#  KGCRF Poster Competition Winners 2023 

 



## **KGCRF Rising Young Scientist Award – up to & including G3s**

### **ALICE BERTOCCHI | G3**  
*Immunology*  
*Stephanie Dougan and Judith Agudo Labs*

**B cells facilitate lymph node colonization in pancreatic ductal adenocarcinoma**  
Pancreatic ductal adenocarcinoma (PDAC) has a low survival rate. Several factors contribute to its dismal prognosis, including resistance to available therapies and high invasiveness. Lymph nodes act as an early systemic source of circulating malignant cells in PDAC, allowing their dissemination to other organs early in disease progression. Lymphatic colonization is linked to worse prognosis. Therefore, a better understanding of mechanisms regulating lymph node metastasis is clinically needed. To study each step in the metastatic cascade to the lymph nodes, we have developed a mouse co-clinical model of resectable pancreatic cancer. This model consists of subcutaneous injection of highly metastatic pancreatic cancer cells, followed by surgical resection of the primary tumor. Following resection, mice spontaneously develop lymph nodes metastasis at a comparable frequency to human PDAC post-surgical recurrence, on a similar time scale relative to the lifespans of mice and humans. Expression of nuclear tdTomato allows detection of single cancer cells seeding draining lymph nodes very early in disease progression, even before metastases are histological detectable. Using this model, we gain insights into the first steps of metastatic seeding of lymph nodes. These findings will enhance our understanding of lymphatic colonization in PDAC and potentially inform immunotherapeutic interventions to disrupt the metastatic cascade.

### **TENG GAO | G3**  
*Bioinformatics and Integrative Genomics*  
*Peter Park Lab*

**Haplotype-aware analysis of somatic copy number variations from single-cell transcriptomes**  
Genome instability and aberrant alterations of transcriptional programs both play important roles in cancer. Single-cell RNA sequencing (scRNA-seq) has the potential to investigate both genetic and nongenetic sources of tumor heterogeneity in a single assay. Here we present a computational method, Numbat, that integrates haplotype information obtained from population-based phasing with allele and expression signals to enhance detection of copy number variations from scRNA-seq. Numbat exploits the evolutionary relationships between subclones to iteratively infer single-cell copy number profiles and tumor clonal phylogeny. Analysis of 22 tumor samples, including multiple myeloma, gastric, breast and thyroid cancers, shows that Numbat can reconstruct the tumor copy number profile and precisely identify malignant cells in the tumor microenvironment. We identify genetic subpopulations with transcriptional signatures relevant to tumor progression and therapy resistance. Numbat requires neither sample-matched DNA data nor a priori genotyping, and is applicable to a wide range of experimental settings and cancer types.

## **KGCRF Early Career Investigator Award – G4s & up**

### **EMMA GARCIA | G4**  
*Chemical Biology*  
*Brian Liau Lab*

**Elucidating the role of protein oligomerization in the mechanism of the dominant-negative DNMT3A hotspot mutation R882H**  
DNA methyltransferase 3A (DNMT3A) is one of the two human de novo DNA methyltransferases responsible for establishing DNA methylation during development, and is frequently mutated in hematopoietic disorders, including clonal hematopoiesis and acute myeloid leukemia (AML). One hotspot mutation, R882H, likely causes a dominant loss-of-function phenotype, but its mechanism of doing so remains controversial. DNMT3A is typically found as a tetramer and R882 is found at one of its two oligomerization interfaces. However, it is debated in the field whether this mutation perturbs the multimeric state of DNMT3A, and if so whether it breaks up tetramers or promotes oligomerization. We aim to determine how the R882H mutation causes a dominant negative phenotype and to describe new mechanisms of DNMT3A regulation that could be therapeutically targeted. Towards this goal, we have shown with purified protein and in cell lysate that DNMT3AR882H is more likely to form macro-oligomers than WT DNMT3A. We have also obtained preliminary data indicating that the regulatory PWWP domain of the enzyme is involved in DNMT3A multimerization. By further characterizing the biochemical factors contributing to DNMT3A oligomerization, we hope to elucidate novel mechanisms of DNMT3A regulation that could be exploited for the treatment of hematopoietic disorders.

### **PARIS PALLIS | G6**  
*Immunology*  
*Ulrich Von Andrian Lab*

**Gatekeepers: How Endothelial Cell Identity control Tumor T-cell infiltration**  
The success of virtually all cancer immunotherapies, such as checkpoint blockade or adoptive cell transfer, is contingent on the accessibility of solid tumors by cytotoxic T-cells. In infection settings, T-cells can enter inflamed tissues by extravasating from the blood stream at specific segments of the vasculature. These segments, namely post-capillary venules, are lined by specialized endothelial cells that can support the leukocyte adhesion cascade and transmigration of such T-cells. Solid cancers produce an excess of pro-angiogenic signals to induce vascularization and support their energetic and metabolic needs. This pro-angiogenic milieu leads to abnormalities in vascular differentiation and structure and can disrupt the maturation of endothelial cells.

Here, we show that venular differentiation is blunted in tumor endothelial cells, affecting T-cell infiltration and responsiveness to checkpoint blockade. Consequently, T-cell rich tumors that are responsive to immunotherapy have a higher proportion of intratumoral venules. Further, while peritumoral venules are functional and can recruit T-cells to the periphery, these cells fail to penetrate the tumor tissue. Decreasing or increasing the number of venules can shift the number of infiltrating T-cells accordingly and prime the tumor for immunotherapy. Importantly, traditional vascular normalization approaches do not increase the number of venules within the tumor.