A patient tumor transplant model of squamous cell cancer identifies PI3K inhibitors as candidate therapeutics in defined molecular bins

Abstract

Targeted therapy development in head and neck squamous cell carcinoma (HNSCC) is challenging given the rarity of activating mutations. Additionally, HNSCC incidence is increasing related to human papillomavirus (HPV). We sought to develop an in vivo model derived from patients reflecting the evolving HNSCC epidemiologic landscape, and use it to identify new therapies. Primary and relapsed tumors from HNSCC patients, both HPV+ and HPV−, were implanted on mice, giving rise to 25 strains. Resulting xenografts were characterized by detecting key mutations, measuring protein expression by IHC and gene expression/pathway analysis by mRNA-sequencing. Drug efficacy studies were run with representative xenografts using the approved drug cetuximab as well as the new PI3K inhibitor PX-866. Tumors maintained their original morphology, genetic profiles and drug susceptibilities through serial passaging. The genetic makeup of these tumors was consistent with known frequencies of TP53, PI3KCA, NOTCH1 and NOTCH2 mutations. Because the EGFR inhibitor cetuximab is a standard HNSCC therapy, we tested its efficacy and observed a wide spectrum of efficacy. Cetuximab-resistant strains had higher PI3K/Akt pathway gene expression and protein activation than cetuximab-sensitive strains. The PI3K inhibitor PX-866 had anti-tumor efficacy in HNSCC models with PIK3CA alterations. Finally, PI3K inhibition was effective in two cases with NOTCH1 inactivating mutations. In summary, we have developed an HNSCC model covering its clinical spectrum whose major genetic alterations and susceptibility to anticancer agents represent contemporary HNSCC. This model enables to prospectively test therapeutic-oriented hypotheses leading to personalized medicine.

Regulation of Head and Neck Squamous Cancer Stem Cells by PI3K and SOX2

“…The University of Colorado Institutional Animal Care and Use Committee approved all experiments involving mice. PDX generation and characterization was previously reported (14). Briefly, tumor pieces were implanted on both flanks of five sixto 10-week-old female Athymic Nude-Foxn1 nu mice (Envigo, Denver, CO).…”

“…Phosphoinositide 3 kinase (PI3K) signaling is commonly activated in HNSCC by PIK3CA amplification or mutation (11)(12)(13); however, antitumor responses to PI3K inhibition can occur with or without these activating genetic events (14)(15)(16). PI3K signaling promotes tumor cell proliferation and survival (17) and is overexpressed in CSCs across different cancers (18,19).…”

Targeting the PI3K/AKT/mTOR pathway in squamous cell carcinoma of the head and neck

“…Activation of the PI3K pathway is also a potential mechanism of resistance to anti-EGFR treatment [21]. Cetuximab-resistant tumors have higher PI3K/AKT pathway gene expression and protein activation compared with cetuximabsensitive tumors [45]. Overcoming resistance to cetuximab may lead to increased response rates and potentially decrease the need for traditional cytotoxic CT in SCCHN.…”

“…Buparlisib has also been shown to enhance the in vitro cytotoxicity of histone deacetylase inhibitors in SCCHN cancer cells and to inhibit tumor growth in xenograft models of SCCHN [49]. PX-866 is another agent that has demonstrated antitumor efficacy in SCCHN models with PIK3CA alterations [45]. Current clinical trials of buparlisib and PX-866 in SCCHN are listed in Table 3.…”

Mer receptor tyrosine kinase is a therapeutic target in pre–B-cell acute lymphoblastic leukemia

“…RNA-seq analysis was performed as previously described 23,24 by using Tophat/Cufflinks workflow. 25 To determine the differentially expressed genes, cuffdiff (with false-discovery rate ,0.001, fold-change .…”