Kaposi Sarcoma (KS) is an aggressive cancer caused by the Kaposi Sarcoma Herpesvirus (KSHV/HHV-8). Individuals with immunodeficiencies, exemplified by HIV, have an elevated risk of developing KS. However, understanding of the genetic factors contributing to KS progression is still limited. To explore potential genetic alterations in KS that could offer biological or therapeutic insights, whole exome sequencing was performed on 78 KS tumors and matching normal skin samples from 59 adults with KS (46 with HIV-associated KS and 13 with HIV-negative KS) receiving treatment at the Uganda Cancer Institute in Kampala, Uganda. Results showed a very low mutational burden in all samples except one (median = 11 mutations), which is the smallest number of mutations found across all 33 cancer types in The Cancer Genome Atlas (TCGA). No recurrent mutations were identified. Mutational signatures included impaired DNA mismatch repair and smoking. There was no evidence suggesting that multiple tumors from the same patient originated from a single clone. The number of genome copy alterations per genome was higher in tumors from individuals without HIV and those with advanced-stage disease. This suggests that lesions that take longer to develop may accumulate more alterations, although the overall number of alterations remains low compared to other cancers. These findings suggest that KS pathogenesis differs from other cancers, with KSHV viral infection and the expression of viral oncogenes being the primary drivers of carcinogenesis, rather than clonal oncogenic transformation arising from genetic alterations of cancer-related cellular genes.
Induced pluripotent stem cells (iPSCs) provide a modeling system for human disease within the critical context of the human genome. CRISPR editing of iPSCs allows the construction of isogenic pairs where the cells have nearly identical genomes except for the desired edited change. Here, we used CRISPR editing on a healthy control line to generate three new isogenic iPSC lines that each contains a different familial amyotrophic lateral sclerosis (fALS) mutation (TARDBP[G298S/+], SOD1[G85R/+], and PFN1[G118V/+]). As controls for each mutation, we retained iPSC lines that went through the editing process but did not have the desired heterozygous mutation. We have also performed editing in a patient cell line with a hexanucleotide repeat in C9ORF72. This edit mutates a non-canonical start codon upstream of the hexanucleotide repeat. These edited lines have been used in three different studies:(1) In “Human sensorimotor organoids derived from healthy and amyotrophic lateral sclerosis stem cells form neuromuscular junctions” (PMID: 34362895), we performed exome sequencing to confirm the absence of off-target CRISPR events. We also performed single-cell sequencing on sensorimotor organoids from a second healthy control iPSC line, which is deposited alongside the exome sequencing data.(2) In “iPSC motor neurons, but not other derived cell types, capture gene expression changes in postmortem sporadic ALS motor neurons (PMID: 37651231), we differentiated these isogenic lines into motor neurons, sensory neurons, cortical neurons, and astrocytes and then performed bulk RNA-sequencing. We then assessed similarities between fALS mutations, differences between cell types, and the capacity of iPSC modeling to capture differentially expressed genes in postmortem sporadic ALS motor neurons.(3) In "Blocking RAN translation without altering RNA foci rescues C9ORF72-related ALS/FTD phenotypes" (Jiang et al. 2025), we mutate a non-canonical start codon upstream of a hexanucleotide repeat in C9ORF72. This mitigates several phenotypes related to neurodegeneration.
