The development of noninvasive methods to detect and monitor tumors continues to be a major challenge in oncology. We used digital polymerase chain reaction–based technologies to evaluate the ability of circulating tumor DNA (ctDNA) to detect tumors in 640 patients with various cancer types. We found that ctDNA was detectable in >75% of patients with advanced pancreatic, ovarian, colorectal, bladder, gastroesophageal, breast, melanoma, hepatocellular, and head and neck cancers, but in less than 50% of primary brain, renal, prostate, or thyroid cancers. In patients with localized tumors, ctDNA was detected in 73, 57, 48, and 50% of patients with colorectal cancer, gastroesophageal cancer, pancreatic cancer, and breast adenocarcinoma, respectively. ctDNA was often present in patients without detectable circulating tumor cells, suggesting that these two biomarkers are distinct entities. In a separate panel of 206 patients with metastatic colorectal cancers, we showed that the sensitivity of ctDNA for detection of clinically relevant KRAS gene mutations was 87.2% and its specificity was 99.2%. Finally, we assessed whether ctDNA could provide clues into the mechanisms underlying resistance to epidermal growth factor receptor blockade in 24 patients who objectively responded to therapy but subsequently relapsed. Twenty-three (96%) of these patients developed one or more mutations in genes involved in the mitogen-activated protein kinase pathway. Together, these data suggest that ctDNA is a broadly applicable, sensitive, and specific biomarker that can be used for a variety of clinical and research purposes in patients with multiple different types of cancer.

Somatic L1 retrotransposition events have been shown to occur in epithelial cancers. Here, we attempted to determine how early somatic L1 insertions occurred during the development of gastrointestinal (GI) cancers. Using L1-targeted resequencing (L1-seq), we studied different stages of four colorectal cancers arising from colonic polyps, seven pancreatic carcinomas, as well as seven gastric cancers. Surprisingly, we found somatic L1 insertions not only in all cancer types and metastases but also in colonic adenomas, well-known cancer precursors. Some insertions were also present in low quantities in normal GI tissues, occasionally caught in the act of being clonally fixed in the adjacent tumors. Insertions in adenomas and cancers numbered in the hundreds, and many were present in multiple tumor sections, implying clonal distribution. Our results demonstrate that extensive somatic insertional mutagenesis occurs very early during the development of GI tumors, probably before dysplastic growth.

Purpose Hepatocellular carcinoma (HCC) often arises in the setting of chronic liver inflammation and may be responsive to novel immunotherapies. Experimental Design To characterize the immune microenvironment in HCC, IHC staining was performed for CD8-positive T lymphocytes, PD-1–positive, and LAG-3–positive lymphocytes, CD163-positive macrophages, and PD-L1 expression in tumor and liver background from 29 cases of resected HCC. Results Expression of CD8 was reduced in tumor, and expression of CD163 was reduced at the tumor interface. Positive clusters of PD-L1 expression were identified in 24 of 29 cases (83%), and positive expression of LAG-3 on tumor-infiltrating lymphocytes was identified in 19 of 29 cases (65%). The expression of both PD-L1 and LAG-3 was increased in tumor relative to liver background. No association between viral status or other clinicopathologic features and expression of any of the IHC markers investigated was noted. Conclusions LAG-3 and PD-L1, two inhibitory molecules implicated in CD8 T-cell tolerance, are increased in most HCC tumors, providing a basis for investigating combinatorial checkpoint blockade with a LAG-3 and PD-L1 inhibitor in HCC.