Highlights

SHP2 Inhibition Abrogates Adaptive Resistance to KRASG12C-Inhibition and Remodels the Tumor Microenvironment of KRAS-Mutant Tumors

ABSTRACT

KRAS is the most frequently mutated oncogene in human cancer, and KRAS inhibition has been a longtime therapeutic goal. Recently, inhibitors (G12C-Is) that bind KRASG12C-GDP and react with Cys-12 were developed. Using new affinity reagents to monitor KRASG12C activation and inhibitor engagement, we found that, reflecting its action upstream of SOS1/2, SHP2 inhibitors (SHP2-Is) increased KRAS-GDP occupancy, enhancing G12C-I efficacy. SHP2-Is abrogated feedback signaling by multiple RTKs and blocked adaptive resistance to G12C-Is in vitro, in xenografts, and in syngeneic KRASG12Cmutant pancreatic ductal adenocarcinoma (PDAC) and non-small cell lung cancer (NSCLC) models. Biochemical analysis revealed enhanced suppression of ERK-, MYC-, anti-apoptotic-, and cell-cycle genes, and increased pro-apoptotic gene expression in tumors from combination-treated mice. SHP2-I/G12C-I also evoked favorable changes in the immune microenvironment, decreasing myeloid suppressor cells, increasing CD8+ T cells, and sensitizing tumors to PD-1 blockade. Experiments using cells expressing inhibitor-resistant SHP2 showed that SHP2 inhibition in PDAC cells is required for tumor regression and remodeling of the immune microenvironment, but also revealed direct inhibitory effects on angiogenesis resulting in decreased tumor vascularity. Our results demonstrate that SHP2-I/G12C-I combinations confer a substantial survival benefit in PDAC and NSCLC and identify additional combination strategies for enhancing the efficacy of G12C-Is.

[preprint posted on bioRxiv 2020 May 31]

Genetically Defined, Syngeneic Organoid Platform for Developing Combination Therapies for Ovarian Cancer

SUMMARY

The paucity of genetically informed, immune-competent tumor models impedes evaluation of conventional, targeted, and immune therapies. By engineering mouse fallopian tube (FT) organoids using lentiviral gene transduction and/or CRISPR/Cas9 mutagenesis, we generated multiple high grade serous ovarian carcinoma (HGSOC) models exhibiting mutational combinations seen in patients. Detailed analysis of homologous recombination (HR)-proficient (Tp53-/-;Ccne1OE;Akt2OE; KrasOE), HR-deficient (Tp53-/-;Brca1-/-;MycOE) and unclassified (Tp53-/-;Pten-/-;Nf1-/-) organoids revealed differences in in vitro properties and tumorigenicity. Tumorigenic organoids had variable sensitivity to HGSOC chemotherapeutics and evoked distinct immune microenvironments. These findings enabled development of a chemotherapy/immunotherapy regimen that yielded durable, T-cell dependent responses in Tp53-/-;Ccne1OE;Akt2OE;Kras HGSOC; by contrast, Tp53-/-;Pten-/-;Nf1-/- tumors failed to respond. Genotype-informed, syngeneic organoid models could provide an improved platform for rapid evaluation of tumor biology and therapeutics.

HIGHLIGHTS

  • Orthotopic injection of genetically defined fallopian tube organoids yield HGSOC.
  • Ovarian tumors with different genotypes evoke distinct immune microenvironments
  • Combining Gemcitabine, anti-PD-L1, and anti-CTLA-4 result in complete responses in Tp53-/-;Ccne1OE;Akt2OE;KrasOE organoid-derived HGSOC
  • Therapeutic response is tumor genotype-specific

Genetically Defined, Syngeneic Organoid Platform for Developing Combination Therapies for Ovarian Cancer
[preprint posted on bioRxiv 2020 Apr 07]

Both fallopian tube and ovarian surface epithelium are cells-of-origin for high-grade serous ovarian carcinoma

The cell-of-origin of high grade serous ovarian carcinoma (HGSOC) remains controversial, with fallopian tube epithelium (FTE) and ovarian surface epithelium (OSE) both considered candidates. Here, by using genetically engineered mouse models and organoids, we assessed the tumor-forming properties of FTE and OSE harboring the same oncogenic abnormalities. Combined RB family inactivation and Tp53 mutation in Pax8+ FTE caused Serous Tubal Intraepithelial Carcinoma (STIC), which metastasized rapidly to the ovarian surface. These events were recapitulated by orthotopic injection of mutant FTE organoids. Engineering the same genetic lesions into Lgr5+ OSE or OSE-derived organoids also caused metastatic HGSOC, although with longer latency and lower penetrance. FTE- and OSE-derived tumors had distinct transcriptomes, and comparative transcriptomics and genomics suggest that human HGSOC arises from both cell types. Finally, FTE- and OSE-derived organoids exhibited differential chemosensitivity. Our results comport with a dualistic origin for HGSOC and suggest that the cell-of-origin might influence therapeutic response.

Both fallopian tube and ovarian surface epithelium are cells-of-origin for high-grade serous ovarian carcinoma Nat Commun 10, 5367 (2019)

SHP2 Inhibition Prevents Adaptive Resistance to MEK Inhibitors in Multiple Cancer Models

The RAS/ERK MAP kinase pathway is aberrantly activated in a large percentage of human cancers, and promotes malignant behavior.  Inhibitors of MEK, one of the key intermediates in this pathway, have had limited utility in the clinic, often due to the rapid development of “intrinsic resistance.”  Intrinsic resistance is due to up regulation of multiple growth factor receptors and their ligands, and previous work by the lab and by others has shown that is required for RAS activation by these receptors.  Here we found that combining MEK and SHP2 inhibitors shows broad efficacy against a wide range of malignancies, and also that SHP2 inhibitors as single agents can antagonize certain types of RAS mutations (fast cycling mutants).

SHP2 Inhibition Prevents Adaptive Resistance to MEK Inhibitors in Multiple Cancer Models.
Cancer Discov. 2018 Oct;8(10):1237-1249.

 

 

Vitamin C in Stem Cell Reprogramming and Cancer

Mutations of one copy of TET2, whose protein product promotes DNA (and RNA) hydroxymethylation (and eventually, DNA and RNA de-methylation, are commonly associated with myelodyspastic syndromes (MDS) and acute myeloid leukemia, among other hematopoietic neoplasms. Previous work had suggested that Vitamin C, an essential co-factor of TET2, can promote TET2 activation as well.  We found that high dose vitamin C, acting via residual TET2 and TET3, had potent anti-neoplastic effects in mouse and human models of MDS/AML. Molecular analysis confirmed that this treatment promotes demethylation of key leukemia-associated genes, including base excision repair genes. The latter result suggested that PARP inhibitors might further increase Vitamin C efficacy, which we also demonstrated.

Vitamin C in Stem Cell Reprogramming and Cancer
Trends Cell Biol. 2018 Sep;28(9):698-708.

 

Functional Genomic Landscape of Human Breast Cancer Drivers, Vulnerabilities, and Resistance

This paper presented the largest (at the time) collection of genome wide shRNA screens of human breast cancer lines, all linked to genomic (mutations, copy number variants, RNAseq, miRNAs) information and RPPA, along with detailed informatics analysis that suggests functional classifications of cancer vulnerabilities.

Functional Genomic Landscape of Human Breast Cancer Drivers, Vulnerabilities, and Resistance
Cell. 2016 Jan 14;164(1-2):293-309.