Gregory Vlacich

Resistance to EGFR-Targeted Therapy: A Family Affair

The EGFR-directed antibody cetuximab has proven, albeit modest, clinical benefit as monotherapy in head and neck and colorectal cancers. In a recent study, Yonesaka et al. uncovered a new mechanism of cetuximab resistance mediated by increased ERBB2 signaling via amplification of ERBB2 or increased levels of the ERBB3/ERBB4 ligand heregulin.

Inducible loss of one Apc allele in Lrig1-expressing progenitor cells results in multiple distal colonic tumors with features of familial adenomatous polyposis

Individuals with familial adenomatous polyposis (FAP) harbor a germline mutation in adenomatous polyposis coli (APC). The major clinical manifestation is development of multiple colonic tumors at a young age due to stochastic loss of the remaining APC allele. Extracolonic features, including periampullary tumors, gastric abnormalities, and congenital hypertrophy of the retinal pigment epithelium, may occur. The objective of this study was to develop a mouse model that simulates these features of FAP. We combined our Lrig1-CreERT2/+ mice with Apcfl/+ mice, eliminated one copy of Apc in leucine-rich repeats and immunoglobulin-like domains protein 1 (Lrig1)-positive (Lrig1(+)) progenitor cells with tamoxifen injection, and monitored tumor formation in the colon by colonoscopy and PET. Initial loss of one Apc allele in Lrig1(+) cells results in a predictable pattern of preneoplastic changes, culminating in multiple distal colonic tumors within 50 days of induction, as well as the extracolonic manifestations of FAP mentioned above. We show that tumor formation can be monitored by noninvasive PET imaging. This inducible stem cell-driven model recapitulates features of FAP and offers a tractable platform on which therapeutic interventions can be monitored over time by colonoscopy and noninvasive imaging.

Dose to the inferior pharyngeal constrictor predicts prolonged gastrostomy tube dependence with concurrent intensity-modulated radiation therapy and chemotherapy for locally-advanced head and neck cancer.

BACKGROUND AND PURPOSE To determine if dose and/or dose-volume parameters to anatomic swallowing structures are predictive of gastrostomy tube (PEG) dependence from chemotherapy-intensity modulated radiotherapy (IMRT) in locally advanced head and neck cancer (LAHNC). METHODS AND MATERIALS A retrospective study was performed on 141 consecutive patients with LAHNC (squamous cell) treated with definitive chemoIMRT with weekly concurrent carboplatin and paclitaxel. Late dysphagia was assessed by length of PEG requirement. Analysis of IMRT dose was retrospectively performed for critical swallowing structures. RESULTS Approximately 62% of patients required PEG, the majority placed during treatment. Mean and median time for PEG was 7.7 and 4.4 months respectively (range 1.4-43.8). Only IMRT dose to the inferior constrictor was significantly associated with length of PEG. Mean dose (of individual mean doses) was 47 Gy for prolonged PEG use versus 41 Gy for PEG ⩽ 12 months. V40 to the inferior constrictor also correlated with PEG >12 months (p = 0.02) with a mean V40 of 48% versus 41% for PEG ⩽ 12 months. CONCLUSIONS IMRT dose to the inferior constrictor correlated with persistent dysphagia requiring prolonged PEG use. Maintaining mean inferior constrictor dose to ⩽ 41 Gy and V40 to ⩽ 41% may help minimize gastrostomy tube dependence.

Outcomes of serial dilation for high-grade radiation-related esophageal strictures in head and neck cancer patients

Dysphagia and esophageal stricture are frequent consequences of treatment for head and neck cancer. This study examines the effectiveness of the anterograde‐retrograde rendezvous procedure and serial dilations in reestablishing esophageal patency to allow return to oral diet and gastrostomy tube removal in a cohort of patients with complete or near‐complete esophageal stricture following nonsurgical cancer treatment.

Intensity-Modulated Radiation Therapy with Concurrent Carboplatin and Paclitaxel for Locally Advanced Head and Neck Cancer: Toxicities and Efficacy

BACKGROUND Intensity-modulated radiation therapy (IMRT) and alternative chemotherapy regimens strive to maintain efficacy while minimizing toxicity in locally advanced head and neck cancer (LAHNC) treatment. Our experience with concurrent IMRT and taxane-based chemotherapy is presented. METHODS A retrospective review of 150 consecutive patients with LAHNC treated with IMRT and concurrent taxane-based chemotherapy with curative intent was performed. The IMRT fractionation regimen consisted of 69.3 Gy to gross disease (2.1 Gy/fraction) and 56.1 Gy to prophylactic nodal sites (1.7 Gy/fraction). Weekly paclitaxel (30 mg/m(2)) and carboplatin (area under the concentration-time curve [AUC], 1) were given concurrently to all patients, and 69% received weekly induction with paclitaxel (60 mg/m(2)) and carboplatin (AUC, 2). RESULTS Over 90% of patients received the prescribed radiation dose. Ninety-six percent completed five or more cycles of concurrent chemotherapy, with similar tolerability for induction chemotherapy. A percutaneous endoscopic gastrostomy (PEG) tube was required in 80 patients, with 10 maintaining PEG use >18 months. Acute grade 4 mucositis and dermatitis developed in 2.0% and 4.0% of patients, respectively. No patient experienced nadir sepsis, grade ≥3 late xerostomia, or significant nephropathy or gastrointestinal toxicity. Median follow-up was 30 months. The 3-year locoregional control rate was 83.2% with disease-free survival and overall survival rates of 78.8% and 76.5%, respectively. CONCLUSION Rates of acute and late toxicities were low, with excellent radiation dose delivery and impressive tumor control at 3 years, suggesting that concurrent carboplatin and paclitaxel with IMRT is a reasonable therapeutic option for the curative treatment of LAHNC.

Lrig1+ gastric isthmal progenitor cells restore normal gastric lineage cells during damage recovery in adult mouse stomach

Objective Lrig1 is a marker of proliferative and quiescent stem cells in the skin and intestine. We examined whether Lrig1-expressing cells are long-lived gastric progenitors in gastric glands in the mouse stomach. We also investigated how the Lrig1-expressing progenitor cells contribute to the regeneration of normal gastric mucosa by lineage commitment to parietal cells after acute gastric injury in mice. Design We performed lineage labelling using Lrig1-CreERT2/+;R26R-YFP/+ (Lrig1/YFP) or R26R-LacZ/+ (Lrig1/LacZ) mice to examine whether the Lrig1-YFP-marked cells are gastric progenitor cells. We studied whether Lrig1-YFP-marked cells give rise to normal gastric lineage cells in damaged mucosa using Lrig1/YFP mice after treatment with DMP-777 to induce acute injury. We also studied Lrig1-CreERT2/CreERT2 (Lrig1 knockout) mice to examine whether the Lrig1 protein is required for regeneration of gastric corpus mucosa after acute injury. Results Lrig1-YFP-marked cells give rise to gastric lineage epithelial cells both in the gastric corpus and antrum, in contrast to published results that Lgr5 only marks progenitor cells within the gastric antrum. Lrig1-YFP-marked cells contribute to replacement of damaged gastric oxyntic glands during the recovery phase after acute oxyntic atrophy in the gastric corpus. Lrig1 null mice recovered normally from acute gastric mucosal injury indicating that Lrig1 protein is not required for lineage differentiation. Lrig1+ isthmal progenitor cells did not contribute to transdifferentiating chief cell lineages after acute oxyntic atrophy. Conclusions Lrig1 marks gastric corpus epithelial progenitor cells capable of repopulating the damaged oxyntic mucosa by differentiating into normal gastric lineage cells in mouse stomach.

Abstract 58: Highly tractable stem cell - driven mouse model of colonic neoplasia with features of familial adenomatous polyposis

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA The ApcMin mouse, which harbors a germline mutation in Apc, is the most widely utilized mouse model of colorectal neoplasia; a major drawback to this model is that the tumors arise mainly in the small intestine. In addition, tumorigenesis occurs randomly within the epithelium, complicating examination of the precise tumor cell-of-origin and local environmental cues that promote tumorigenesis. Given the growing importance of stem cells in tumor initiation, it is desirable to build models that target this population. To this end, it is surprising that elimination of one Apc allele in Lgr5+ stem cells does not result in subsequent loss of heterozygosity (LOH) and tumor formation. We recently reported that Lrig1, a pan-ErbB inhibitor, marks a population of stem cells at the base of colonic crypts. To examine the dynamics of colonic tumor initiation and progression, and to compare our disease model with human patients, we examined tamoxifen-induced Lrig1-CreERT2/+;Apcfl/+ mice where Apc LOH occurs in the Lrig1+ stem cells yielding high-grade lesions, faithfully recapitulating this key genetic event in human colon cancer (CRC) initiation. Colonic lesions grow into the luminal space over the span of 50-100 days and can be visualized by both colonoscopic and FDG-PET non-invasive imaging. This inducible mouse model also harbors extra-colonic features of human Familial Adenomatous Polyposis (FAP), an autosomal dominant variant of CRC caused by germline mutations in APC. With stochastic LOH, affected individuals develop colonic adenomas that invariably progress to CRC and many patients develop peri-ampullary tumors, gastric abnormalities, desmoid and soft tissue tumors, along with characteristic eye findings. To further examine the molecular parallels between the mouse and human colonic tumors, we performed RNA-Seq analysis and validated selected targets with immunofluorescence. Interestingly, a number of genes were found to be differentially regulated in the Lrig1-CreERT2/+;Apcfl/+ colonic tumors compared to ApcMin colonic tumors, despite both models being driven by the Wnt/β-catenin pathway. This model is the closest mimic of FAP to-date and represents a tractable system to test the efficacy of innovative therapeutic interventions whose efficacy can be monitored over time by colonoscopy and non-invasive imaging modalities. Our inducible system also allows a detailed dissection of the pre-neoplastic spatiotemporal events that occur following removal of one Apc allele in the mouse colon. To complement these studies, we are currently examining both Lgr5+ and Lrig1+ stem cell participation in colonic tumor initiation both in vivo and ex vivo at super resolution, using our newly developed Lrig1-Apple and Lrig1-Apple/+;Lgr5-EGFP fluorescent reporter mice. Citation Format: Anne E. Powell, Gregory Vlacich, Zhen-Yang Zhao, Eliot McKinley, Rebekah Karns, Mary Kay Washington, Henry Charles Manning, Bruce Aronow, Robert Coffey. Highly tractable stem cell-driven mouse model of colonic neoplasia with features of familial adenomatous polyposis. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 58. doi:10.1158/1538-7445.AM2014-58