Cancer Cell CD44 Mediates Macrophage/Monocyte-Driven Regulation of Head and Neck Cancer Stem Cells.

Tumor-associated macrophages (TAM) in the tumor microenvironment (TME) cooperate with cancer stem cells (CSC) to maintain stemness. We recently identified cluster of differentiation 44 (CD44) as a surface marker defining head and neck squamous cell carcinoma (HNSCC) CSC. PI3K-4EBP1-SOX2 activation and signaling regulate CSC properties, yet the upstream molecular control of this pathway and the mechanisms underlying cross-talk between TAM and CSC in HNSCC remain largely unknown. Because CD44 is a molecular mediator in the TME, we propose here that TAM-influenced CD44 signaling could mediate stemness via the PI3K-4EBP1-SOX2 pathway, possibly by modulating availability of hyaluronic acid (HA), the main CD44 ligand. HNSCC IHC was used to identify TAM/CSC relationships, and in vitro coculture spheroid models and in vivo mouse models were used to identify the influence of TAMs on CSC function via CD44. Patient HNSCC-derived TAMs were positively and negatively associated with CSC marker expression at noninvasive and invasive edge regions, respectively. TAMs increased availability of HA and increased cancer cell invasion. HA binding to CD44 increased PI3K-4EBP1-SOX2 signaling and the CSC fraction, whereas CD44-VCAM-1 binding promoted invasive signaling by ezrin/PI3K. In vivo, targeting CD44 decreased PI3K-4EBP1-SOX2 signaling, tumor growth, and CSC. TAM depletion in syngeneic and humanized mouse models also diminished growth and CSC numbers. Finally, a CD44 isoform switch regulated epithelial-to-mesenchymal plasticity as standard form of CD44 and CD44v8-10 determined invasive and tumorigenic phenotypes, respectively. We have established a mechanistic link between TAMs and CSCs in HNSCC that is mediated by CD44 intracellular signaling in response to extracellular signals. SIGNIFICANCE: These findings establish a mechanistic link between tumor cell CD44, TAM, and CSC properties at the tumor-stroma interface that can serve as a vital area of focus for target and drug discovery.

Inhibiting Translation Elongation with SVC112 Suppresses Cancer Stem Cells and Inhibits Growth in Head and Neck Squamous Carcinoma.

Cancer stem cells (CSC) drive growth, therapy resistance, and recurrence in head and neck squamous cell carcinoma (HNSCC). Regulation of protein translation is crucial for normal stem cells and CSCs; its inhibition could disrupt stemness properties, but translation inhibitors are limited clinically due to toxicity. SVC112 is a synthetic derivative of bouvardin, a plant-derived translation elongation inhibitor. SVC112 had greater antiproliferative effects on HNSCC cells compared with the FDA-approved translation inhibitor omacetaxine mepesuccinate (HHT). SVC112 preferentially inhibited cancer cells compared with patient-matched cancer-associated fibroblasts, whereas HHT was equally toxic to both. SVC112 reduced sphere formation by cell lines and CSCs. SVC112 alone inhibited the growth of patient-derived xenografts (PDX), and SVC112 combined with radiation resulted in tumor regression in HPV-positive and HPV-negative HNSCC PDXs. Notably, CSC depletion after SVC112 correlated with tumor response. SVC112 preferentially impeded ribosomal processing of mRNAs critical for stress response and decreased CSC-related proteins including Myc and Sox2. SVC112 increased cell-cycle progression delay and slowed DNA repair following radiation, enhancing colony and sphere formation radiation effects. In summary, these data demonstrate that SVC112 suppresses CSC-related proteins, enhances the effects of radiation, and blocks growth of HNSCC PDXs by inhibiting CSCs. SIGNIFICANCE: Inhibiting protein elongation with SVC112 reduces tumor growth in head and neck squamous cell carcinoma and increases the effects of radiation by targeting the cancer stem cell pool.

Leading edge or tumor core: Intratumor cancer stem cell niches in oral cavity squamous cell carcinoma and their association with stem cell function.

OBJECTIVES: To describe differences in cancer stem cell (CSC) presence and behavior associated with their intratumor compartment of origin using a patient-derived xenograft (PDX) model of oral cavity squamous cell carcinoma (OCSCC). MATERIALS AND METHODS: Four HPV-negative OCSCC PDX cases were selected (CUHN004, CUHN013, CUHN096, CUHN111) and the percentage of CSCs (ALDH+CD44high) was measured in the tumor Leading Edge (LE) and Core compartments of each PDX tumor case via fluorescence activated cell sorting (FACS). The fraction of cells in the proliferative phase was measured by Ki-67 labelling index of paraffin embedded tissue. The proliferation and invasion of LE versus Core CSCs were compared using sphere and Matrigel invasion assays, respectively. RESULTS: Both CUHN111 and CUHN004 demonstrate CSC enrichment in their LE compartments while CUHN013 and CUHN096 show no intratumor difference. Cases with LE CSC enrichment demonstrate greater Ki-67 labelling at the LE. CSC proliferative potential, assessed by sphere formation, reveals greater sphere formation in CUHN111 LE CSCs, but no difference between CUHN013 LE and Core CSCs. CUHN111 CSCs do not demonstrate an intratumor difference in invasiveness while CUHN013 LE CSCs are more invasive than Core CSCs. CONCLUSION: A discrete intratumor CSC niche is present in a subset of OCSCC PDX tumors. The CSC functional phenotype with regard to proliferation and invasion is associated with the intratumor compartment of origin of the CSC: LE or Core. These individual functional characteristics appear to be modulated independently of one another and independently of the presence of an intratumor CSC niche.

Wnt signaling dynamics in head and neck squamous cell cancer tumor-stroma interactions.

Wnt pathway activation maintains the cancer stem cell (CSC) phenotype and promotes tumor progression, making it an attractive target for anti-cancer therapy. Wnt signaling at the tumor and tumor microenvironment (TME) front have not been investigated in depth in head and neck squamous cell carcinoma (HNSCC). In a cohort of 48 HNSCCs, increased Wnt signaling, including Wnt genes (AXIN2, LGR6, WISP1) and stem cell factors (RET, SOX5, KIT), were associated with a more advanced clinical stage. Key Wnt pathway proteins were most abundant at the cancer epithelial-stromal boundary. To investigate these observations, we generated three pairs of cancer-cancer associated fibroblast (CAF) cell lines derived from the same HNSCC patients. 3D co-culture of cancer spheres and CAFs mimicked these in vivo interactions, and using these we observed increased expression of Wnt genes (eg, WNT3A, WNT7A, WNT16) in both compartments. Of these Wnt ligands, we found Wnt3a, and less consistently Wnt16, activated Wnt signaling in both cancer cells and CAFs. Wnt activation increased CSC characteristics like sphere formation and invasiveness, which was further regulated by the presence of CAFs. Time lapse microscopy also revealed preferential Wnt activation of cancer cells. Wnt inhibitors, OMP-18R5 and OMP-54F28, significantly reduced growth of HNSCC patient-derived xenografts and suppressed Wnt activation at the tumor epithelial-stromal boundary. Taken together, our findings suggest that Wnt signaling is initiated in cancer cells which then activate CAFs, and in turn perpetuate a paracrine signaling loop. This suggests that targeting Wnt signaling in the TME is essential.

Inter- and intra-tumor heterogeneity of SMAD4 loss in head and neck squamous cell carcinomas.

Reports regarding the frequency of SMAD4 loss in human head and neck squamous cell carcinoma (HNSCC) vary significantly. We have shown that SMAD4 deletion contributes to HNSCC initiation and progression. Therefore, accurately detecting genetic SMAD4 loss is critical to determine prognosis and therapeutic interventions in personalized medicine. We developed a SMAD4 fluorescence in situ hybridization (FISH) assay to identify chromosomal SMAD4 loss at the single cell level of primary HNSCC specimens and patient derived xenograft (PDX) tumors derived from HNSCCs. SMAD4 heterozygous loss was detected in 35% of primary HNSCCs and 41.3% of PDX tumors. Additionally, 4.3% of PDX tumors had SMAD4 homozygous loss. These frequencies of SMAD4 loss were similar to those in The Cancer Genome Atlas (TCGA). However, we identified significant heterogeneities of SMAD4 loss (partial or complete) among cells within each tumor. We also found that aneuploidy (monosomy and polysomy) contributed greatly to how to define chromosomal SMAD4 deletion. Furthermore, in cultured PDX tumors, SMAD4 mutant cells outcompeted SMAD4 wildtype cells, resulting in establishing homogenous SMAD4 mutant HNSCC cell lines with partial or complete genomic SMAD4 loss, suggesting a survival advantage of SMAD4 mutant cells. Taken together, our study reveals inter- and intra-tumor heterogeneities of SMAD4 chromosomal loss in HNSCCs. Further, SMAD4 FISH assay provides a platform for future clinical diagnosis of SMAD4 chromosomal loss that potentially serves as a molecular marker for prognosis and therapeutic intervention in cancer patients.

Salivary Gland Cancer Patient-Derived Xenografts Enable Characterization of Cancer Stem Cells and New Gene Events Associated with Tumor Progression.

Purpose: Salivary gland cancers (SGC) frequently present with distant metastases many years after diagnosis, suggesting a cancer stem cell (CSC) subpopulation that initiates late recurrences; however, current models are limited both in their availability and suitability to characterize these rare cells.Experimental Design: Patient-derived xenografts (PDX) were generated by engrafting patient tissue onto nude mice from one acinic cell carcinoma (AciCC), four adenoid cystic carcinoma (ACC), and three mucoepidermoid carcinoma (MEC) cases, which were derived from successive relapses from the same MEC patient. Patient and PDX samples were analyzed by RNA-seq and Exome-seq. Sphere formation potential and in vivo tumorigenicity was assessed by sorting for Aldefluor (ALDH) activity and CD44-expressing subpopulations.Results: For successive MEC relapses we found a time-dependent increase in CSCs (ALDH+CD44high), increasing from 0.2% to 4.5% (P=0.033), but more importantly we observed an increase in individual CSC sphere formation and tumorigenic potential. A 50% increase in mutational burden was documented in subsequent MEC tumors, and this was associated with increased expression of tumor-promoting genes (MT1E, LGR5, and LEF1), decreased expression of tumor-suppressor genes (CDKN2B, SIK1, and TP53), and higher expression of CSC-related proteins such as SOX2, MYC, and ALDH1A1. Finally, genomic analyses identified a novel NFIB-MTFR2 fusion in an ACC tumor and confirmed previously reported fusions (NTRK3-ETV6 and MYB-NFIB)Conclusions: Sequential MEC PDX models preserved key patient features and enabled the identification of genetic events putatively contributing to increases in both CSC proportion and intrinsic tumorigenicity, which mirrored the patient's clinical course. Clin Cancer Res; 24(12); 2935-43. ©2018 AACR.

Osteochondroma of the convexity: pathologic-neuroimaging correlates of a lesion that mimics high-grade meningioma.

Intracranial chondromas are uncommon benign lesions usually attached to dura and located over the convexity of the skull. Osteochondromas are even rarer and additionally contain a benign bony component. Both lesions are reportedly difficult to distinguish from meningiomas on pre-operative neuroimaging studies, although few detailed pathologic-neuroimaging correlation studies have appeared in the literature, particularly for intracranial osteochondromas. A 33-year-old woman with a 4-year history of headaches presented with recent onset of left-sided muscle spasms and weakness. Two days prior to admission to our hospital, neuroimaging studies had shown a large right convexity mass with unusual multifocal bright signal intensities throughout an otherwise isointense mass. The bright signals were interpreted as showing multifocal hemorrhage and the mass was felt to be a convexity meningioma. However, subsequent catheter angiography characterized the lesion as being avascular. The mass was resected en bloc. Extensive histological sectioning revealed a benign osteochondroma predominantly composed of lobules of hypocellular cartilage. Microdissection of the different components revealed that the multifocal, spicule-like bright foci interpreted as hemorrhage on neuroimaging studies were instead foci of benign bone containing metaplastic bone marrow with trilineage hematopoietic cell populations and adipose tissue. Centrally, the hilum of the lesion contained avascular loose connective tissue. No recent or remote hemorrhage was identified anywhere in the lesion. Rare convexity osteochondromas may be mistaken for high-grade meningiomas on neuroimaging studies; their avascular nature, coupled with their complex signal pattern can serve as clues to the correct pre-operative diagnosis.