted about 1.5% of the MMAN tumor. RNase protection assays using a specific murine vascular endothelial growth factor probe confirmed the murine origin of the stromal cells. This method allows rapid isolation of stromal cells and should facilitate biochemical and genetic analysis of tumor-stromal interactions.

alpha-Melanocyte-stimulating hormone signaling regulates expression of microphthalmia, a gene deficient in Waardenburg syndrome

The pituitary peptide alpha-melanocyte-stimulating hormone (alpha-MSH) stimulates melanocytes to up-regulate cAMP, but the downstream targets of cAMP are not well understood mechanistically. One consequence of alpha-MSH stimulation is increased melanization attributable to induction of pigmentation enzymes, including tyrosinase, which catalyzes a rate-limiting step in melanin synthesis. The tyrosinase promoter is a principle target of the melanocyte transcription factor Microphthalmia (Mi), a factor for which deficiency in humans causes Waardenburg syndrome II. We show here that both alpha-MSH and forskolin, a drug that increases cAMP, stimulate a rapid increase in Mi mRNA and protein levels in both melanoma cell lines and primary melanocytes. This up-regulation requires a cAMP-responsive element within the Mi promoter, and the pathway leading to Mi stimulation is subject to tight homeostatic regulation. Although cAMP signaling is ubiquitous, the Mi promoter was seen to be cAMP-responsive in melanocytes but not in nonmelanocytes. Moreover, dominant negative interference with Mi impeded successful alpha-MSH stimulation of tyrosinase. The regulation of Mi expression via alpha-MSH thus provides a direct mechanistic link to pigmentation. In addition, because the human melanocyte and deafness condition Waardenburg syndrome is sometimes caused by haploinsufficiency of Mi, its modulation by alpha-MSH suggests therapeutic strategies targeted at up-regulating the remaining wild type Mi allele.

Lineage-specific signaling in melanocytes. C-kit stimulation recruits p300/CBP to microphthalmia

During melanocyte development, the cytokine Steel factor activates its receptor c-Kit, initiating a signal transduction cascade, which is vital for lineage determination via unknown downstream nuclear targets. c-Kit has recently been found to trigger mitogen-activated protein kinase-mediated phosphorylation of Microphthalmia (Mi), a lineage-restricted transcription factor, which, like Steel factor and c-Kit, is essential for melanocyte development. This cascade results in increased Mi-dependent transcriptional reporter activity. Here we examine the mechanism by which Mi is activated by this pathway. Phosphorylation does not significantly alter Mi's nuclear localization, DNA binding, or dimerization. However, the transcriptional coactivator p300/CBP selectively associates with mitogen-activated protein kinase-phosphorylated Mi, even under conditions in which non-MAPK phospho-Mi is more abundant. Moreover, p300/CBP coactivates Mi transcriptional activity in a manner dependent upon this phosphorylation. Mi thus joins CREB as a transcription factor whose signal-responsive phosphorylation regulates coactivator recruitment, in this case modulating lineage development in melanocytes.

MAP kinase links the transcription factor Microphthalmia to c-Kit signalling in melanocytes

Germline mutations at loci encoding the transcription factor Microphthalmia (Mi), the cytokine receptor c-Kit, or its ligand Steel factor (S1) result in strikingly similar defects in mast cell and melanocyte development. Here we describe a biochemical link between Kit signalling and the activity of Mi. Stimulation of melanoma cells with S1 results in activation of MAP kinase, which in turn phosphorylates Mi at a consensus target serine. This phosphorylation upregulates Mi transactivation of the tyrosinase pigmentation gene promoter. In addition to modulating pigment production, such signalling may regulate the expression of genes essential for melanocyte survival and development. The pathway represents a new application of the general MAP kinase machinery in transducing a signal between a tissue-specific receptor at the cell surface and a tissue-specific transcription factor in the nucleus.

Role of kinases and the phosphatase calcineurin in the nuclear shuttling of transcription factor NF-AT4

A new facet of calcium signalling involves the nuclear import of the NF-AT transcription factors from their dormant position in the cytoplasm. The protein phosphatase calcineurin appears to play an essential role in activating NF-AT nuclear import, as the calcineurin inhibitors cyclosporin A and FK506 block dephosphorylation and nuclear import of NF-AT (refs 4-7). Here we show that calcium signalling induces an association between NF-AT4 and calcineurin, and that these molecules are transported, as a complex, to the nucleus, where calcineurin continues to dephosphorylate NF-AT4. We propose that a nuclear complex of NF-AT4 and calcineurin maintains calcium signalling by counteracting a vigorous nuclear NF-AT kinase.

The latch region of calcineurin B is involved in both immunosuppressant-immunophilin complex docking and phosphatase activation

The immunosuppressants cyclosporin A and FK506, when complexed with their intracellular receptors, prevent T cell activation by directly binding to the phosphatase calcineurin. We have used molecular modeling and mutagenesis to identify sites on calcineurin important for this interaction. We have created calcineurins that are resistant to both cyclosporin A and FK506 by mutating specific residues in CnB, a calcium-binding protein that regulates the catalytic subunit, CnA. Significantly, on a model of CnB, these mutations map to the latch region, an element of tertiary structure that forms when CnB binds CnA. In addition, we show that this latch region plays an important role in activating the catalytic subunit CnA. These results suggest a molecular mechanism for suppression of calcineurin by cyclosporin A and FK506 involving their binding to the same region of CnB used for allosterically activating CnA.

Cyclophilin B trafficking through the secretory pathway is altered by binding of cyclosporin A

Cyclophilin B is targeted to the secretory pathway via an endoplasmic reticulum signal sequence. We analyzed the localization and trafficking of endogenous and transfected cyclophilin B in mammalian cells. Cyclophilin B accumulates both in the endoplasmic reticulum and in complexes on the plasma membrane. The immunosuppressant cyclosporin A specifically mobilizes cyclophilin B from the endoplasmic reticulum, and promotes the secretion of cyclophilin B into the medium. We suggest that cyclosporin A competes with endogenous plasma membrane proteins for association with cyclophilin B in the secretory pathway. These findings argue in favor of a role for cyclophilin B as a chaperone to proteins destined for the plasma membrane, rather than solely as a proline isomerase functioning within the endoplasmic reticulum.

A map of the distal region of the long arm of human chromosome 21 constructed by radiation hybrid mapping and pulsed-field gel electrophoresis

We have used radiation hybrid (RH) mapping and pulsed-field gel electrophoresis (PFGE) to determine the order and positions of 28 DNA markers from the distal region of the long arm of human chromosome 21. The maps generated by these two methods are in good agreement. This study, combined with that of D. R. Cox et al. (1990, Science 250:245-250), results in an RH map that covers the long arm of chromosome 21 (21q). We have used a subtelomeric probe to show that our map includes the telomere and have identified single-copy genes and markers within 200 kbp of the telomere. Comparison of the physical and RH maps with genetic linkage maps shows "hot spots" of meiotic recombination in the distal region, one of which is close to the telomere, in agreement with previous cytogenetic observations of increased recombination frequency near telomeres.

Radiation hybrid mapping: a somatic cell genetic method for constructing high-resolution maps of mammalian chromosomes

Radiation hybrid (RH) mapping, a somatic cell genetic technique, was developed as a general approach for constructing long-range maps of mammalian chromosomes. This statistical method depends on x-ray breakage of chromosomes to determine the distances between DNA markers, as well as their order on the chromosome. In addition, the method allows the relative likelihoods of alternative marker orders to be determined. The RH procedure was used to map 14 DNA probes from a region of human chromosome 21 spanning 20 megabase pairs. The map was confirmed by pulsed-field gel electrophoretic analysis. The results demonstrate the effectiveness of RH mapping for constructing high-resolution, contiguous maps of mammalian chromosomes.

Experimental residency program in veterinary public health

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