Presence of Chronic Inflammatory Signatures in Breast Tissue of Textured Implant Patients
development of breast implant-associated anaplastic large cell lymphoma (BIA-ALCL), our
understanding of the etiologic mechanisms in BIA-ALCL still remains largely vague. Literature
focuses on two possible mechanisms of tumorigenesis: mechanical inflammation and bacterial
infection. Both theories rely on the inflammatory pathways associated with damage-associated
molecular patterns (DAMPs) and pathogen-associated molecular patterns (PAMPs). DAMPs
have been implicated in many kinds of cancer, including breast cancer. We hypothesize that
textured implants initiate one or multiple inflammatory pathways, either via DAMPs and/or
PAMPs, which results in enhanced inflammation and a pro-tumor environment. To investigate
this, we measured gene expression of tissue collected from women with smooth and textured
breast implants to compare inflammation and immune-related pathways between the two cohorts.
Methods/Technique: Breast tissue was collected at the time of surgery from patients undergoing
first implant exchange or removal surgery (n=25). This tissue was processed for total RNA. Bulk
RNA sequencing analysis was performed on 9 patients: 3 with textured implants prior to surgery
(textured cohort), and 6 with smooth implants prior to surgery (smooth cohort). Pathway and cell
marker association analysis on bulk RNA-seq gene output was performed using Gene Ontology
Enrichment Analysis and Gene Set Enrichment Analysis (GSEA) software. Confirmatory
quantitative real time PCR (qRT-PCR) was performed on selected genes of interest for all 25
patients: 6 patients in the textured cohort and 19 patients in the smooth cohort. Genes of interest
included those related to elevated pro-tumor inflammation pathways seen in bulk RNA-seq
analysis. Inflammation pathway target gene expression levels were normalized to GAPDH and
expressed as fold change (FC) relative to the smooth implant cohort. Groups were compared
with Welch’s unpaired t-tests using Graphpad Prism v9.1.2.
Results/Complications: Analysis of transcriptome data from bulk RNA sequencing showed that there was a
total of 263 genes differentially expressed (adjusted P<0.05) between the two cohorts. The most
significantly elevated pathways in textured versus smooth cohorts included positive regulation of
IL-1β production (a pro-inflammatory cytokine), pattern recognition receptor signaling,
regulation of response to biotic stimulus, regulation of defense responses, general inflammatory
response, and general immune system response. More specific differences included neutrophil
degranulation, regulation of phagocytosis, and both innate and adaptive immune systems and
cells. Elevated expression of markers associated with bone marrow neutrophils, classical
monocytes, nonclassical monocytes, Kupffer cells, and proliferating macrophages were also
found in textured cohort breast tissue. Confirmatory qRT-PCR was performed on significant
DAMP and PAMP-associated inflammation pathway genes found to be elevated in bulk RNA-
seq including inflammasomes NLPR12 and NLCR4, pattern recognition receptor TLR4, and
inflammatory cytokine IL-1β with converting enzyme CASP1. While all genes were elevated in
the textured group (NLCR4 FC=2.05, TLR4 FC=2.06, IL-1β FC=4.40, CASP1 FC=1.25), only
NLPR12 was significantly elevated (FC=4.6, SD=2.26, P=0.012).
Conclusion: Even with a small sample size, 263 genes were found to be differentially expressed
between the two cohorts. These included immune and inflammatory related genes. Some genes
found to be elevated in textured patients are involved in DAMP- and PAMP-mediated
inflammation pathways and are known to be associated with pro-tumor inflammation, including
the IL-1β pathway and the NLPR12 inflammasome. Elevated levels of NLPR12 could
potentially be involved in the formation of BIA-ALCL. Further analysis also showed
upregulation of many pathways associated with inflammation and immunity in response to
pathogens or damage.