Analysis Of Correlation Between Spread Through Air Spaces(STAS) And Biological Behavior Of Invasive Adenocarcinoma Of The Lung

BackgroundAccording to the global cancer statistics in 2020,it is reported that lung cancer is the tumor with the highest mortality in the world^[1,2],and the incidence of lung adenocarcinoma is increasing.Although the early detection rate of lung cancer has been greatly improved through imaging screening,there is still a high proportion of lung adenocarcinoma patients with recurrence and metastasis after operation^[3].The concept of tumor spread through air spaces was explicitied and formally specified in lung carcinoma classification of World Health Organization（WHO）in the year of2015.The in-depth exploration of the phenomenon in tumor spread through air spaces plays an important role in predicting the risk of recurrence of lung adenocarcinoma and studies of the mechanism of invasion and metastasis of lung adenocarcinoma.ObjectiveTo investigate the effect and machanisms of regulation of the STAS to biological behaviours in lung adenocarcinoma,we have analysied the correlation of clinicopathological factors and molecular characteristion between the tumor spread through air spaces（STAS）and non-mucous invasive adenocarcinoma of lung（hereinafter referred to as the lung adenocarcinoma）.And the difference of gene mutation between tumor cell clusters in STAS and the main tumor was preliminarily explored.MethodsA total of 694 patients with non-mucinous invasive adenocarcinoma of lung diagnosed by clinicopathology from the First Affiliated Hospital of Guangzhou Medical University from July 2019 to March 2021 were reviewed to analyze the relationship between STAS and clinicopathological factors.The state of protein expression of Anaplastic lymphoma kinase（ALK）and c-ROS sarcoma carcinogenic factor receptor（ROS1）was detected by immunohistochemical method.The condition of genetic mutation of Epidermal growth factor receptor（EGFR）was detected with fluorescent quantitative polymerase chain reaction（PCR）technique.Using whole-exome sequencing（WES）to locate the mutant genes of tumor cell clusters in STAS and main tumor.Analyze the tumor mutation burden（TMB）and the tumor neoantigen burden（TNB）of the tumor cells in STAS and main tumor.ResultsA total of 344 STAS positive cases and 350 STAS negative cases were collected.By univariate analysis,STAS positivity was statistically associated with tumor maximum diameter（P<0.001）,pleural invasion（P<0.001）,lymphovascular invasion（P<0.001）,nerve invasion（P=0.013）,lymph node metastasis（P<0.001）,pathological stage（P<0.001）and histological type（P<0.001）.There was no significant correlation between STAS and sex（P=0.258）,age（P=0.360）,the mutation of EGFR（P=0.222）or the protein expression of ROS1（P=0.956）.Multivariate analysis showed that STAS positive was significantly correlated with pleural invasion（P<0.001）,vascular invasion（P<0.001）and ALK protein expression（P=0.001）.There was a statistical correlation between STAS and the proportion of micropapillary components,and there was a positive correlation（P<0.001）.The results of comprehensive gene analysis showed that TP53,DSPP,EGFR,HERC2,LAMA2,TTN,TUBB4A,TPI1 had differences in mutation sites between the tumor cell clusters in STAS and main tumor.Among them,partial mutations of TP53and TUBB4A only occurred in the main tumor,and partial mutations of TTN and TPI1genes only occurred in STAS tumor cell clusters.TMB and TNB levels were different between the tumor cell clusters in STAS and main tumor.ConclusionSTAS positivity was associated with the malignant phenotype of lung adenocarcinoma.The tumor cell clusters in STAS had a distinct genoma profile from the main tumor,suggesting that STAS tumor cell clusters might have more protected for immune escape.