The effect of lipoaspirates vs. dissected abdominal fat on breast cancer cells in vitro
© The Author(s) 2017
Received: 12 September 2016
Accepted: 7 March 2017
Published: 21 March 2017
Cancer cells are typically surrounded by stromal cells and embedded in extracellular matrix (ECM). The stromal compartment interacts with cancer cells to promote growth and metastasis. For decades, autologous fasciocutaneous flaps have been safely applied for breast reconstruction after mastectomy. In contrast, the safety of fat grafting (lipofilling) procedure has been under debate regarding the risk of cancer recurrence.
Harvested fat tissue (lipoaspirates) and dissected abdominal fat (DAF) were co-cultured with MCF-7 breast cancer cells. The vitality of MCF-7 cells was measured using AlamarBlue® consecutively for 5 days. ECM degradation was determined by detection of matrix metalloproteinase-1 (MMP-1) expression in MCF-7 cells. Integrin α2 was measured by Western blot to assess the degree of adhesion and motility of MFC-7 cells.
The MCF-7 proliferation increased substantially when co-cultured with fat tissue. However, there was no significant difference between the proliferation stimulating effects of lipoaspirates and DAF. Similarly, MMP-1 protein expression was equally elevated in MCF-7 cells by both lipoaspirates and DAF. Importantly, MCF-7 cells showed an increased level of integrin α2 once co-cultured with either lipoaspirates or DAF.
Fat tissue increases the proliferation of MCF-7 cells in vitro. Our data suggest that lipoaspirates as well as DAF might possess a considerable potency to promote tumorigenic growth of breast cancer cells. Thus, clinical trials are needed to address the safety of lipofilling by breast reconstruction surgery after mastectomy.
KeywordsFat grafting Breast cancer Breast reconstruction
Cancer cells are typically surrounded by stromal cells like mesenchymal, inflammatory and vascular cells. Stromal cells support cancer cells by providing mediators for cell proliferation, inflammation and angiogenesis . In addition, cancer cells are embedded in extracellular matrix (ECM), which plays crucial roles in modulation of stromal compartment and cancer cell invasion. Modulation of the stromal compartment is exerted by matrix metalloproteinases (MMPs) . MMPs are involved in many physiological and pathological processes in the human body, which are normally present in tissues at low levels and increase dramatically during any changes [3, 4]. Overexpression and activation of MMPs have been implicated in pathological cleavage of connective tissue by arthritis , cardiovascular disease , and tumor progression . However, the process of metastases is complex. In order to migrate, cell adhesion and motility molecules are required, after cleavage of the connective tissue, to interact with ECM as well as vascular endothelium to the secondary site [8, 9]. Integrin is a family of transmembrane receptors consist of α and β subunits and serves as cell–cell as well as cell–matrix adhesion molecule . In normal and tumor cells, integrins have a central function in intracellular signaling pathways that lead to cell proliferation, differentiation and migration .
After initial breast cancer surgery like mastectomy or breast conserving surgery and subsequent oncological therapy, up to 95.5% of these women are considered for breast reconstruction including prosthetic implants and flaps . The latter represents a wide variety of options such as myocutanoeus flaps, e.g., the latissimus dorsi  as a regional flap, and muscle-sparing Transvers Rectus Abdominis Myocutaneous flap “msTRAM” as a free tissue transfer . The Deep Inferior Epigastric artery Perforator flap ‘DIEP’ from the abdominal wall has also been successfully applied for breast reconstruction . DIEP flaps provide a homogenous rounded breast and are currently considered as a safe procedure in the oncological aspect and referred to as the “gold standard” by many authors [15, 16].
Since the initial report  in 1987, autologous grafting of suspended adipose tissue (lipofilling) has become increasingly popular for cosmetic purposes and breast reconstruction worldwide. Concurrently, the American Society of Plastic Surgeons (ASPS) criticized this method of fat grafting that can compromise breast cancer detection . Nowadays, many plastic surgeons question the safety of the procedure as well, discuss the amount of fat tissue reabsorption and doubt the screening results because of micro-calcification . Ultimately, it remains unknown whether autologous fat grafting enhances the breast cancer recurrence or even initiates it at the first place. Adipose tissue and importantly lipoaspirates is a rich source of growth factors, like basic fibroblast growth factor (bFGF), insulin-like growth factor 1 (IGF-1), vascular endothelial growth factor (VEGF), and platelet-derived growth factor (PDGF-BB) . Besides, mature adipocytes are able to produce considerable amounts of estrogen via aromatase-mediated conversion of androgen to estrogen. All these factors are able to potentiate the growth of breast carcinoma cells through a paracrine mechanism [21–24]. Indeed, obesity and weight gain in adult females correlate with an increasing risk of breast cancer . Yet, it remains unclear whether dissected abdominal fat 'en bloc' (DAF) and suspended adipose cells like lipoaspirates differ in their abilities to stimulate tumor growth and invasion.
Within this study, we observed and compared the effects of harvested fat (lipoaspirates) and DAF on breast cancer cells in vitro. We measured the proliferation of the human breast cancer cells line MCF-7 co-cultured with lipoaspirates or DAF. MMP-1 and integrin α2 expression of tumor cells were also detected in both circumstances.
All surgical procedures took place in the Department of Plastic Surgery, Hand Surgery, and Burn Center at RWTH University Hospital, Aachen, Germany. Each patient signed the consent form. The protocol and the use of human materials were approved by the ethics committee of the Faculty of Medicine at RWTH University in Aachen, Germany (Name in German: Ethik-Kommission des Universitätsklinikums Aachen, Votum Number: EK206/13). The experiments were carried out in compliance with Declaration of Helsinki in its current form.
The human breast cancer cell line MCF-7 was obtained from the American Type Culture Collection [HTB 22; derived from a breast adenocarcinoma of 69-year-old Caucasian woman]. MCF-7 cells were maintained in RPMI 1640 supplemented with 5 ml of Minimal Essential Medium non-essential amino acids (NEAA) [PAA, Linz, Austria], 1 mM sodium pyruvate [PAA, Linz, Austria], 1% penicillin and 1% streptomycin [PAA, Linz, Austria], 10 µg/ml human insulin [Biochrom AG, Berlin, German], and 1 or 10% FCS [PAA, Linz, Austria]. Cells were cultured at 37 °C in a humidified atmosphere of 5% CO2.
Proliferation of MCF-7 cells was daily monitored using AlamarBlue® dye [Life technologies]. This dye is a redox indicator that yields a colorimetric change and a fluorescent signal in response to metabolic activity of cells. The inserts holding fat tissue samples were removed before the assay and kept in pre-warmed medium. The MCF-7 culture medium was adjusted to 1 ml in each well and 100 µl of the AlamarBlue® reagent was added to each well. MCF-7 cell were incubated at 37 °C and 5% CO2 for 2 h and subjected to fluorescence measurement. After data collection, the reagent was replaced by fresh medium and the inserts with fat tissue samples were placed back to the corresponding well of MCF-7 cells. After 5 days, cells were harvested and all samples (medium, fat tissue and cell lysates) were kept by −80 °C for further analysis.
Matrix metalloproteinase-1 expression in MCF-7 cells was measured using an ELISA kit according to the manufacturer’s instructions and in two parallel independent experiments [Human Total MMP-1 DuoSet “DY901”, R&D Systems, Minneapolis, MN, USA]. The obtained data were normalized to the total protein concentration. Mean value of the two independent experiments is presented in corresponding figures in this study.
Integrin α2 expression in MCF-7 cells was detected by Anti-Integrin α2 antibodies using Western blot according to the manufacturer’s instructions and in two parallel independent experiments [Anti-Integrin alpha 2 antibody (EPR5789), Abcam plc, Cambridge, UK]. Blots were detected with the LAS-3000 image analyzer (Fujifilm) and protein bands were quantified densitometrically using AIDA software (raytest). Relative protein levels were obtained by normalization to Tubulin. Mean value of the two independent experiments is presented in corresponding figures in this study.
Values are expressed as the arithmetic mean ± standard error of mean (SEM). All assays were performed in duplicate at two different times. The statistical significance of differences between groups in the proliferation assay was determined via linear regression, whereas significance of MMP-1 and Integrin α2 expression was measured by t test. The differences were considered statistically significant when p < 0.05. All the analyses were performed using Prism® 5 for Macintosh [GraphPad Software Inc., La Jolla, CA].
Proliferation of MCF-7
Expression of MMP-1
Expression of integrin α2
Major achievements have been made in breast reconstruction following mastectomy surgery. The standard of care to reconstruct the breast has focused on tissue expander/implants and the use of flaps . Although often very effective in restoring the contour of the breast, both procedures are not without complications. Donor site morbidity is a major issue in flap procedures . Capsule formation after prosthetic implants and radiotherapy-induced complications are still challenging [29, 30]. In general, autologous methods are favorable in terms of long-term stability of results. However, patient safety must have priority in choosing the method of reconstruction.
Fat grafting has become frequently used for breast reconstruction after mastectomy . Petit et al. concluded in a multicenter study that lipofilling of the breast is a safe procedure after most oncological breast surgeries . In contrast, Yu et al. demonstrated in an animal model, that co-injection of adipocytes-derived stem cells (ASCs) promote proliferation of tumor cells . Furthermore, several other studies described the effect of stromal cells on tumorigenesis in terms of cancer survival, proliferation, invasion, and migration . In this study, we report that lipoaspirates significantly increase proliferation of human MCF-7 breast cancer cells in vitro. It is well known that adipocytes contain a variety of tumor promoting factors, even in estrogen-negative cells, like adiponectin, leptin, collagen IV, and hepatocytes growth factor [35–38]. Therefore, not only ASCs enhance tumor growth but also adipocytes as contained in lipoaspirates may stimulate tumor growth. Tumor invasion is a hallmark of malignant tumors. The ability of tumor cells to degrade the ECM indicates the invasion potential of these cells and subsequently migration and metastasis [7, 39]. We detected a significant increase in MMP-1 expression in MCF-7 cells when co-cultured with lipoaspirates. In comparison, MMP-1 was not detectable in control groups (non-co-cultured). Interestingly, MMP-1 showed higher existence in hunger medium (1% FCS) than in saturated medium (10% FCS), which may suggest the higher tendency to invade the ECM under the former medium. Tumor metastasis to secondary sites demands cell motility as well as interactions between tumor cells and the microenvironment. As binding molecule, Integrin α2β1 has shown high expression in tumor cells isolated from secondary sites [40–43]. In our study, the expression of Integrin α2 in Western blot was significantly higher in lipoaspirates-co-cultured MCF-7 cells than the control groups. Riikonen et al. reported an association between Integrin α2β1 and regulation of MMP-1 expression . In their findings, the increase of Integrin α2 levels was positively associated with an elevation of MMP-1 expression. In our study, we could also demonstrate an increase in Integrin α2 levels accompanied with upregulated MMP-1 expression. However, this effect was differentially regulated with higher Integrin α2 levels resulting in only moderate increase of MMP-1 expression over controls. The exact role of different levels of Integrin α2 overexpression is still controversial [45–47].
Apart from lipofilling, DIEP flap is considered as the gold standard procedure to reconstruct the breast especially in Europe . DIEP flap contains fat cells in their regular texture and tissue composition. Our study demonstrates for the first time the impact of adipose tissue ‘en bloc’ as a small subunit of the DIEP flap on breast cancer cells. We have reported a significant increase in proliferation of DAF-co-cultured MCF-7 cells than non-co-cultured cells. Interestingly, it showed statistically no difference between the proliferation of MCF-7 cells co-cultured with DAF or lipoaspirates. Furthermore, the level of MMP-1 in MCF-7 cells was equally elevated by addition of DAF or lipoaspirates. MMP-1 demonstrates not only the invasive activity of cells through degradation of the ECM, but also has a crucial role in the process of metastasis through intercellular signaling . Moreover, the expression of Integrin α2 was significantly increased in DAF-co-cultured MCF-7 cells but with no difference to cells co-cultured with lipoaspirates. This indicates the stimulation of the carcinogenic growth and migration potential of MCF-7 cells by exposure to either forms of fat tissue. However, we cannot rule out that MCF-7 cells in co-culture with fat tissue may induce an increase of MMP-1 expression in the fat tissue itself. Gao and Bing reported that MMP-1 is expressed and secreted by preadipocytes and to a much lesser extent in mature adipocytes, but can be stimulated by macrophage-conditioned medium in both cells types .
Proliferation, invasion, and migration are all different pathological behaviors of cancer cells. Ultimately, DAF and lipoaspirates exhibit an equal enhancement of these behaviors on breast cancer cells (MCF-7). It is known that stromal vascular fraction and mature adipocytes share about 60% of their proteome . Therefore, we could understand the tumorigenic effect of DAF and lipoaspirates as well. Before identification of ASCs, obesity was linked to breast cancer in postmenopausal women. Both, the risk and the rate of mortality by breast cancer have been associated with obesity in several studies [51–55]. Over weight has been shown to affect the prognosis through enhancing the metastasis rate and resistance to drugs [56, 57]. Moreover, abdominal obesity and breast cancer were strongly linked in several studies [58, 59]. While ASCs are not the only player in stimulation of tumorigenic growth, the presence of adipocytes have also increased the carcinogenicity as contained in a flap or suspended in lipoaspirates.
Approximately 80–100% of breast cancer recurrences occur at the tumor bed in the first 3–5 years after initial treatment. Thus, local residing cancer cells and the elimination of recurrence risk will remain the main concerns in reconstructive surgery after mastectomy. Our study addresses the tumorigenic growth of human breast cancer cells by fat tissue transfer in vitro. Independent of harvesting procedure, fat tissue obviously bears the potency to enhance tumorigenic growth activity of cancer cells in vitro. Notably, autologous flaps have been applied without remarkable oncologic complications for many years in vivo. It remains to be investigated whether lipofilling triggers any oncologic diseases in healthy patients. Therefore it seems warranted to assess the cancer recurrence risks and the safety of reconstructive surgery in extended clinical studies in the future.
American Society of Plastic Surgeons
adipose-derived Stem cells
basic fibroblast growth factor
basement membrane extract
body mass index
dissected abdominal fat
- DIEP flap:
deep inferior epigastric artery perforator flap
fetal calf serum
insulin-like growth factor 1
- msTRAM flap:
muscle-sparing Transvers Rectus Abdominis Myocutaneous flap
non-essential amino acids
platelet-derived growth factor
- RPMI 1640 medium:
Roswell Park Memorial Institute medium
standard error of mean
vascular endothelial growth factor
FA drafted the manuscript, collected the data, conducted the culture, AlmarBlue® and ELISA in vitro procedures and participated in statistical analysis. HOR participated in the design of the study and drafting the manuscript. JPS participated in conduction of Western blot and statistical analysis. ZA helped in the organization of materials and assisted during surgery. NP performed all surgical procedures, funded this study and helped to draft the manuscript. All authors read and approved the final manuscript.
All the Authors thank Mrs. Andrea Dresen for her assistance in the laboratory work, and the Department of Medical Statistics at RWTH University (Chairman: Prof. Ralf-Dieter Hilgers) for guidance in statistical analysis. Additionally, Our thanks to Daniel Heinrichs from Institute of Biochemistry and Molecular Cell Biology at RWTH University (Chairman: Prof. Jürgen Bernhagen) for his help in Western blot analysis. Finally, we acknowledge the American Manuscript Editors for their extensive editing service of this manuscript.
The authors declare that they have no competing interests.
Availability of data and materials
The datasets of the current study are available from the corresponding author on reasonable request.
The protocol and the use of human materials were approved by the ethics committee of the Faculty of Medicine at RWTH University in Aachen, Germany (Name in German: Ethik-Kommission des Universitätsklinikums Aachen, Votum Number: EK206/13). The experiments were carried out in compliance with Declaration of Helsinki in its current form.
The authors received no financial support related to the development of this article.
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