Mammary Implants Research Articles

Unraveling the Immune Web: Advances in SMI Capsular Fibrosis from Molecular Insights to Preclinical Breakthroughs

Breast implant surgery has evolved significantly, yet challenges such as capsular contracture remain a persistent concern. This review presents an in-depth analysis of recent advancements in understanding the immune mechanisms and clinical implications associated with silicone mammary implants (SMIs). The article systematically examines the complex interplay between immune responses and capsular fibrosis, emphasizing the pathophysiological mechanisms of inflammation in the etiology of this fibrotic response. It discusses innovations in biomaterial science, including the development of novel anti-biofilm coatings and immunomodulatory surfaces designed to enhance implant integration and minimize complications. Emphasis is placed on personalized risk assessment strategies, leveraging molecular insights to tailor interventions and improve patient outcomes. Emerging therapeutic targets, advancements in surgical techniques, and the refinement of post-operative care are also explored. Despite notable progress, challenges such as the variability in immune responses, the long-term efficacy of new interventions, and ethical considerations remain. Future research directions are identified, focusing on personalized medicine, advanced biomaterials, and bridging preclinical findings with clinical applications. As we advance from bench to bedside, this review illuminates the path forward, where interdisciplinary collaboration and continued inquiry weave together to enhance the art and science of breast implant surgery, transforming patient care into a realm of precision and excellence.

SMI-Capsular Fibrosis and Biofilm Dynamics: Molecular Mechanisms, Clinical Implications, and Antimicrobial Approaches

Silicone mammary implants (SMIs) frequently result in capsular fibrosis, which is marked by the overproduction of fibrous tissue surrounding the implant. This review provides a detailed examination of the molecular and immunological mechanisms driving capsular fibrosis, focusing on the role of foreign body responses (FBRs) and microbial biofilm formation. We investigate how microbial adhesion to implant surfaces and biofilm development contribute to persistent inflammation and fibrotic responses. The review critically evaluates antimicrobial strategies, including preoperative antiseptic protocols and antimicrobial-impregnated materials, designed to mitigate infection and biofilm-related complications. Additionally, advancements in material science, such as surface modifications and antibiotic-impregnated meshes, are discussed for their potential to reduce capsular fibrosis and prevent contracture of the capsule. By integrating molecular insights with clinical applications, this review aims to elucidate the current understanding of SMI-related fibrotic responses and highlight knowledge gaps. The synthesis of these findings aims to guide future research directions of improved antimicrobial interventions and implant materials, ultimately advancing the management of capsular fibrosis and enhancing patient outcomes.

Macrophage Immunomodulation and Suppression of Bacterial Growth by Polydimethylsiloxane Surface-Interrupted Microlines’ Topography Targeting Breast Implant Applications

Since breast cancer is one of the most common forms of cancer in women, silicone mammary implants have been extensively employed in numerous breast reconstruction procedures. However, despite the crucial role they play, their interaction with the host’s immune system and microbiome is poorly understood. Considering this, the present work investigates the immunomodulatory and bacterial mitigation potential of six textured surfaces, based on linear step-like features with various regular and irregular multiscaled arrangements, in comparison to a flat PDMS surface. We hypothesise that the chosen surface geometries are capable of modulating the cellular response through mechanical interdigitation within the multiscaled surface morphology, independent of the surface chemical properties. Each type of sample was characterised from a physico-chemical and biological points of view and by comparison to the flat PDMS surface. The overall results proved that the presence of linear multiscaled step-like features on the PDMS surface influenced both the surface’s characteristics (e.g., surface energy, wettability, and roughness parameters), as well as the cellular response. Thus, the biological evaluation revealed that, to different degrees, biomaterial-induced macrophage activation can be mitigated by the newly designed microtextured surfaces. Moreover, the reduction in bacteria adherence up to 90%, suggested that the topographical altered surfaces are capable of suppressing bacterial colonisation, therefore demonstrating that in a surgical environment at risk of bacterial contamination, they can be better tolerated.

A Multi-Center Retrospective Observational Analysis of Three-Year Experience of Our Protocol for Prevention and Monitoring of Surgical Site Infections in Implant-Based Breast Reconstruction.

With the rise in the mastectomy rate, the number of patients who choose to undergo postmastectomy reconstruction has been increasing, and implant-based procedures are the most performed methods for postmastectomy breast reconstruction. Among the possible complications, the most feared is the loss of reconstruction. It can be related to several reasons, but one of the most common is infection of the implant, which can lead to prolonged antibiotic treatment, undesired additional surgical procedures, increased incidence of capsular contracture, and unsatisfactory aesthetics results, with a huge psychological impact on patients. The primary intent of this study is to analyze the status of infection rates at our institution and evaluate the effectiveness of our prevention protocol since its introduction. Secondly, we compared data of the surgical site infections (SSIs) after implant-based breast reconstruction at Trieste Hospital, where the protocol has been employed since 2020, and in another center, where plastic surgeons of our team are involved, with different prevention procedures. We enrolled 396 female patients, who underwent implant-based breast reconstruction, using definitive mammary implants or breast tissue expanders, with or without ADM (acellular dermal matrix), both for breast cancer and risk-reducing surgery in BRCA1/2 patients. Patients treated at the Hospital of Trieste, with the use of the prevention protocol, were considered the experimental group (group 1), while patients treated in Gorizia by the same breast team with standardized best-practice rules, but without the use of the prevention protocol, were considered the control group (group 2). Infected patients were 5 in the first group (1.7%) and 8 in the second one (7.9%), with a global infection rate of 3.2%. After the introduction of our prevention protocol, we faced a lower incidence of infection after breast surgery with implants or tissue expanders.

A new Neu—a syngeneic model of spontaneously metastatic HER2-positive breast cancer

Metastatic disease results from the dissemination of tumor cells beyond their organ of origin to grow in distant organs and is the primary cause of death in patients with advanced breast cancer. Preclinical murine models in which primary tumors spontaneously metastasize are valuable tools for studying metastatic progression and novel cancer treatment combinations. Here, we characterize a novel syngeneic murine breast tumor cell line that provides a model of spontaneously metastatic neu-expressing breast cancer with quicker onset of widespread metastases after orthotopic mammary implantation in immune-competent NeuN mice. The NT2.5-lung metastasis (-LM) cell line was derived from serial passaging of tumor cells that were macro-dissected from spontaneous lung metastases after orthotopic mammary implantation of parental NT2.5 cells. Within one week of NT2.5-LM implantation, metastases are observed in the lungs. Within four weeks, metastases are also observed in the bones, spleen, colon, and liver. We demonstrate that NT2.5-LM metastases are positive for NeuN—the murine equivalent of human epidermal growth factor 2 (HER2). We further demonstrate altered expression of markers of epithelial-to-mesenchymal transition (EMT), suggestive of their enhanced metastatic potential. Genomic analyses support these findings and reveal enrichment in EMT-regulating pathways. In addition, the metastases are rapidly growing, proliferative, and responsive to HER2-directed therapy. The new NT2.5-LM model provides certain advantages over the parental NT2/NT2.5 model, given its more rapid and spontaneous development of metastases. Besides investigating mechanisms of metastatic progression, this new model may be used for the rationalized development of novel therapeutic interventions and assessment of therapeutic responses.

Silicone implant surface microtopography modulates inflammation and tissue repair in capsular fibrosis.

Excessive fibrous capsule formation around silicone mammary implants (SMI) involves immune reactions to silicone. Capsular fibrosis, a common SMI complication linked to host responses, worsens with specific implant topographies. Our study with 10 patients investigated intra- and inter-individually, reduced surface roughness effects on disease progression, wound responses, chronic inflammation, and capsular composition. The results illuminate the significant impact of surface roughness on acute inflammatory responses, fibrinogen accumulation, and the subsequent fibrotic cascade. The reduction of surface roughness to an average roughness of 4 μm emerges as a promising approach for mitigating detrimental immune reactions, promoting healthy wound healing, and curbing excessive fibrosis. The identified proteins adhering to rougher surfaces shed light on potential mediators of pro-inflammatory and pro-fibrotic processes, further emphasizing the need for meticulous consideration of surface design. The composition of the implant capsule and the discovery of intracapsular HSP60 expression highlight the intricate web of stress responses and immune activation that can impact long-term tissue outcomes.

Surface Topography, Microbial Adhesion, and Immune Responses in Silicone Mammary Implant-Associated Capsular Fibrosis.

Breast cancer is the most common cancer in women globally, often necessitating mastectomy and subsequent breast reconstruction. Silicone mammary implants (SMIs) play a pivotal role in breast reconstruction, yet their interaction with the host immune system and microbiome remains poorly understood. This study investigates the impact of SMI surface topography on host antimicrobial responses, wound proteome dynamics, and microbial colonization. Biological samples were collected from ten human patients undergoing breast reconstruction with SMIs. Mass spectrometry profiles were analyzed for acute and chronic wound proteomes, revealing a nuanced interplay between topography and antimicrobial response proteins. 16S rRNA sequencing assessed microbiome dynamics, unveiling topography-specific variations in microbial composition. Surface topography alterations influenced wound proteome composition. Microbiome analysis revealed heightened diversity around rougher SMIs, emphasizing topography-dependent microbial invasion. In vitro experiments confirmed staphylococcal adhesion, growth, and biofilm formation on SMI surfaces, with increased texture correlating positively with bacterial colonization. This comprehensive investigation highlights the intricate interplay between SMI topography, wound proteome dynamics, and microbial transmission. The findings contribute to understanding host-microbe interactions on SMI surfaces, essential for optimizing clinical applications and minimizing complications in breast reconstruction.

Immediate prepectoral versus submuscular breast reconstruction in nipple-sparing mastectomy: a retrospective cohort analysis.

To evaluate early complications in prepectoral breast reconstruction. A retrospective cohort study including 180 consecutive cases of nipple-sparing mastectomy, comparing immediate breast reconstruction with subpectoral to prepectoral mammary implants in 2012-2022. Clinical and demographic characteristics and complications in the first three months following surgery were compared between the two techniques. The prepectoral technique was used in 22 cases (12.2%) and the subpectoral in 158 (87.8%). Median age was higher in the prepectoral group (47 versus 43.8 years; p=0.038), as was body mass index (25.1 versus 23.8; p=0.002) and implant volume (447.5 versus 409 cc; p=0.001). The prepectoral technique was more associated with an inframammary fold (IMF) incision (19 cases, 86.4% versus 85, 53.8%) than with periareolar incisions (3 cases, 13.6% versus 73, 46.2%); (p=0.004). All cases in the prepectoral group underwent direct-to-implant reconstruction compared to 54 cases (34.2%) in the subpectoral group. Thirty-eight complications were recorded: 36 (22.8%) in the subpectoral group and 2 (9.1%) in the prepectoral group (p=0.24). Necrosis of the nipple-areola complex/skin flap occurred in 27 patients (17.1%) in the subpectoral group (prepectoral group: no cases; p=0.04). The groups were comparable regarding dehiscence, seroma, infection, and hematoma. Reconstruction failed in one case per group (p=0.230). In the multivariate analysis, IMF incision was associated with the prepectoral group (aOR: 34.72; 95%CI: 2.84-424.63). The incidence of early complications was comparable between the two techniques and compatible with previous reports. The clinical and demographic characteristics differed between the techniques. Randomized clinical trials are required.

Quantitative Proteomic Characterization of Foreign Body Response towards Silicone Breast Implants Identifies Chronological Disease-Relevant Biomarker Dynamics.

The etiology of exaggerated fibrous capsule formation around silicone mammary implants (SMI) is multifactorial but primarily induced by immune mechanisms towards the foreign material silicone. The aim of this work was to understand the disease progression from implant insertion and immediate tissue damage response reflected in (a) the acute wound proteome and (b) the adsorption of chronic inflammatory wound proteins at implant surfaces. An intraindividual relative quantitation TMT-liquid chromatography-tandem mass spectrometry approach was applied to the profile wound proteome formed around SMI in the first five days post-implantation. Compared to plasma, the acute wound profile resembled a more complex composition comprising plasma-derived and locally differentially expressed proteins (DEPs). DEPs were subjected to a functional enrichment analysis, which revealed the dysregulation of signaling pathways mainly involved in immediate inflammation response and ECM turnover. Moreover, we found time-course variations in protein enrichment immediately post-implantation, which were adsorbed to SMI surfaces after 6-8 months. Characterization of the expander-adhesive proteome by a label-free approach uncovered a long-term adsorbed acute wound and the fibrosis-associated proteome. Our findings propose a wound biomarker panel for the early detection and diagnosis of excessive fibrosis that could potentially broaden insights into the characteristics of fibrotic implant encapsulation.

Intramammary rapamycin administration to calves induces epithelial stem cell self-renewal and latent cell proliferation and milk protein expression

Mammary epithelial stem cells differentiate to create the basal and luminal layers of the gland. Inducing the number of differentiating bovine mammary stem cells may provide compensating populations for the milk-producing cells that die during lactation. Inhibition of mTOR activity by rapamycin signals self-renewal of intestinal stem cells, with similar consequences in the mouse mammary gland and in bovine mammary implants maintained in mice. The implementation of these results in farm animals for better mammary development and production was studied in 3-month-old calves. mTOR activity decreased by ~50% in mammary epithelial cells subjected to 3-week rapamycin administration, with no negative consequences on mammary morphology or β-casein expression. Subsequently, stem cell self-renewal was induced, reflected by a higher propagation rate of cultures from rapamycin-treated glands compared to respective controls and higher expression of selected markers. Followed by 4-day estrogen and progesterone administration, rapamycin significantly induced proliferation rate. Higher numbers of basal and luminal PCNA+ cells were detected in small ducts near the elongating sites as compared to large ducts, in which only luminal cells were affected. Rapamycin administration resulted in induction of individual milk protein genes' expression, which was negatively correlated to their endogenous levels. The inductive effect of rapamycin on luminal cell number was confirmed in organoid cultures, but milk protein expression decreased, probably due to lack of oscillation in rapamycin levels. In conclusion, intramammary rapamycin administration is an effective methodology to reduce mTOR activity in bovine mammary epithelial cells and consequently, induce stem cell self-renewal. The latent positive effect of rapamycin on epithelial cell proliferation and its potential to improve milk protein expression in calves may have beneficial implications for mature cows.

Mammary tumors alter the fecal bacteriome and permit enteric bacterial translocation

BackgroundCancer patients experience gastrointestinal and behavioral symptoms, and are at increased risk of systemic infection and inflammation. These conditions are a major source of morbidity and decreased quality of life prior to cancer treatment, but poorly defined etiologies impede successful treatment. The gastrointestinal microbiota shape inflammation, influence cancer progression and treatment, and colonize tumors. However, research has not directly determined if peripheral tumors influence the microbiome and intestinal physiology, thus influencing gastrointestinal and behavioral symptoms. Therefore, the purpose of this study was to examine consequences of orthotopic, syngeneic mammary tumor implantation, growth, and resection on fecal bacteriome composition and intestinal barrier function in relation to systemic inflammation and enteric bacterial translocation in mice.MethodsFemale mice were randomized to 3 experimental groups: sham surgical control, tumor recipients, and tumor recipients later receiving tumor-resection. Mice were sacrificed three weeks after tumor implantation or resection for collection of stool, colon, spleen, and brain tissue and analysis.ResultsTumor-bearing mice exhibited several markers of colonic barrier disruption, including dampened expression of tight junction proteins (Cldn1 and Ocln) and elevated circulating lipopolysaccharide binding protein (LBP). Compromised colonic barrier integrity was associated with altered fecal bacterial profiles in tumor-mice, including lower relative abundance of Lactobacillus, but higher Bacteroides. Consistent with colonic barrier disruption and altered microbiomes, tumor-mice displayed markers of systemic inflammation including splenomegaly, higher splenic bacterial load, and elevated splenic and brain pro-inflammatory cytokines. Several bacteria cultured from spleens had 16S rRNA gene amplicons matching those in fecal samples, suggesting they were of intestinal origin. Fecal Lactobacillus was highly-interrelated to physiological parameters disrupted by tumors via correlation network analysis. Tumor resection ameliorated circulating LBP, splenomegaly, and splenic cytokines, but not other parameters associated with loss of colonic barrier integrity and bacterial translocation.ConclusionsOrthotopic mammary tumors alter the microbiome, reduce intestinal barrier function, increase translocation of enteric bacteria, and alter systemic inflammation. This provides insight into how tumors commence gastrointestinal and behavioral symptoms prior to treatment, and identify targets for future therapeutics, such as probiotic Lactobacillus supplementation.

Abstract PD14-07: Bromodomain and Extra-Terminal motif (BET) inhibitors are a rational therapeutic choice for treatment of invasive lobular carcinoma

Abstract Invasive lobular carcinoma (ILC) is the second most common type of breast cancer accounting for approximately 10-15% of all breast tumours. ILC is characterized by inactivation of E-Cadherin and cancer cells that invade the stroma in a "single-file" pattern. Women with ILC are more likely to have hormone receptor-positive disease. ILCs are three times more likely to metastasize to the peritoneum, gastrointestinal tract, and ovaries. ILC are currently treated in the same manner as all other ER+ breast cancers. Like invasive ductal carcinoma (IDC), anti-estrogen resistance has emerged as a significant problem in the management of ILC. Approximately half of the recurrences of ER+ breast tumors respond to anti-endocrine treatment, while the other half are resistant. Additionally, anti-estrogen-resistant breast tumor cells appear to have/acquire a more aggressive, invasive phenotype compared to their anti-estrogen-responsive counterparts. ILC is considered to be chemo-resistant and ILC patients receive no additional benefit from adjuvant chemotherapy. As such, there is a pressing need to develop tailored therapeutic options for endocrine-resistant ILC patients. The bromodomain and extra-terminal (BET) motif family are epigenetic readers that bind to acetylated histones, recruiting co-factors to regulate transcription. As part of the FP7 RATHER project aimed at identifying rational treatment options for ILC, we discovered that BRD3 (uniquely among the BET family members) is a marker of poor prognosis in ILC but not in ER+ breast cancers as a whole. We subsequently validated this in an independent cohort from the METABRIC study. These data suggest that Brd3 may play a significant role in tumour progression in ILC and may be a rational therapeutic target for lobular tumours. Using the two ILC cell lines SUM44PE (SUM44) and MDA MB 134 VI (MM134) previously shown to be anti-endocrine resistant we assessed the therapeutic potential of BET inhibition. We found that ILC cell lines that do not respond to anti-endocrine therapy are sensitive to a panel of BET inhibitors in both 2D and 3D assays. In particular the BET inhibitors JQ1 and Mivebresib had the highest potency, these BET inhibitors were selected for further research. Next, a multi-omics approach merging RNA-sequencing with mass spectrometry was utilised to dissect the transcriptional networks employed by BET inhibitors in this ILC setting. RNA-sequencing revealed dysregulated pathways in cell cycle division, DNA damage, apoptosis and MAPK signalling following treatment. Further, rapid immunoprecipitation mass spectrometry of endogenous proteins (RIME) was carried out to find the binding partners of the BRD proteins. Integrated pathway analysis through Genome Enhancer was used to assess the master regulators (MTRs) which drive BET inhibitor function. There was 142 MTRs found across the two cell lines treated with both inhibitors. Of note the MTR, FGFR3, was shown to regulate the downstream targets of both BET inhibitors. Further analysis of BET inhibition combined with erdafitinib, an FGFR inhibitor, drives increased cell inhibition compared to either agent alone. Finally, the efficacy of JQ1 in targeting ILC was assessed in vivo. We utilised the ILC cell-derived xenograft (CDX) models established by mammary intraductal implantation. The efficacy of BET inhibition alone and in combination with anti-endocrine therapies, tamoxifen and fulvestrant were assessed in the MM134 cell line. We found that JQ1 works synergistically with tamoxifen to significantly decrease tumour burden and metastatic potential in this tamoxifen resistant ILC model. Taken together this data highlights the need for tailored therapeutics in ILC research and highlights the use of BET inhibition in the anti-endocrine resistant ILC setting. Citation Format: Elspeth Ward, Anna Blümel, Emer Conroy, Grainne Cremin, Binbin Gao, William Gallagher, Idalia Cruz, Leena Hilakivi-Clarke, George Sflomos, Cathrin Brisken, Darran O'Connor. Bromodomain and Extra-Terminal motif (BET) inhibitors are a rational therapeutic choice for treatment of invasive lobular carcinoma [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr PD14-07.

Biofilm Formation on Breast Implant Surfaces by Major Gram-Positive Bacterial Pathogens.

Bacterial biofilm on surfaces of mammary implants is a predisposing factor for several outcomes. Because Gram-positive bacteria are potential agents of biomaterial-associated infections (BAIs), their abilities to form biofilm on breast implants should be elucidated. The aim of this study was to evaluate biofilm formation on different mammary prosthesis surfaces by major Gram-positive bacterial pathogens involved in BAIs. We initially evaluated biofilm formation on polystyrene plates with and without fibrinogen or collagen for 1 reference strain and 1 clinical isolate of Enterococcus faecalis, Staphylococcus aureus, Staphylococcus epidermidis, and Streptococcus pyogenes. We also tested the ability of clinical isolates to form biofilm on 4 different implant surfaces: polyurethane foam and smooth, microtextured, and standard textured silicone. Biofilm structure and cell viability were observed by scanning electron microscopy and confocal laser scanning microscopy. All strains showed strong biofilm formation on polystyrene. After fibrinogen or collagen treatment, biofilm formation varied. With fibrinogen, reference strains of S. aureus and S. pyogenes increased biofilm formation (P < 0.05). Reference strains of all species and the clinical isolate of S. pyogenes increased biofilm formation after collagen treatment (P < 0.05). In general, S. aureus showed higher capacity to produce biofilm. Scanning electron microscopy showed that biofilm attached to all surfaces tested, with the presence of extracellular polymeric substances and voids. Viable cells were more frequent for E. faecalis and S. pyogenes. All species produced biofilm on all prosthesis surfaces and under different conditions. Micrographies indicated thicker bacterial biofilm formation on microtextured and/or standard textured silicone by all species, except E. faecalis.

Abstract 1672: Comparing subcutaneous to mammary fat pad implantation on the growth kinetics, histology and drug response of PDX breast cancer models

Abstract Preclinical oncology studies frequently use patient-derived xenograft (PDX) tumor models and the efficacy of the test therapy is evaluated by measuring changes in tumor volume. Subcutaneous (SQ) implantation of tumors is most widely used in oncology studies due to ease of technique and tumor accessibility for caliper measurements. However, SQ tumors are then growing in a different environment compared to the tumor model. Conversely, orthotopic implantation provide tumors with a similar microenvironment for growth, but require surgical techniques which increase the amount of resources, time, and skill needed to perform these studies. Currently, the standard method for an orthotopic breast cancer involves surgically clearing the mammary fat pad (MFP) prior to engrafting the cells or tissue. In this study we developed a nonsurgical approach where PDX tissue is engrafted directly into a non-cleared MFP using a method similar to SQ engraftment. Using several different established breast cancer PDX models, this study compares the impact of SQ and MFP implantation on growth kinetics, tumor histology and drug efficacy. For each experiment, 8-week old female NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ (NSG; JAX strain #005557) mice were shaved on the right flank or MFP, earnotched and housed. PDX breast tumor tissue from donor mice was cleared of necrotic tissue and mouse tissue, minced and loaded into syringes capped with either 14G or 18G trocar needles. Mice were put under anesthesia and trocared with 50ul of PDX breast tumor model tissue. Non-cleared implantations were performed in all groups and tumor models. Tumor growth was monitored using caliper measurements until the study terminus. Slides generated from formalin-fixed and paraffin embedded tumor tissue were used for histological analysis. Cisplatin and Docetaxel were selected as standard of care agents to compare drug responses in SQ versus MFP engrafted tumors. In all tested models, tumors volumes in the MFP cohort are significantly higher compared to tumors implanted SQ. Tumors engrafted into the MFP reached 500mm3 significantly earlier than tumors engrafted SQ, but the doubling times remained unchanged. This suggests the environment of the MFP allows for a faster engraftment rather than a shorter doubling time. H&amp;E staining shows no significant histological difference between tumor models engrafted in the SQ and MFP for this study. This likely because tumor models were established in the SQ for at least 3 rounds of engraftment before being engrafted in the MFP for this study. Histological differences may have been prominent if the tumor models were established in the appropriate locations (SQ or MFP) at model development. This study has important implications for ensuring a more clinically relevant growth environment for mouse studies using PDX breast models. Citation Format: Kyle M. Draheim, Raphaela R. Banzon, Marta M. Tewodros, Daniel VanBuskirk, Mingshan Cheng. Comparing subcutaneous to mammary fat pad implantation on the growth kinetics, histology and drug response of PDX breast cancer models [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1672.

Subclinical Infection of the Silicone Breast Implant Surface as a Possible Cause of Capsular Contracture.

In order to reexamine the possible association between bacterial presence and capsular contracture, 55 silicone devices (mammary implants or tissue expanders) were cultured at the time of their removal from 40 patients. Special culture techniques were used in an attempt to recover bacteria adhering to the smooth-surfaced implant and encased in glycocalyx biofilm. Bacteria were detected on 56% (15 of 27) of implants surrounded by contracted capsules and on 18% (5 of 28) of those without capsular contracture (p < 0.05). Only three implants tested positive using routine plating techniques. The predominant isolate was Staphylococcus epidermidis. The concept that capsular contracture is associated with subclinical infection of silicone implants is supported by this study. With changes in the microbiological technique, bacterial recovery and growth occurs at a frequency greater than previously thought.

Comparison between Immediate and Delayed Prosthetic Breast Reconstruction Following Mastectomy

Abstract Purpose to compare the outcomes of Immediate versus Delayed prosthetic breast reconstruction. Together with highlighting the importance of immediate reconstruction when it is feasible. Materials and methods This was a prospective study that was held at ain shams university hospitals and Helwan university hospital. The study included 20 patients who were planned to undergo a mastectomy either unilateral or bilateral, patients were divided equally in to 2 groups, (Group A) had an immediate breast reconstruction using mammary implants, while (Group B) had a delayed breast reconstruction using tissue expander then replacing it after a few months with a mammary implant, and the post operative complications were compared against each other. Results Although the number of complications were more in (Group A), but statistically it was found that the rate of complications after immediate reconstruction was non significant from after delayed reconstruction. Conclusion both immediate and delayed mastectomy reconstruction provide substantial safety and quality of life benefits for women choosing these procedures. Furthermore, patients who postpone reconstruction after mastectomy due to personal preference or by medical necessity can be reassured that this approach is a safe alternative to immediate reconstruction and can provide equivalent quality of life and body image benefits.

Abstract P6-06-11: The inhibition of leptin receptor impairs macrophage recruitment in the tumor microenvironment blocking breast cancer growth and progression

Abstract Background: Breast tumorigenesis results from the sequential acquisition of multiple genetic alterations in the epithelial cells and is also influenced by reciprocal interactions between the tumor cells and the surrounding stromal microenvironment. In this regard, an important mediator in driving mammary tumorigenesis is leptin, mainly secreted by adipocytes, but also by other cells in the tumor microenvironment. Several studies support the crucial involvement of leptin/leptin receptor (ObR) in the biology of breast cancer; however it still remains to be elucidated how ObR signaling may modulate tumor cell cytokine secretion favoring a permissive microenvironment required for tumor progression. Thus, we evaluated the impact of ObR lack in affecting breast cancer phenotype and in mediating epithelial/stromal tumor reciprocal interaction by using both in vitro and in vivo experimental approaches. Methods: As experimental models we established stable ERα-positive MCF-7 with an empty lentiviral vector (MCF-7 EV) and a lentiviral vector to silence human ObR (MCF-7 shObR), triple-negative MDA-MB-231 and human monocyte cell line derived from an acute monocyte leukemia patient, THP-1. We ran cytokine array to study cytokine secretion pattern in both MCF-7 EV and MCF-7 shObR cells. qRT-PCR, immunofluorescence and ELISA were performed to detect MCP-1 expression and secretion. Co-culture experiments and Boyden Chamber Transmigration assays were assessed to study the recruitment of THP1. Tumor associated macrophage (TAM) markers were detected after co-colture experiments between MCF-7 stable clones, MDA-MB-231 cells and THP1. Orthotopic mammary fat pad implantation of MCF-7 stable clones was performed to test tumor growth and macrophage infiltration. Results: Firstly we demonstrated a reduced activation of leptin signaling, and a decreased growth and motility in MCF-7 shObR cells compared to MCF-7 EV. Cytokine array revealed that the lack of ObR abrogated the release of monocyte chemoattractant protein (MCP1), and dramatically down-regulated interleukin 8 (IL-8) and intercellular adhesion molecule 1 (ICAM-1) secretion. Moreover, in MCF-7 shObR cells we found a diminution of MCP-1 in terms of mRNA and protein expression. As expected the suppression of MCP-1 secretion in these cells blocked the recruitment of monocytes and inhibited TAM development. The specific role of ObR/Ob signaling in regulating MCP-1 expression and secretion was further demonstrated in the presence of the ObR selective antagonist, the LDFI. LDFI treatment markedly down-regulated MCP-1 expression thus blocking macrophage recruitment and polarization in MDA-MB-231 cells. In vivo experiments revealed a decrease of tumor growth in MCF-7 shObR cells compared to MCF-7 EV wherein a dramatic reduction of MCP-1 expression was well reproduced in MCF-7 shObR clones. Conclusions: Our results, for the first time, showed that Ob/ObR signaling pathway may directly control MCP-1 function and tumor cell-polarized macrophages. Thus these data suggest the use of leptin receptor specific antagonist able to block macrophage-mediated effects of tumor microenvironment in sustaining breast cancer growth and progression. Citation Format: Luca Gelsomino, Salvatore Panza, Giuseppina Augimeri, Giuseppina Daniela Naimo, Rocco Malivindi, Giusi La Camera, Alessandro Paolì, Cinzia Giordano, Ines Barone, Loredana Mauro, Daniela Bonofiglio, Stefania Catalano, Sebastiano Andò. The inhibition of leptin receptor impairs macrophage recruitment in the tumor microenvironment blocking breast cancer growth and progression [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P6-06-11.

Abstract A012: Mammary fat pad injections: An alternative implantation method for syngeneic tumor models

Abstract Syngeneic tumor models used for discovery of immune therapeutics should have several features such as a long study duration, responsiveness to checkpoint inhibitors, high immune cell infiltration and a high homogeneity in tumor growth. Moreover, models should consider the ethical rules (3R reduce, refine, replace). At present, the standard implantation method for syngeneic tumor models is subcutaneous tumor cell inoculation. We have developed an alternative implantation method for syngeneic tumor models: inoculation into the mammary fat pad. Both implantation sides are heterotopic related to the original tumor entity except for syngeneic breast tumor cells. In addition, both tumor inoculation methods can easily be applied and monitored by calipering reducing the costs. We compared the two implantation methods with models MC38-CEA, Ct26wt, Hepa1-6, RENCA, LL-2, AB12, CloneM3, B16.F10, 4T1 and EMT-6 tumor cells in respect to growth characteristics and immune response. Intra-mammary tumor growth showed more homogeneity with higher final tumor volumes compared to the subcutaneous tumor growth. Moreover, in all tested syngeneic models, tumor ulceration was prevented by almost 100% when injecting the tumor cells into the mammary fat pad. In contrast, animals of the subcutaneous tumors were mainly euthanized due to tumor ulceration. Both findings favor the mammary fat pad injection with regard to the 3R rules by strongly reducing tumor ulceration (refinement) and animal number due to a more homogenous growth (reduction). In addition, the immune checkpoint inhibitor treatment was tested and found comparable between the intra-mammary and subcutaneous models. The presence of immune cell populations was investigated in the Ct26wt colon tumor model time-dependently by flow cytometry using a 17 marker-staining panel . The number of isolated cells per gram tumor mass was more than doubled in the intra-mammary tumors. In conclusion, tumor models of the heterotopic intra-mammary implantation side are found to be superior compared to the traditional subcutaneous tumor models: a higher tumor homogeneity with no tumor ulceration, combined with a high number of immune cells and connective stroma tissue, making the mammary fat pad implantation of syngeneic tumor cells the implantation side of choice. Citation Format: Cynthia Obodozie, Susanne Ruf, Gojko Bijelic, Sandra Moor, Bianca Giesen, Ulrike Leisegang, Sebastian Dempe, Holger Weber. Mammary fat pad injections: An alternative implantation method for syngeneic tumor models [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr A012. doi:10.1158/1535-7163.TARG-19-A012

Calorie restriction and rapamycin administration induce stem cell self-renewal and consequent development and production in the mammary gland

Expansion of the mammary epithelial stem cell pool holds promise for consequent mammary gland development and production. Complementary analyses of bovine mammary implants maintained in de-epithelialized mouse mammary fat pad and endogenous mouse mammary gland were performed to elucidate the effect of calorie restriction (CR) on stem cell self-renewal. CR elevated propagation rate and non-adherent mammosphere generation in cultured bovine mammary cells. A corresponding decrease in progenitor-induced colony formation and differentiation marker expression was noted. In the mouse gland, CR enhanced the take rate of transplanted cells and outgrowths' fat pad occupancy. Downregulating mTOR activity by rapamycin administration reproduced CR's effects on stem cell self-renewal within a shorter period. Flow cytometry demonstrated a significant 1.5-fold increase in stem cell number and a corresponding decrease in luminal progenitor and differentiated cells. Consequent effects of rapamycin administration included enhanced ductlet generation in bovine implants and higher milk-protein gene expression in cultured mouse mammary cells. The stimulatory effect of CR on BST-1 expression in both bovine implants and mouse glands resembled that noted in the intestinal Paneth stem cell niche (Yilmaz et al., 2012). A putative niche may also exist in the mammary gland, conveying energy-status information to the insulated stem cells.

Five-Year Retrospective Analysis of Eurosilicone's Silicone Gel-Filled Breast Implants.

BackgroundSilicone breast implants have been widely used for breast augmentation and reconstruction. During this time, silicone breast implants have undergone several modifications to improve their safety, quality, and clinical performance. Complications such as reoperation, capsular contracture, and rupture are risks often associated with breast implants.ObjectivesThe authors conducted a retrospective study to analyze and report complication rates associated with Eurosilicone’s (Eurosilicone S.A.S, Apt, Cedex, France) silicone gel–filled breast implants over a period of 5 years.MethodsIn this retrospective clinical study, 2151 women who underwent either breast augmentation or breast reconstruction with Eurosilicone breast implants were diagnosed. Data on early and late complications including implant removal (explantation/exchange), capsular contracture, and rupture were collected using questionnaires, completed by 39 surgeons across Italy.ResultsOf the 2151, only 60 patients (2.78%) required implant removal. Twenty-five patients experienced capsular contracture (Baker Grade III/IV), giving an actual rate of 1.2%. The actual rate of implant rupture confirmed by breast magnetic resonance images was 0.18% (4 implants). Six patients (0.27%) were diagnosed with breast cancer following breast augmentation, and local complications including hematoma (1 patient) and seroma (2 patients) were experienced.ConclusionsThis retrospective clinical study involving Eurosilicone’s round and anatomical textured silicone gel–filled mammary implants demonstrates an excellent safety profile through 5 years. Level of Evidence: 2