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Supplementary Figure S1 shows genetic dependency profiles for BRAF, MAPK1 (ERK2), and MAPK3 (ERK1) by BRAFV600 mutation status from three independent screens: DRIVE, ACHILLES, and AVANA.

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All supplementary figure and table titles and legends.

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Half of advanced human melanomas are driven by mutant BRAF and dependent on MAPK signaling. Interestingly, the results of three independent genetic screens highlight a dependency of BRAF-mutant melanoma cell lines on BRAF and ERK2, but not ERK1. ERK2 is expressed higher in melanoma compared with other cancer types and higher than ERK1 within melanoma. However, ERK1 and ERK2 are similarly required in primary human melanocytes transformed with mutant BRAF and are expressed at a similar, lower amount compared with established cancer cell lines. ERK1 can compensate for ERK2 loss as seen by expression of ERK1 rescuing the proliferation arrest mediated by ERK2 loss (both by shRNA or inhibition by an ERK inhibitor). ERK2 knockdown, as opposed to ERK1 knockdown, led to more robust suppression of MAPK signaling as seen by RNA-sequencing, qRT-PCR, and Western blot analysis. In addition, treatment with MAPK pathway inhibitors led to gene expression changes that closely resembled those seen upon knockdown of ERK2 but not ERK1. Together, these data demonstrate that ERK2 drives BRAF-mutant melanoma gene expression and proliferation as a function of its higher expression compared with ERK1. Selective inhibition of ERK2 for the treatment of melanomas may spare the toxicity associated with pan-ERK inhibition in normal tissues.Implications:BRAF-mutant melanomas overexpress and depend on ERK2 but not ERK1, suggesting that ERK2-selective inhibition may be toxicity sparing.

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The chromosome 9p21 (chr9p21) locus is deleted in almost 10% of all cancer types. This locus includes the CDKN2A gene that encodes the critical tumor suppressors p19-ARF and p16-INK4a. Methylthioadenosine phosphorylase (MTAP), a gene proximal to CDKN2A, is co-deleted in 80%-90% of tumors with CDKN2A deletion. MTAP plays a critical role in the methionine salvage pathway, and the deletion of MTAP results in the accumulation of its substrate methythioadenosine (MTA). Accumulation of MTA partially inhibits the activity of the arginine methyltransferase PRMT5, causing MTAP deficient cancer cells to be more sensitive to the genetic knockdown of PRMT5. In contrast to genetic knockdown, sensitivity to pharmacological inhibition of PRMT5 does not appear to stratify with MTAP status. However, currently known PRMT5 inhibitors all possess SAM competitive or uncompetitive MOIs, which generally require displacement of MTA from the active site for binding. We hypothesize that leveraging the high MTA state induced by MTAP deficiency will require an inhibitor that can bind PRMT5 without disrupting bound MTA. Here we report the discovery of a PRMT5 inhibitor with a novel binding mode that is compatible with MTA binding. While this compound possesses the desired MOI, it shows only modestly increased potency toward MTAP-null cells. Mathematical simulations of different inhibitor mechanisms indicate that the degree of selectivity that can be achieved depends on the difference in MTA levels between MTAP-null and WT cells. Our in vitro data suggest that the elevation in intracellular MTA concentrations that occurs with MTAP deletion is not sufficient to confer significantly increased sensitivity to PRMT5 inhibition. We anticipate that the therapeutic index that can be achieved between MTAP-null tumor cells and PRMT5-sensitive normal tissues will be similarly limited in vivo. Citation Format: Rohit Malik, Peter K. Park, Christopher M. Barbieri, Yuval Blat, Steven Sheriff, Carolyn A. Weigelt, Lisa M. Kopcho, Muge Celiktas, Max Ruzanov, Joseph G. Naglich, Jennifer L. Price, Mary Harner, Kevin M. Omalley, JIngjing Deng, William Schmitz, Guo Li, Zheming Ruan, Lan-ying Qin, Gerald J. Duke, Iyoncy Rodrigo, Mark R. Witmer, David G. Harden, Shilpa Demes, Brian J. Arey, Matt Soars, Brian E. Fink, Ashvinikumar V. Gavai, Gregory D. Vite, Charles F. Voliva. A novel MTA non-competitive PRMT5 inhibitor [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1140.

720 Background: Clear cell renal cell carcinoma (ccRCC) is the most common subtype of kidney cancer comprising up to 80% of RCC. Anti-vascular endothelial growth factor receptor (VEGFR) is a common therapy. Immune checkpoint inhibitor therapy with anti-PD1 antibody Nivolumab is a standard second line option in mccRCC. Overall response rate with Nivolumab however is only 25%. Since there is a critical need to develop and refine predictive biomarkers for anti-PD1 checkpoint inhibitor immunotherapy, we undertook a genomics based approach to gain further insights. Methods: Archival pre-treatment tissues from 37 metastatic mccRCC patients who had received anti-VEGFR first and then Nivolumab were collected and profiled by integrated next generation sequencing (NGS) including whole exome sequencing and RNA sequencing. Integrative NGS analysis was used to discover somatic mutations, indels, copy-number alterations and gene expression changes among the samples in this cohort. In-addition, we characterized the T-Cell clone type by adaptive immunoSEQ TCR sequencing on the matched tumor/benign adjacent tissue samples. Clinical outcome data was correlated with high throughput sequencing results to delineate the characteristics of responders and non-responders. Results: Integrative NGS profiling and analysis of ccRCC tumors revealed 1) the characteristic copy number alteration including frequent loss at 3p, 8p21.3 and 9p21.3 as well as gain at 5q, and 12p12.1. 2) a low mutational burden 3) tumors with PBRM1 mutation were relatively enriched in the “No Clinical Benefit Category”. 4) CD8 immunohistochemistry showed significant enrichment of CD8+ cells ( pval-0.05) in the clinical benefit group compared to patients with no-clinical benefit. The clinical benefit group tended to have higher number of TCR clones. Conclusions: Integrative genomic sequencing analysis of ccRCC tumors in Nivolumab treated patients revealed CD8 expression as a putative biomarker. Greater T-cell clonotypes & clonal expansion correlated with clinical benefit. PBRM1 mutant status did not select for clinical benefit. A model combining CD8 expression with T-cell characteristics was developed.

Therapeutic options for the treatment of an increasing variety of cancers have been expanded by the introduction of a new class of drugs, commonly referred to as checkpoint blocking agents, that target the host immune system to positively modulate anti-tumor immune response. Although efficacy of these agents has been linked to a pre-existing level of tumor immune infiltrate, it remains unclear why some patients exhibit deep and durable responses to these agents therapy while others do not benefit. To examine the influence of tumor genetics on tumor immune state, we interrogated the relationship between somatic mutation and copy number alteration with infiltration levels of 7 immune cell types across 40 tumor cohorts in The Cancer Genome Atlas. Levels of cytotoxic T, regulatory T, total T, natural killer, and B cells, as well as monocytes and M2 macrophages, were estimated using a novel set of transcriptional signatures that were designed to resist interference from the cellular heterogeneity of tumors. Tumor mutational load and estimates of tumor purity were included in our association models to adjust for biases in multi-modal genomic data. Copy number alterations, mutations summarized at the gene level, and position-specific mutations were evaluated for association with tumor immune infiltration. We observed a strong relationship between copy number loss of a large region of chromosome 9p and decreased lymphocyte estimates in melanoma, pancreatic, and head/neck cancers. Mutations in the oncogenes PIK3CA, FGFR3, and RAS/RAF family members, as well as the tumor supressor TP53, were linked to changes in immune infiltration, usually in restricted tumor types. Associations of specific WNT/beta-catenin pathway genetic changes with immune state were limited, but we noted a link between 9p loss and the expression of the WNT receptor FZD3, suggesting that there are interactions between 9p alteration and WNT pathways. Finally, two different cell death regulators, CASP8 and DIDO1, were often mutated in head/neck tumors that had higher lymphocyte infiltrates. In summary, our study supports the relevance of tumor genetics to questions of efficacy and resistance in checkpoint blockade therapies. It also highlights the need to assess genome-wide influences during exploration of any specific tumor pathway hypothesized to be relevant to therapeutic response. Some of the observed genetic links to immune state, like 9p loss, may influence response to cancer immune therapies. Others, like mutations in cell death pathways, may help guide combination therapeutic approaches.

Antibodies are immune proteins which specifically recognize and bind foreign macromolecules (antigens) and are critical in protective immune responses to viruses and other pathogens. Their exquisite specificity of binding, as well as their relative ease of production, have made antibodies invaluable reagents in biotechnology, and antibodies to dendritic polymers would presumably be similarly powerful, were they available. We have developed methods for generating and detecting antibody responses to PAMAM dendrimers, and have partially defined the recognition specificities of those antibodies. Furthermore, we have used the antibodies in multiple immune detection procedures. We also propose applications of our antibodies to assemble defined supramolecular assemblies of dendrimers and to pattern the surface of dendrimers. Our results and those of others suggest that it may be possible to generate antibodies to many synthetic nanostructures, and that these reagents should have numerous applications in nanotechnology.

The octamer binding site, which is located immediately upstream of the poorly conserved DRA TATA sequence, is important for high levels of expression of this human major histocompatibility class II gene in B cells. In this study, we demonstrate that the substitution of the DRA TATA sequence with the TATA box from the adenovirus E1b promoter removes the requirement for the octamer binding site for high levels of expression from the DRA promoter. Since only the TATA box from the E1b but not the DRA promoters binds the TATA binding protein, we conclude that the octamer binding site helps to recruit TBP to the DRA promoter.

DNA sequence analysis of a region contained within a large, interspersed repetitive family of mice reveals a long open reading frame. This sequence extends 978 base pairs between two stop codons, creating a reading frame that is open for 326 amino acids. The DNA sequence in this region is conserved between three distantly related Mus species, as well as between mouse and monkey, in a manner that is characteristic of regions undergoing selection for protein function.

Clones containing five non-adult beta-globin genes were isolated from a library of BALB/c DNA. Together, the newly cloned regions comprise a contiguous block of 32 kb of the mouse genome. Restriction mapping of genomic DNA established the physical linkage of these non-adult genes to the two adult beta-globin genes as well as the two adult genes to each other. Thus this entire BALB/c beta-globin complex consists of seven linked genes, all with the same transcriptional orientation, arrayed over 70 kb of DNA. The order of these genes is: 5'-epsilon y3-beta h0-beta h1-beta h2-beta h3-beta major-beta minor-3' Portions of each of the five newly identified genes have been sequenced. Only one, epsilon y3, encodes a previously described globin. beta h0 and beta h1, which are closely related, differ significantly from both adult and embryonic globins. The beta h2 sequence is more closely related to the adult genes than to the other non-adult genes. However, it is the sequence least homologous to both of these classes. The 5' half of the beta h3 gene (preceding codon 75) has an aberrant structure. The rest of this sequence is intact, resembling an adult beta-globin gene except for an inserted base at cocon 90, resulting in a frameshift. Consequently, the beta h3 sequence cannot be translated to produce a normal beta-globin.

We have determined the complete nucleotide sequence for five members of the L1Md repetitive family from the beta-globin gene region of the BALB/c mouse. The five repeats are different lengths, each terminating at the 5′ end at different points with respect to one another. We have analyzed the nucleotides around the endpoints of the five repeats for clues as to the mechanisms involved with the dispersal and 5′ truncation of this repeat family. Each L1 member is flanked by a pair of short direct repeats. Since these direct repeats differ in length and sequence in each of the five cases, the dispersal mechanism does not involve a sequence targeted process. The sequence at the 3′ end is conserved and its organization resembles the 3′ end of a polyadenylated RNA, suggesting that transcripts of the repeat are involved in the dispersal process either directly or as intermediates in the generation of complementary DNA copies of the sequence. One of the L1 repeats is a recent insertion, since it is found in the Hbb d chromosome, but not in the Hbb s chromosome. This suggests a dispersal process that has been active as recently as 4 million years ago.

A 300-bp DNA sequence has been determined for 30 (10 from each of three species of mice) random isolates of a subset of the long interspersed repeat family L1. From these data we conclude that members of the L1 family are evolving in concert at the DNA sequence level in Mus domesticus, Mus caroli, and Mus platythrix. The mechanism responsible for this phenomenon may be either duplicative transposition, gene conversion, or a combination of the two. The amount of intraspecies divergence averages 4.4%, although between species base substitutions accumulate at the rate of approximately 0.85%/Myr to a maximum divergence of 9.1% between M. platythrix and both M. domesticus and M. caroli. Parsimony analysis reveals that the M. platythrix L1 family has evolved into a distinct clade in the 10-12 Myr since M. platythrix last shared a common ancestor with M. domesticus and M. caroli. The parsimony tree also provides a means to derive the average half-life of L1 sequences in the genome. The rates of gain and loss of individual copies of L1 were estimated to be approximately equal, such that approximately one-half of them turn over every 3.3 Myr.

We have characterized a large repetitive element which has been found at seven different locations within the beta globin locus of the BALB/c mouse. This repeat has an unusual structure in that each of the different members has the same end of the element conserved while the other end terminates at a different point in each repeat member. The sequences within the repeats from the beta globin locus have homology with other repetitive families such as the MIF-1, Bam-5, R, and the BamH1 families. These were recently proposed (T. Fanning, (1983) Nucleic Acids Res. 11, 5073-5091) to be part of a structure with the same organization which we found in the globin locus. Probing plaques from a BALB/c genomic library with sequences derived from the repeats in the globin locus shows that virtually all of the repeats from this family are organized in a manner consistent with the proposed structure.

We report an investigation of the structure, evolutionary history, and function of the highly repeated DNA family named Long Interspersed Sequence One (L1). Hybridization studies show, first, that L1 is present throughout marsupial and placental mammalian orders. Second, L1 is more homologous within these species than between them, which suggests that it has undergone concerted evolution within each mammalian lineage. Third, on the whole L1 diverges in accordance with the fossil record. This suggests that it arose in each lineage rather by inheritance from a common ancestral family, which was present in the progenitor to mammals, than by cross-species transmission. Alignment of 1.6 X 10(3) bases of primate and mouse L1 DNA sequences shows a predominance of silent mutations within aligned long open reading frames, indicating that at least this part of L1 has produced functional protein. The observation of additional long open reading frames in further unaligned DNA sequences suggests that a minimum of 3.2 X 10(3) bases or at least half of the L1 structure is a protein-coding sequence. Thus L1, which contains about 100,000 members in mouse, is by far the most repetitive family of which a subset comprises functional protein-encoding genes. The ability of the putative protein-encoding regions of mouse L1 to hybridize to L1 homologs throughout the Mammalia implies that these sequences have been subject to conservative selection upon protein function in all mammalian lineages, rather than in a few. L1 is therefore a highly repeated family of genes with both a widespread and an ancient history of function in mammals.

The nucleotide sequence of 55,856 base-pairs containing all seven beta-globin homologous structures from chromosome 7 of the BALB/c mouse is reported. This sequence links together previously published sequences of the beta-globin genes, pseudogenes and repetitive elements. Using low stringency computer searches, we found no additional beta-globin homologous sequences, but did find many more long interspersed repetitive sequences (L1) than predicted by hybridization. L1 is a major component of the mouse beta-globin complex with at least 15 elements comprising about 22% of the reported sequence. Most open reading frames greater than 300 base-pairs in the cluster overlap with L1 repeats or globin genes. Polypurine, polypyrimidine and alternating purine/pyrimidine tracts are not evenly dispersed throughout the complex, but they do not appear to be excluded from or restricted to particular regions. Several regions of intergenic homology were detected in dot-plot comparisons of the mouse sequence with itself and with the human beta-globin sequence. The significance of these homologies is unclear, but these regions are candidates for further study in functional assays in erythroid cell lines or transgenic animals.