Truncation- and motif-based pan-cancer analysis reveals tumor-suppressing kinases

A major challenge in cancer genomics is identifying "driver" mutations from the many neutral "passenger" mutations within a given tumor. To identify driver mutations that would otherwise be lost within mutational noise, we filtered genomic data by motifs that are critical for kinase activity. In the first step of our screen, we used data from the Cancer Cell Line Encyclopedia and The Cancer Genome Atlas to identify kinases with truncation mutations occurring within or before the kinase domain. The top 30 tumor-suppressing kinases were aligned, and hotspots for loss-of-function (LOF) mutations were identified on the basis of amino acid conservation and mutational frequency. The functional consequences of new LOF mutations were biochemically validated, and the top 15 hotspot LOF residues were used in a pan-cancer analysis to define the tumor-suppressing kinome. A ranked list revealed MAP2K7, an essential mediator of the c-Jun N-terminal kinase (JNK) pathway, as a candidate tumor suppressor in gastric cancer, despite its mutational frequency falling within the mutational noise for this cancer type. The majority of mutations in MAP2K7 abolished its catalytic activity, and reactivation of the JNK pathway in gastric cancer cells harboring LOF mutations in MAP2K7 or the downstream kinase JNK suppressed clonogenicity and growth in soft agar, demonstrating the functional relevance of inactivating the JNK pathway in gastric cancer. Together, our data highlight a broadly applicable strategy to identify functional cancer driver mutations and define the JNK pathway as tumor-suppressive in gastric cancer.

Canine osteogenic sarcoma treated by amputation and MER: an adverse effect of splenectomy on survival

Canine and human osteogenic sarcomas, like most other malignant tumors, cause or are associated with progressive impairment of host immune reactivity. Adjuvant immunotherapy with live BCG had shown increased survival in one study of canine disease. Experiments with induced fibrosarcomas in mice had suggested that some of the host immune defect might be ameliorated by splenectomy. A prospective clinical trial was conducted with several cooperating veterinary centers. Dogs with osteosarcoma apparently confined to a limb were randomized to be treated by amputation and methanol-extracted residue of BCG (MER), or by the same modalities plus splenectomy. Randomization was discontinued relatively early in the study because of higher mortality in the splenectomy group. Animals treated by amputation and MER could be compared only with historic controls; median and one-year survival rates did not differ significantly from those of prior series. Animals treated by amputation, splenectomy, and MER had significantly poorer survival.