Synchronous Reconstruction of a Total Mandibulectomy Defect With a Single Fibula Osteocutaneous Free Flap.

Osteoradionecrosis (ORN) is a well-known and usually late complication of radiation therapy in the treatment of head and neck cancer. Although the therapy can be life extending, it also produces tissue toxicity in ipsilateral and contralateral tissues in an acute and chronic fashion. In the most severe cases of ORN, such as the one presented in this report, bilateral disease results in the need for total mandibulectomy and creates a tremendous reconstructive challenge. The advent of microvascular surgery and free tissue transfer has caused an evolution of the management protocol for severe ORN cases. This report describes a unique case of total mandibulectomy with synchronous reconstruction using a single vascularized fibula osteocutaneous flap with subsequent dental implant reconstruction and prosthetic rehabilitation.

TORC1 suppression predicts responsiveness to RAF and MEK inhibition in BRAF-mutant melanoma.

RAF and MEK (mitogen-activated or extracellular signal-regulated protein kinase kinase) inhibitors are effective in treating patients with BRAF-mutant melanoma. However, most responses are partial and short-lived, and many patients fail to respond at all. We found that suppression of TORC1 activity in response to RAF or MEK inhibitors, as measured by decreased phosphorylation of ribosomal protein S6 (P-S6), effectively predicted induction of cell death by the inhibitor in BRAF-mutant melanoma cell lines. In resistant melanomas, TORC1 activity was maintained after treatment with RAF or MEK inhibitors, in some cases despite robust suppression of mitogen-activated protein kinase (MAPK) signaling. In in vivo mouse models, suppression of TORC1 after MAPK inhibition was necessary for induction of apoptosis and tumor response. Finally, in paired biopsies obtained from patients with BRAF-mutant melanoma before treatment and after initiation of RAF inhibitor therapy, P-S6 suppression predicted significantly improved progression-free survival. Such a change in P-S6 could be readily monitored in real time by serial fine-needle aspiration biopsies, making quantitation of P-S6 a valuable biomarker to guide treatment in BRAF-mutant melanoma.

RNA sequencing of pancreatic circulating tumour cells implicates WNT signalling in metastasis.

Circulating tumour cells (CTCs) shed into blood from primary cancers include putative precursors that initiate distal metastases. Although these cells are extraordinarily rare, they may identify cellular pathways contributing to the blood-borne dissemination of cancer. Here, we adapted a microfluidic device for efficient capture of CTCs from an endogenous mouse pancreatic cancer model and subjected CTCs to single-molecule RNA sequencing, identifying Wnt2 as a candidate gene enriched in CTCs. Expression of WNT2 in pancreatic cancer cells suppresses anoikis, enhances anchorage-independent sphere formation, and increases metastatic propensity in vivo. This effect is correlated with fibronectin upregulation and suppressed by inhibition of MAP3K7 (also known as TAK1) kinase. In humans, formation of non-adherent tumour spheres by pancreatic cancer cells is associated with upregulation of multiple WNT genes, and pancreatic CTCs revealed enrichment for WNT signalling in 5 out of 11 cases. Thus, molecular analysis of CTCs may identify candidate therapeutic targets to prevent the distal spread of cancer.

Homeobox B9 induces epithelial-to-mesenchymal transition-associated radioresistance by accelerating DNA damage responses.

Homeobox 9 (HOXB9), a nontransforming transcription factor overexpressed in breast cancer, alters tumor cell fate and promotes tumor progression and metastasis. Here we show that HOXB9 confers resistance to ionizing radiation by promoting DNA damage response. In nonirradiated cells, HOXB9 induces spontaneous DNA damage, phosphorylated histone 2AX and p53 binding protein 1 foci, and increases baseline ataxia telangiectasia mutated (ATM) phosphorylation. Upon ionizing radiation, ATM is hyperactivated in HOXB9-expressing cells during the early stages of the double-stranded DNA break (DSB) response, accelerating accumulation of phosphorylated histone 2AX, mediator of DNA-damage checkpoint 1, and p53 binding protein 1, at DSBs and enhances DSB repair. The effect of HOXB9 on the response to ionizing radiation requires the baseline ATM activity before irradiation and epithelial-to-mesenchymal transition induced by TGF-ß, a HOXB9 transcriptional target. Our results reveal the impact of a HOXB9-TGF-ß-ATM axis on checkpoint activation and DNA repair, suggesting that TGF-ß may be a key factor that links tumor microenvironment, tumor cell fate, DNA damage response, and radioresistance in a subset of HOXB9-overexpressing breast tumors.

Isolation of circulating tumor cells using a microvortex-generating herringbone-chip.

Rare circulating tumor cells (CTCs) present in the bloodstream of patients with cancer provide a potentially accessible source for detection, characterization, and monitoring of nonhematological cancers. We previously demonstrated the effectiveness of a microfluidic device, the CTC-Chip, in capturing these epithelial cell adhesion molecule (EpCAM)-expressing cells using antibody-coated microposts. Here, we describe a high-throughput microfluidic mixing device, the herringbone-chip, or "HB-Chip," which provides an enhanced platform for CTC isolation. The HB-Chip design applies passive mixing of blood cells through the generation of microvortices to significantly increase the number of interactions between target CTCs and the antibody-coated chip surface. Efficient cell capture was validated using defined numbers of cancer cells spiked into control blood, and clinical utility was demonstrated in specimens from patients with prostate cancer. CTCs were detected in 14 of 15 (93%) patients with metastatic disease (median = 63 CTCs/mL, mean = 386 ± 238 CTCs/mL), and the tumor-specific TMPRSS2-ERG translocation was readily identified following RNA isolation and RT-PCR analysis. The use of transparent materials allowed for imaging of the captured CTCs using standard clinical histopathological stains, in addition to immunofluorescence-conjugated antibodies. In a subset of patient samples, the low shear design of the HB-Chip revealed microclusters of CTCs, previously unappreciated tumor cell aggregates that may contribute to the hematogenous dissemination of cancer.

A genome-wide screen for microdeletions reveals disruption of polarity complex genes in diverse human cancers.

In a genome-wide screen of 684 cancer cell lines, we identified homozygous intragenic microdeletions involving genes encoding components of the apical-basal cell polarity complexes. Among these, PARD3 is disrupted in cell lines and primary tumors from squamous carcinomas and glioblastomas. Reconstituting PARD3 expression in both cell types restores tight junctions and retards contact-dependent proliferation. Searching specifically for small intragenic microdeletions using high-resolution genomic arrays may be complementary to other genomic deletion screens and resequencing efforts in identifying new tumor suppressor genes.