Multi-regional sequencing reveals clonal and polyclonal seeding from primary tumor to metastases in advanced gastric cancer

Development of a molecular barcode detection system for pancreaticobiliary malignancies and comparison with next-generation sequencing

BACKGROUND

Obtaining sufficient tumor tissue for genomic profiling is challenging in pancreaticobiliary cancer (PBCA). We determined the utility of molecular barcoding (MB) of liquid biopsies (bile, duodenal fluid, and plasma) for highly sensitive genomic diagnosis and detection of druggable mutations for PBCA.

METHODS

Two in-house panels of 60 genes (non-MB panel) and 21 genes using MB (MB panel) were used for the genomic analysis of 112 DNA samples from 20 PBCA patients. We measured the yield of DNA and compared the genomic profiles of liquid samples obtained using the non-MB panel and the MB panel. The utility of the panels in detecting druggable mutations was investigated.

RESULTS

A significantly greater amount of DNA was obtained from bile supernatants and precipitates compared to tumor samples (P < 0.001 and P = 0.001, respectively). The number of mutations per patient was significantly higher using the MB panel than using the non-MB panel (2.8 vs. 1.3, P = 0.002). Tumor-derived mutations were detected more frequently using the MB panel than the non-MB panel (P = 0.023). Five drug-matched mutations were detected in liquid samples.

CONCLUSIONS

Liquid biopsy with MB may have utility in providing genomic information for the prognosis of patients with PBCA.

Polymorphism rs1057147 located in mesothelin gene predicts lymph node metastasis in patients with gastric cancer

Lymph node metastasis, a crucial factor in the spread of gastric cancer (GC), is strongly associated with a negative prognosis for patients. This study aimed to investigate the association of the mesothelin (MSLN) gene polymorphisms (rs3764247, rs3764246, rs12597489, rs1057147, and rs3765319) with the risk of lymph node metastasis of GC patients in a Chinese Han population. The PCR-LDR genotyping was used to detect the genotypes of MSLN polymorphisms in GC patients with lymph node metastasis (n = 610) or without (n = 356). Our research indicates that certain genetic markers, specifically rs3764247, rs3764246, rs12597489, and rs3765319, do not appear to be linked with an increased risk of lymph node metastasis in GC. However, we did observe that patients with the rs1057147 GA genotype exhibited a higher likelihood of lymph node metastasis in GC when compared to those with the GG genotype (OR = 1.33, 95% CI = 1.01 - 1.76, P = 0.045). Patients with rs1057147 GA + AA genotype were found to have a higher likelihood of lymph node involvement (OR = 1.35, 95% CI = 1.03 - 1.77, P = 0.029) when compared to those with GG genotype in the dominant model. The allelic model revealed that the A allele of rs1057147 exhibited a stronger correlation with lymph node metastasis compared to the G allele (OR = 1.28, 95% CI = 1.02 - 1.60, P = 0.031). In addition, we found that rs1057147 polymorphism revealed a poor prognosis for GC patients with lymph node metastasis. Further stratified analysis revealed that the prognostic effect of rs1057147 was more pronounced in patients with GC who had lymph node metastasis and had a tumor size of 4 cm or greater, as well as more than 2 lymph node metastases. Bioinformatics studies showed that the binding mode of miR-3144-5p or miR-3619-3p to MSLN was altered by the mutation of rs1057147. Our study confirmed the important role of MSLN rs1057147 polymorphism locus in GC lymph node metastases and suggested a potential prognostic factor during GC progression. KEY POINTS: • Rs1057147 GA genotype had an increased risk of lymph node metastasis in gastric cancer. • The A allele of rs1057147 had a stronger association with lymph node metastasis than the G allele. • The binding mode of miR-3144-5p or miR-3619-3p to MSLN was altered by the mutation of rs1057147.

Survival benefit of primary tumor resection for gastric cancer with liver metastasis: A propensity score-matched, population-based study

OBJECTIVES

Gastric cancer with liver metastasis (GCLM) is highly aggressive and has a poor prognosis. This study aims to evaluate the survival benefit of primary tumor resection (PTR) for gastric cancer with liver metastasis.

METHODS

Data on patients with GCLM was extracted from the Surveillance, Epidemiology, and End Results (SEER) database from 2010 to 2015. A 1:1 propensity score matching (PSM) analysis was performed to minimize the heterogeneity between the PTR and no-PTR groups. The Kaplan-Meier method and Cox regression analysis were used to assess the impact of primary tumor resection (PTR) on overall survival (OS) and cause-specific survival (CSS).

RESULTS

A total of 3,001 patients with GCLM were included, with 328 patients treated with primary tumor resection (PTR), whereas the other 2,673 patients were not. Patients with PTR had a significantly higher OS and CSS rate than those without PTR in unmatched and PSM cohorts. In an unmatched cohort, the median OS was 12.0 months (95% CI, 10 months to 14 months) for those who underwent PTR and 4 months (95% CI, 4 months to 5 months) for those without PTR; the median CSS for those who underwent PTR was 12.0 months (95% CI, 10 months to14 months) and 4 months (95% CI, 4 months to 5 months) for those without PTR, respectively. After PMS, the median OS was 12.0 months (95% CI, 10 months to 17 months) for those who underwent PTR and 7 months (95% CI, 5 months to 10 months) for those without PTR, respectively; the median CSS for those who underwent PTR was 12.0 months (95% CI, 11 months to 17 months) and 7 months (95% CI, 5 months to 8 months) for those without PTR, respectively. In addition, multivariate Cox analysis in the PSM cohort showed that PTR, age, degree of tumor differentiation, and chemotherapy were independent prognostic factors for OS and CSS in GCLM. Specifically, PTR was a significant protective factor for OS (HR: 0.427; 95% CI, 0.325 to 0.561, P <0.001) and CSS (HR: 0.419; 95% CI, 0.313 to 0.561, P <0.001).

CONCLUSION

Primary tumor resection improves the survival of gastric cancer patients with liver metastasis.

Single-cell RNA-seq dissecting heterogeneity of tumor cells and comprehensive dynamics in tumor microenvironment during lymph nodes metastasis in gastric cancer

Lymph node metastasis is the common metastasis route of gastric cancer. However, until now, heterogeneities of tumor cells and tumor microenvironment in primary tumors (PT) and metastatic lymph nodes (MLN) of gastric cancer (GC) remains uncharacterized. In this study, scRNA-seq was performed on tissues from PT and MLN of gastric cancer. Trajectory analysis and function enrichment analyses were conducted to decode the underlying mechanisms contributing to LN metastasis of gastric cancer. Heterogeneous composition of immune cells and distant intercellular interactions in PT and MLN were analyzed. Based on the generated single cell transcriptome profiles, dynamics of gene expressions in cancer cells between PT and MLN were characterized. Moreover, we reconstructed the developmental trajectory of GC cells' metastasis to LN and identified two sub-types of GC cells with distinct potentials of having malignant biological behaviors. We characterized the repression of neutrophil polarization associated genes, like LCN2, which would contribute to LN metastasis, and histochemistry experiments validated our findings. Additionally, heterogeneity in neutrophils, rather than macrophages, was characterized. Immune checkpoint associated interaction of SPP1 was found active in MLN. In conclusion, we decode the dynamics of tumor cells during LN metastasis in GC and to identify a sub-type of GC cells with potentials of LN metastasis. Our data indicated that the disordering the neutrophils polarization and maturation and the activation of immune checkpoint SPP1 might contribute to LN metastasis in GC, providing a novel insight on the mechanism and potential therapeutic targets of LN metastasis in GC. This article is protected by copyright. All rights reserved.

Heterogeneity of the tumor immune microenvironment and its clinical relevance

During the course of tumorigenesis and subsequent metastasis, malignant cells gradually diversify and become more heterogeneous. Consequently, the tumor mass might be infiltrated by diverse immune-related components, including the cytokine/chemokine environment, cytotoxic activity, or immunosuppressive elements. This immunological heterogeneity is universally presented spatially or varies temporally along with tumor evolution or therapeutic intervention across almost all solid tumors. The heterogeneity of anti-tumor immunity shows a profound association with the progression of disease and responsiveness to treatment, particularly in the realm of immunotherapy. Therefore, an accurate understanding of tumor immunological heterogeneity is essential for the development of effective therapies. Facilitated by multi-regional and -omics sequencing, single cell sequencing, and longitudinal liquid biopsy approaches, recent studies have demonstrated the potential to investigate the complexity of immunological heterogeneity of the tumors and its clinical relevance in immunotherapy. Here, we aimed to review the mechanism underlying the heterogeneity of the immune microenvironment. We also explored how clinical assessments of tumor heterogeneity might facilitate the development of more effective personalized therapies.

PIK3CA-AKT pathway predominantly acts in developing ipsilateral breast tumor recurrence long after breast-conserving surgery

PURPOSE

Ipsilateral breast tumor recurrence (IBTR) after breast-conserving therapy is seen after a long interval, but the clinical classification of Residual Tumor Recurrence (RR) or Double Primary (DP) needs to be validated. We used genome profiling to identify the genetic alterations associated with IBTR.

METHODS

Among 1881 breast cancer patients treated with breast-conserving therapy between 1999 and 2018, IBTR occurred in 52 patients (2.8%). Of these 22 patients who consented for genomic analysis of Primary Breast Cancer (T1) and IBTR (T2) were studied. When the same gene mutations in T1 and T2 were identified, it was classified as genomic residual recurrence gRR, and when no shared mutations identified, it was classified as gDP. The differences between clinical and genomic classification were compared. Furthermore, the pathway of the genes which were responsible for recurrence was also examined.

RESULTS

Of 13 clinically diagnosed RRs (cRRs), 11 were gRR and 2 were gDPs, while of 9 cDPs, 6 were gDP and 3 gRR, with a match rate of 17/22 (77%). We searched for genes involved in IBTR: PIK3CA-AKT pathway mutations were found in 12 of 14 gRRs (86%) in T1, and only 2 of 8 gDPs (25%) with significant difference (p = 0.004). When both of PBC and IBTR compared, PIK3CA-AKT pathway abnormalities were 24/28 (86%) in the gRR and 5/16 (31%) in the gDP (p < 0.001).

CONCLUSIONS

Genome profiling revealed that abnormalities in the PIK3CA-AKT pathway in long-term residential recurrences and are a crucial molecular group in the development of IBTR.

Bacterial Involvement in Progression and Metastasis of Colorectal Neoplasia

While the gut microbiome is composed of numerous bacteria, specific bacteria within the gut may play a significant role in carcinogenesis, progression, and metastasis of colorectal carcinoma (CRC). Certain microbial species are known to be associated with specific cancers; however, the interrelationship between bacteria and metastasis is still enigmatic. Mounting evidence suggests that bacteria participate in cancer organotropism during solid tumor metastasis. A critical review of the literature was conducted to better characterize what is known about bacteria populating a distant site and whether a tumor depends upon the same microenvironment during or after metastasis. The processes of carcinogenesis, tumor growth and metastatic spread in the setting of bacterial infection were examined in detail. The literature was scrutinized to discover the role of the lymphatic and venous systems in tumor metastasis and how microbes affect these processes. Some bacteria have a potent ability to enhance epithelial–mesenchymal transition, a critical step in the metastatic cascade. Bacteria also can modify the microenvironment and the local immune profile at a metastatic site. Early targeted antibiotic therapy should be further investigated as a measure to prevent metastatic spread in the setting of bacterial infection.

Mapping the genomic diaspora of gastric cancer

Gastric cancer (GC) is a leading contributor to global cancer incidence and mortality. Pioneering genomic studies, focusing largely on primary GCs, revealed driver alterations in genes such as ERBB2, FGFR2, TP53 and ARID1A as well as multiple molecular subtypes. However, clinical efforts targeting these alterations have produced variable results, hampered by complex co-alteration patterns in molecular profiles and intra-patient genomic heterogeneity. In this Review, we highlight foundational and translational advances in dissecting the genomic cartography of GC, including non-coding variants, epigenomic aberrations and transcriptomic alterations, and describe how these alterations interplay with environmental influences, germline factors and the tumour microenvironment. Mapping of these alterations over the GC life cycle in normal gastric tissues, metaplasia, primary carcinoma and distant metastasis will improve our understanding of biological mechanisms driving GC development and promoting cancer hallmarks. On the translational front, integrative genomic approaches are identifying diverse mechanisms of GC therapy resistance and emerging preclinical targets, enabled by technologies such as single-cell sequencing and liquid biopsies. Validating these insights will require specifically designed GC cohorts, converging multi-modal genomic data with longitudinal data on therapeutic challenges and patient outcomes. Genomic findings from these studies will facilitate 'next-generation' clinical initiatives in GC precision oncology and prevention.

Collective metastasis: coordinating the multicellular voyage

The metastatic process is arduous. Cancer cells must escape the confines of the primary tumor, make their way into and travel through the circulation, then survive and proliferate in unfavorable microenvironments. A key question is how cancer cells overcome these multiple barriers to orchestrate distant organ colonization. Accumulating evidence in human patients and animal models supports the hypothesis that clusters of tumor cells can complete the entire metastatic journey in a process referred to as collective metastasis. Here we highlight recent studies unraveling how multicellular coordination, via both physical and biochemical coupling of cells, induces cooperative properties advantageous for the completion of metastasis. We discuss conceptual challenges and unique mechanisms arising from collective dissemination that are distinct from single cell-based metastasis. Finally, we consider how the dissection of molecular transitions regulating collective metastasis could offer potential insight into cancer therapy.

Mechanisms of breast cancer metastasis

Invasive breast cancer tends to metastasize to lymph nodes and systemic sites. The management of metastasis has evolved by focusing on controlling the growth of the disease in the breast/chest wall, and at metastatic sites, initially by surgery alone, then by a combination of surgery with radiation, and later by adding systemic treatments in the form of chemotherapy, hormone manipulation, targeted therapy, immunotherapy and other treatments aimed at inhibiting the proliferation of cancer cells. It would be valuable for us to know how breast cancer metastasizes; such knowledge would likely encourage the development of therapies that focus on mechanisms of metastasis and might even allow us to avoid toxic therapies that are currently used for this disease. For example, if we had a drug that targeted a gene that is critical for metastasis, we might even be able to cure a vast majority of patients with breast cancer. By bringing together scientists with expertise in molecular aspects of breast cancer metastasis, and those with expertise in the mechanical aspects of metastasis, this paper probes interesting aspects of the metastasis cascade, further enlightening us in our efforts to improve the outcome from breast cancer treatments.

Elements and evolutionary determinants of genomic divergence between paired primary and metastatic tumors

Can metastatic-primary (M-P) genomic divergence measured from next generation sequencing reveal the natural history of metastatic dissemination? This remains an open question of utmost importance in facilitating a deeper understanding of metastatic progression, and thereby, improving its prevention. Here, we utilize mathematical and computational modeling to tackle this question as well as to provide a framework that illuminates the fundamental elements and evolutionary determinants of M-P divergence. Our framework facilitates the integration of sequencing detectability of somatic variants, and hence, paves the way towards bridging the measurable between-tumor heterogeneity with analytical modeling and interpretability. We show that the number of somatic variants of the metastatic seeding cell that are experimentally undetectable in the primary tumor, can be characterized as the path of the phylogenetic tree from the last appearing variant of the seeding cell back to the most recent detectable variant. We find that the expected length of this path is principally determined by the decay in detectability of the variants along the seeding cell's lineage; and thus, exhibits a significant dependence on the underlying tumor growth dynamics. A striking implication of this fact, is that dissemination from an advanced detectable subclone of the primary tumor can lead to an abrupt drop in the expected measurable M-P divergence, thereby breaking the previously assumed monotonic relation between seeding time and M-P divergence. This is emphatically verified by our single cell-based spatial tumor growth simulation, where we find that M-P divergence exhibits a non-monotonic relationship with seeding time when the primary tumor grows under branched and linear evolution. On the other hand, a monotonic relationship holds when we condition on the dynamics of progressive diversification, or by restricting the seeding cells to always originate from undetectable subclones. Our results highlight the fact that a precise understanding of tumor growth dynamics is the sine qua non for exploiting M-P divergence to reconstruct the chronology of metastatic dissemination. The quantitative models presented here enable further careful evaluation of M-P divergence in association with crucial evolutionary and sequencing parameters.