Dissecting the association between breast cancer and scar conditions and fibrosis of skin : a bidirectional Mendelian randomization study

doi:10.21203/rs.3.rs-4885966/v1

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Dissecting the association between breast cancer and scar conditions and fibrosis of skin : a bidirectional Mendelian randomization study

https://doi.org/10.21203/rs.3.rs-4885966/v1

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Background

Scar hyperplasia and skin fibrosis following breast cancer operation has long been recognized as one of the major effects affecting patients' quality of life. However, there is currently a lack of direct evidence examining the impact of breast cancer on scar conditions and fibrosis of skin.

Methods

In this study, a two-way, two-sample Mendelian randomisation (MR) approach utilising pooled data from a genome-wide association study (GWAS) we employed to investigate the potential causal relationship between breast cancer (BC) and scar conditions and fibrosis of skin.In forward MR, it was postulated that BC was the exposure factor, whereas in reverse MR, scar conditions and fibrosis of skin were posited as the exposure factors. To enhance the reliability of the results, two databases (finna-a-L12_SCARCONDITIONS; ukb-b-11403 ) were employed to examine these factors.In order to explore the potential relationship between BC and scar conditions and fibrosis of skin, various analytical techniques were utilised, including random effects inverse variance weighted (IVW) and MR-Egger analyses.Furthermore, sensitivity analyses and assessments of heterogeneity and multiplicity were conducted to enhance the reliability of the results.

Results

The MR analysis indicates that BC is associated with an elevated risk of scar conditions and fibrosis of skin(OR = 1.310, 95%CI = 1.052–1.630, p = 0.015 ) and(OR = 1.00047, 95%CI = 1.000016–1.000928, p = 0.042 ) .In contrast, the inverse MR analysis did not identify scar conditions and fibrosis of skin as a potential factor influencing BC risk.Furthermore, sensitivity analyses of these results demonstrated the absence of evidence for heterogeneity or pleiotropy.

Conclusion

This study showed that a positive causal relationship exists between BC and scar conditions and fibrosis of skin in European populations. This study also offers a novel perspective on the mechanism study of postoperative scar formation in breast cancer patients, and provides a novel basis for clinical assessment of patients' prognosis based on the status of surgical scarring in BC and the degree of dermal fibrosis.

Breast cancer

scar conditions and fibrosis of skin

mendelian randomization

tumour inflammatory environment

The formation of scar tissue is an inevitable consequence of the wound repair process. A number of factors, including excessive collagen deposition and increased fibrosis, can contribute to the development of an unfavourable scarring outcome,It is estimated that 40–70% of post-surgical wounds are classified as hyperplastic scarring (HTS), a form of undesirable scarring that manifests as abnormal tissue proliferation during the healing process, characterised by fibrosis of the skin[1].The development and progression of scarring is influenced by a complex interplay of factors, including local factors, systemic factors, genetic predisposition, and lifestyle.Adverse scarring states may manifest with contractures of the skin, pruritus, and pain. These symptoms may result in a disruption of the cosmetic appearance of the affected area, functional impairment, and psychological distress.A questionnaire survey of 11,000 individuals from across the globe revealed that scarring has a profound impact on the quality of life of those affected, leading to adverse psychosocial effects[2].The current range of scar treatments encompasses moisturisation/compression, surgical procedures, laser therapy and laser-assisted drug delivery[3].However, due to the inherent variability among individuals, untargeted therapies may result in adverse reactions, including skin spasm and atrophy, capillary dilatation, pigmentation, and ulceration. These reactions can further exacerbate the physiological and psychological burdens experienced by patients[4, 5].It is thus imperative to investigate the factors that contribute to scarring and the potential for scarring status and dermal fibrosis, as well as the potential consequences that can result from adverse scar formation.

Pathologist Harold Dvorak suggests that "tumor: wounds that do not heal"[6].The extant literature indicates that neoplasm of epithelial origin exhibit parallels with the processes of wound healing at the cellular and molecular levels[7, 8].As early as 2004, Chang et al. conducted a study on gene expression in fibroblasts, which revealed that the expression of malignancy marker genes was aberrant during the wound healing process[9].The clinical findings indicate that approximately 60% of patients who undergo bilateral breast resurfacing or median sternotomy procedures develop HTS in the postoperative period[10].A number of dermatological complications may arise in the initial stages of BC and in the period following surgery and radiotherapy. These include scarring and fibrosis, and malignant or benign lesions may develop in the scars left by BC[11, 12].Furthermore, the presence of radial scarring was found to be significantly and positively correlated with an elevated risk of developing BC[13].Additionally, surgical scarring resulting from other surgical procedures, such as radical mastectomy for BC, can precipitate discomfort, restricted mobility, and psychological distress. The severity of surgical scarring is significantly associated with patients’quality of life[14].The observed correlation between the occurrence of BC and recovery from surgery in relation to scar conditions and fibrosis of skin indicates a necessity for further research into the potential causal relationships between BC, scar conditions and fibrosis of skin.

The recently developed Mendelian randomization (MR) method is employed to ascertain the causal relationship between risk factors or biomarkers and disease. This is achieved by utilizing genetic variation as an instrumental variable[15].The fundamental premise of the method of randomisation MR is to utilise random assortment of genetic material during meiosis for the purpose of emulating randomised controlled trials and subsequently deriving conclusions regarding the relationship between cause and effect.MR offers a more robust methodology for establishing causality than traditional observational studies.The aforementioned advantage arises from the fact that genetic variation is established at the time of conception, which serves to minimise the potential for confounding or reverse causation.

This study first performed a two-way two-sample MR was employed to examine the relationship between BC and scar conditions and fibrosis of skin. Secondly, we retrieved BC pooled data from the Genome-Wide Association Study (GWAS) database and extracted single-nucleotide polymorphisms (SNPs), thereby providing a potential foundation for clinically evaluating the prognosis of patients based on their surgical scarring status and the degree of skin fibrosis in the context of BC.

2.1 Research design and ethical statements

This study employed GWAS summary statistics to ascertain the causal relationship between BC (exposure) and scar conditions and fibrosis of skin (outcome) through two-way two-sample MR.The MR design is predicated on three fundamental assumptions. Firstly, it is essential to demonstrate that genetic variants are reliably associated with exposure. Secondly, there should be no confounding factors associated with the genetic variants that could influence the relationship between exposure and outcome. Ultimately, the association between these genetic variants and the outcome must be solely attributable to exposure[16].(Fig. 1)

The data employed in our analyses were derived exclusively from publicly accessible GWAS data sets, and no new study populations were included. Consequently, no ethical approval was sought.

2.2 Data sources

The data pertaining to BC were obtained from the IEU Open GWAS public database (ebi-a-GCST90018799)[17].The dataset comprises a sample size of 257,730 European populations and 24,133,259 SNPs.

GWAS summary data on scar conditions and fibrosis of skin were obtained from the FinnGen consortium (finna-a-L12_SCARCONDITIONS).The dataset comprises a sample size of 207,982 European populations and 16,380,440 SNPs.Furthermore, an additional pooled database of scar conditions and fibrosis of skin was employed to enhance the dependability of the findings. This database was derived from the UK Biobank (ukb-b-11403).The dataset comprises a sample size of 463,010 European populations and 9,851,867 SNPs.

The GWAS data employed in this study are accessible via the IEU Open GWAS project.

2.3 SNPs selection

SNPs that are closely associated with BC, scar conditions, and fibrosis of the skin were selected to satisfy the prerequisites for MR, based on a genome-wide significance threshold of P < 5 × 10^− 8 [18].The effect of chain imbalance was subsequently addressed via a chain imbalance analysis, whereby SNPs exhibiting chain imbalance distances exceeding 10,000 kb and r² < 0.001 were subjected to clustering[19].Furthermore, instrumental variables (IV) for genome-wide associations with a significance level of 5×10^− 8 were also excluded.Subsequently, the echo SNP was excluded following the implementation of the coordination process. The strength of IV was evaluated through the application of the F-statistic.

2.4 Statistical analysis

This study employed the inverse variance weighting (IVW) method with MR-Egger regression to ascertain the potential causal relationship between BC and scarring status and dermal fibrosis.These valuations were converted into ratios (OR) in order to elucidate potential causal relationships through the use of OR values.The IVW approach synthesises the individual variant exposures and variant outcome associations in order to obtain overall estimates of causal effects.To ascertain whether horizontal multifunctionality was present, sensitivity analyses were conducted utilising the MR-Egger and MR-PRESSO tests[20].All analyses were conducted utilizing the R software (version 4.4.0) with the "TwoSampleMR (version 0.6.4)" package.

Furthermore, reverse analysis was employed to evaluate the influence of scar conditions and fibrosis of skin on the development of BC. The objective of this analytical instrument was to investigate the possibility of reverse causality and to ascertain whether there was a causal relationship between the exposure factors and the outcome[21].This approach is less common than the standard MR, but it offers greater insight into the potential causal relationship between outcome and exposure, particularly when the causal relationship is unclear. It also provides more reliable evidence.

3.1 Causal effects of breast cancer on scar conditions and fibrosis of skin

Applying the GWAS significance threshold of P < 5 × 10^− 8 after excluding concatenated unbalanced SNPs,The BC-associated SNPs were collected as instrumental variables through which the causal relationship with scar conditions and fibrosis of skin was investigated.(Supplementary Table S1-2)MR analysis using a random effects IVW model showed a suggestive positive causal relationship between BC, scar conditions and increased risk of dermatofibrosis.(Fig. 2,3)Using the database of the FinnGen consortium, the causal relationships analysed were༈OR = 1.310, 95%CI = 1.052–1.630, p = 0.015);The causal relationships analysed with the UKB database are༈OR = 1.00047, 95%CI = 1.000016–1.000928, p = 0.042), as detailed in Supplementary Table S3.

3.2 Reverse MR analysis

To further elucidate the causal association between BC and scar conditions and fibrosis of skin, we conducted a reverse MR analysis, utilizing scar conditions and fibrosis of skin as exposures to validate the outcomes of BC.Among these, SNPs closely associated with BC, scar conditions and fibrosis of skin were selected based on a genome-wide significance threshold of P < 5 × 10^− 6 to meet the requirements for MR.The inverse MR analysis did not yield any evidence suggesting a potential causal relationship between scarring status and dermal fibrosis and BC. This was indicated by a p-value of less than 0.05 by the IVW method.( Supplementary Table S5-7)The findings of the study indicated that there was no reverse causality between BC and scar conditions and fibrosis of skin.

3.3 Sensitivity analysis

In order to reinforce the causal relationship between BC and scar conditions and fibrosis of skin, a series of sensitivity analyses were conducted.The presence of heterogeneity was evaluated through the application of Q-testing to the IVW method and MR-Egger, while the potential for horizontal multiplicity was assessed through the utilisation of MR-Egger intercept tests, leave-one-out analyses and funnel plots.The IVW methods and the MR-Egger Q-test, with a p-value greater than 0.05, indicate the presence of significant heterogeneity. Conversely, a p-value greater than 0.05 for the MR-Egger intercept test suggests the absence of horizontal multivalency.(Supplementary Table S4)Leave-one-out analysis and funnel plots.(Fig. 4,5)The results of these sensitivity analyses provide evidence of the reliability and stability of the findings of this study.

The formation of scars is an inevitable consequence of the skin wound healing process and represents a more common manifestation of dermal fibrosis. Both scarring and dermatofibrosis are fibroproliferative disorders of the reticular dermis of the skin. They are characterized by the abnormal deposition of collagen, angiogenesis and infiltration of inflammatory factors. Concurrently, it is evident that there is a considerable degree of variability in the endpoints of wound recovery across different populations. Various factors, including age, smoking, alcohol consumption, nutritional status, and genetics, have been demonstrated to exert influences on the extent of scarring and the degree of dermal fibrosis. At the cellular level, skin fibroblasts are of significant importance in the processes of skin scarring and fibrosis. Furthermore, the immune system is intimately associated with the pathogenesis of dermal fibrosis and scarring. This is evidenced by the pivotal role played by interleukin (IL)-4 and IL-13, along with Th2-mediated type II immune responses, in this process[22]. It has been demonstrated that fibroblasts in tumor tissues can be hijacked by cancer cells to become cancer-associated fibroblasts(CAFs). These cells secrete an array of factors, including collagen and transforming growth factor, which collectively promote tumor cell proliferation, migration, immune tolerance and chemotherapy resistance. Additionally, IL-4 and IL-13 have been identified as key contributors to tumorigenesis[23]. To further elucidate the potential association between BC and scar conditions and fibrosis of skin, we conducted a two-way two-sample bidirectional MR analysis, which revealed a positive correlation between these three variables.

Cancers are primarily a pathological process of uncontrolled cell proliferation, regulated by the organism in a complex and multifactorial manner. During this process, the whole organism is affected by a series of reactions generated by the cancer, which induce inflammatory and immune responses, excessive nutrient depletion and metabolic disorders[24]. These factors, in turn, exert an influence on scar status and the advent of dermal fibrosis.

During the development of BC, there is an increase in the systemic inflammatory response, which in turn leads to elevated levels of other pro-inflammatory factors, including tumor necrosis factor (TNF)-α, transforming growth factor-β (TGF-β), interferon γ (INF-γ), IL-8, IL-10 and others[25–27].The persistence of this chronic inflammatory milieu results in the amplification of inflammatory mediators in a cascading manner. In particular, interactions between adipocytes and macrophages result in a significant increase in the production of pro-inflammatory factors by macrophages. Among these factors, TNF-α, IL-1β and TNF-α can activate stimulatory transcription factor nuclear factor-κB (NF-κB). This process is involved in the inhibition of apoptosis and the initiation of the expression of IL-1β, monocyte chemokine-1 (MCP-1), TGF-β, and macrophage migration inhibitory factor (MIF), as well as other inflammatory factors[28, 29].Consequently, the levels of these inflammatory factors influence the formation of scars and the progression of fibrosis. For instance, elevated levels of IL-1β stimulate the high expression of IL-6, which in turn stimulates fibroblast proliferation and excessive collagen deposition through the activation of the trans-signal STAT3 pathway. These signal transduction ultimately promote the development of proliferative scarring[30]. It was demonstrated that MCP-1 expression levels were markedly elevated in the presence of diverse dermal fibrosis conditions. In comparison to wild-type mice, dermal fibrosis was markedly diminished at the site of bleomycin injection in MCP-1 knockout mice. Additionally, subcutaneous fat was partially preserved, and mononuclear cell infiltration was reduced at the lesion skin[31].TGF-β is also inextricably linked to the processes of scarring and fibrosis, and plays a central role throughout the stages of these processes. A considerable number of studies have employed TGF-β blockade as a therapeutic instrument for scar repair and the inhibition of tissue fibrosis[32, 33]. MIF, a principal regulator of estrogen (ER), also exerts a pivotal influence on fibrotic diseases and wound healing. Proteomics investigations have revealed markedly elevated MIF levels in hyperplastic scar tissues relative to normal skin, indicating a close correlation between MIF and scarring and dermal fibrosis[34, 35].Additionally, approximately 20% of individuals diagnosed with BC also present with metabolic syndrome (MS), the progression of which is negatively correlated with patient prognosis[36].The study by Kridin K et al. demonstrated that acne keloid naevus (AKN) was also significantly correlated with MS, indicating that BC-induced MS may influence the postoperative scar status and dermal fibrosis[37]. In conclusion, BC may impact the postoperative skin scar conditions and the process of skin fibrosis through the mechanisms of inflammation, immune response, and metabolism.

In this study, MR analysis was employed to ascertain the causal relationship between BC and scar conditions and fibrosis of skin. This approach helps to eliminate the effects of confounding variables and minimize the possibility of reverse causation, thus enhancing the capacity to ascertain causality. However, it should be noted that the study is not without limitations. It is important to note that the majority of the data presented in the GWAS database are sourced from European populations. Given the inherent differences in the genetic background of these populations, the applicability of these findings to other ethnic groups requires further evaluation. Secondly, due to the influence of lifetime genetic exposure, MR effect estimates may not accurately reflect the temporal dynamics of the underlying effect. The causality derived in this study requires further validation through additional clinical investigation.

This study indicated that a positive causal relationship existed between BC and scar conditions and fibrosis of skin. Through genetic evidence and additional supportive association analyses, this study offers new avenues for the mechanism study of postoperative scar formation in breast cancer patients, and also provides a novel basis for clinical assessment of patients' prognosis based on the status of surgical scarring in BC and the degree of dermal fibrosis.

Conflict of interest statement

The authors have declared that no competing interests exist.

Funding information

This work is supported by the National Natural Science Foundation of China (81772833) and Hubei Provincial Natural Science Foundation of China (2023AFB143),Yichang Science and Technology Project (A23-1-073).

Author Contribution

J.C., R.Q, and C.C. wrote the main manuscript text and X.L. Participated in the conceptualization of the manuscript and the review of data. All authors reviewed the manuscript.

Acknowledgement

We express our sincere appreciation to the three large GWAS databases, UK Biobank,European Bioinformatics Institute and the FinnGen consortium, for generously sharing research results data. We are also deeply grateful to all participants and investigators involved in the FinnGen consortium,European Bioinformatics Institute and UK Biobank studies.

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No competing interests reported.

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Dissecting the association between breast cancer and scar conditions and fibrosis of skin : a bidirectional Mendelian randomization study

Status:

Version 1

Abstract

Background

Methods

Results

Conclusion

Figures

1.Introduction

2. Materials and methods

2.1 Research design and ethical statements

2.2 Data sources

2.3 SNPs selection

2.4 Statistical analysis

3. Result

3.1 Causal effects of breast cancer on scar conditions and fibrosis of skin

3.2 Reverse MR analysis

3.3 Sensitivity analysis

4. Discussion

5. Conclusion

Declarations

Conflict of interest statement

Funding information

Author Contribution

Acknowledgement

References

Additional Declarations

Supplementary Files

Status:

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