Spatial microenvironment heterogeneity in therapy-naïve lung cancer: A concept with more attention needed

To the editor, Tumor heterogeneity has gradually been regarded as an essential concept reflecting tumor biological behavior, influencing treatment selection and therapy response [[1]Zugazagoitia J. Gupta S. Liu Y. et al.Biomarkers associated with beneficial PD-1 checkpoint blockade in non-small cell lung cancer (NSCLC) identified using high-plex digital spatial profiling.Clin. Cancer Res. 2020; 26: 4360-4368Crossref PubMed Scopus (59) Google Scholar]. For decades, less was looked into lung cancer's spatial tumor microenvironment (TME). In the recent issue (Volume 180, June 2023), we read with interest a cross-sectional study by H. Goldschmid et al. [[2]Goldschmid H. Kluck K. Ball M. et al.Spatial profiling of the microenvironment reveals low intratumoral heterogeneity and STK11-associated immune evasion in therapy-naïve lung adenocarcinomas.Lung Cancer. 2023; 180107212Abstract Full Text Full Text PDF PubMed Scopus (1) Google Scholar] that revealed a lesser intratumoral TME heterogeneity than the intertumoral in therapy-naïve lung adenocarcinoma regarding immune cell signatures. The result was clinically significant in the context of predictive biomarkers assessment based on small biopsies before neoadjuvant immunochemotherapy [[3]Forde P.M. Spicer J. Lu S. et al.Neoadjuvant nivolumab plus chemotherapy in resectable lung cancer.N. Engl. J. Med. 2022; 386: 1973-1985Crossref PubMed Scopus (523) Google Scholar]. The finding indicates limited tissue might suffice to infer the overall tumor landscape. However, some points are worth noting in the study design (Fig. 1a), and here we also profiled a case of multiple lung cancers for relevant discussion on this topic. First, It is unclear what specific regions were sampled upon the lesion. Multiregional site sampling across the tumor for each patient in the study [[2]Goldschmid H. Kluck K. Ball M. et al.Spatial profiling of the microenvironment reveals low intratumoral heterogeneity and STK11-associated immune evasion in therapy-naïve lung adenocarcinomas.Lung Cancer. 2023; 180107212Abstract Full Text Full Text PDF PubMed Scopus (1) Google Scholar] showed most of the analyzed cases (14/19, 74%) possess a homogenous spatial immune cell profile (consistently low or high immune cell infiltrates). However, a single tumor consisted of different areas including tumor center, tumor stroma and tumor margin, mirroring distinct contexture (Fig. 1b). For example, previous studies showed a marked predominance of M2 macrophage at the tumor margin, whose distribution serves as a prognostic factor for lung carcinoma [[4]Zheng X. Weigert A. Reu S. et al.Spatial density and distribution of tumor-associated macrophages predict survival in non-small cell lung carcinoma.Cancer Res. 2020; 80: 4414-4425Crossref PubMed Scopus (84) Google Scholar]. The tumor stroma was characterized by a comprehensive catalog of fibroblasts and endothelial cells that correlate with immune cell activity [[5]Lambrechts D. Wauters E. Boeckx B. et al.Phenotype molding of stromal cells in the lung tumor microenvironment.Nat. Med. 2018; 24: 1277-1289Crossref PubMed Scopus (845) Google Scholar]. In our case, transcriptomic analysis based on the digital spatial profiling (DSP) technique revealed a well-distributed low immune infiltration in the tumor center with a relatively large heterogeneity for the distribution of immune cells in the non-tumor areas (Fig. 1c). Therefore, different area sampling would result in a distinct intratumoral heterogeneity, which may potentially be a confounder in the study [[2]Goldschmid H. Kluck K. Ball M. et al.Spatial profiling of the microenvironment reveals low intratumoral heterogeneity and STK11-associated immune evasion in therapy-naïve lung adenocarcinomas.Lung Cancer. 2023; 180107212Abstract Full Text Full Text PDF PubMed Scopus (1) Google Scholar]. Second, we believe that it would be better to include heterogeneity of the common targeted gene alterations as one of the main measures in the study. Neoadjuvant targeted therapy has been popularized in clinical practice for locally advanced lung cancer in significantly improving progression-free survival [[6]Zhong W.Z. Chen K.N. Chen C. et al.Erlotinib versus gemcitabine plus cisplatin as neoadjuvant treatment of stage IIIA-N2 EGFR-mutant non-small-cell lung cancer (EMERGING-CTONG 1103): A randomized phase II study.J. Clin. Oncol. 2019; 37: 2235-2245Crossref PubMed Scopus (154) Google Scholar]. Genetic testing for unresectable lung cancer is always based on pathological specimens from a small biopsy, and the results were supposed to affect subsequent regimen selection. Our case showed a relatively homogeneous abundance of mutated genes in the tumor center except for a few remaining large heterogeneity (Fig. 1d). Understanding different expression abundance of intratumoral targeted gene has practical significance. Third, natural history of lung cancer progress may results in a dynamic varying intratumoral heterogeneity since the de novo tumor evolve from monoclonal to polyclonal features with different subtypes of cells [[7]Turajlic S. Sottoriva A. Graham T. et al.Resolving genetic heterogeneity in cancer.Nat. Rev. Genet. 2019; 20: 404-416Crossref PubMed Scopus (336) Google Scholar]. The study [[2]Goldschmid H. Kluck K. Ball M. et al.Spatial profiling of the microenvironment reveals low intratumoral heterogeneity and STK11-associated immune evasion in therapy-naïve lung adenocarcinomas.Lung Cancer. 2023; 180107212Abstract Full Text Full Text PDF PubMed Scopus (1) Google Scholar] included 19 untreated lung adenocarcinomas covering pathological stage IA to IIIB, while it is unclear what the impact of the advanced stage was on the intratumoral heterogeneity relative to the early stage. Temporal patterns resulting from disease upstage may lead to greater disparity in tumor heterogeneity. Furthermore, it would be better to include an association analysis of the TME heterogeneity and radiological morphology or histological subtypes. Assumption hold that these clinical features may be indicators for inferring microenvironment heterogeneity. Finally, in the study [[2]Goldschmid H. Kluck K. Ball M. et al.Spatial profiling of the microenvironment reveals low intratumoral heterogeneity and STK11-associated immune evasion in therapy-naïve lung adenocarcinomas.Lung Cancer. 2023; 180107212Abstract Full Text Full Text PDF PubMed Scopus (1) Google Scholar] the finding that higher intertumoral heterogeneity between different individuals seems obvious, as we know patients have different epigenetic features [[8]Tavernari D. Battistello E. Dheilly E. et al.Nongenetic evolution drives lung adenocarcinoma spatial heterogeneity and progression.Cancer Discov. 2021; 11: 1490-1507Crossref PubMed Scopus (47) Google Scholar]. Spatial profiling of multiple lung cancers of the same patient may be of more interest than that of a single lesion in the design setting. Understanding TME heterogeneity in multiple primary lung cancers may provide insights into the distinctive treatment efficacy. Case studies revealed that neoadjuvant immunochemotherapy yielded a better response for radiological solid lesions than the subsolid ones [[9]Zhang C. Yin K. Liu S.Y. et al.Multiomics analysis reveals a distinct response mechanism in multiple primary lung adenocarcinoma after neoadjuvant immunotherapy.J. Immunother. Cancer. 2021; 9Crossref Scopus (19) Google Scholar]. Distinct patterns could be seen in different radiologic and pathologic lesions in our case (Fig. 1cd). We believe the investigation of heterogeneity for multiple lung cancers would be more meaningful. TME heterogeneity in therapy-naïve lung cancer is a new topic that has not been thoroughly studied. The work for Goldschmid et al. [[2]Goldschmid H. Kluck K. Ball M. et al.Spatial profiling of the microenvironment reveals low intratumoral heterogeneity and STK11-associated immune evasion in therapy-naïve lung adenocarcinomas.Lung Cancer. 2023; 180107212Abstract Full Text Full Text PDF PubMed Scopus (1) Google Scholar] was innovative and provided insights into the understanding of the initial tumor state at therapy, though some factors were not fully considered, perhaps due to the cost of testing and sample size. Intratumoral heterogeneity is closely related to carcinogenesis, biological behavior, treatment resistance, and prognosis. At the same time, it also is affected by some clinical factors mentioned above. Future studies would focus on this relevant topic to determine what role the untreated TME plays. No sources of funding were used to assist in the preparation of this letter.