Poly(ADP-Ribose) Polymerase Inhibition Sensitizes Colorectal Cancer-Initiating Cells to Chemotherapy.

Colorectal cancer (CRC) remains a leading killer in the U.S. with resistance to treatment as the largest hurdle to cure. Colorectal cancer-initiating cells (CICs) are a self-renewing tumor population that contribute to tumor relapse. Here, we report that patient-derived CICs display relative chemoresistance compared with differentiated progeny. In contrast, conventional cell lines failed model therapeutic resistance. CICs preferentially repaired chemotherapy-induced DNA breaks, prompting us to interrogate DNA damage pathways against which pharmacologic inhibitors have been developed. We found that CICs critically depended on the key single-strand break repair mediator, poly(ADP-ribose) polymerase (PARP), to survive treatment with standard-of-care chemotherapy. Small molecule PARP inhibitors (PARPi) sensitized CICs to chemotherapy and reduced chemotherapy-treated CIC viability, self-renewal, and DNA damage repair. Although PARPi monotherapy failed to kill CICs, combined PARPi therapy with chemotherapy attenuated tumor growth in vivo. Clinical significance of PARPi for CRC patients was supported by elevated PARP levels in colorectal tumors compared with normal colon, with further increases in metastases. Collectively, our results suggest that PARP inhibition serves as a point of fragility for CICs by augmenting therapeutic efficacy of chemotherapy. Stem Cells 2019;37:42-53.

Prognostic Implications of Pathological Response to Neoadjuvant Chemoradiation in Pathologic Stage III Rectal Cancer.

OBJECTIVE: To evaluate the independent prognostic ability of the American Joint Committee on Cancer (AJCC) tumor regression scores within pathologic stage II and III rectal cancers. BACKGROUND: Response to neoadjuvant chemoradiation (nCRT) has been debated as a biologic surrogate for tumor biology and prognosis in rectal cancer. AJCC regression scores have been shown to correlate with prognosis. METHODS: Patient demographics, tumor characteristics, and AJCC scores (0 = complete response; 1 = isolated tumor cells remaining; 2 = residual cancer outgrown by fibrosis; 3 = extensive residual cancer) were assessed from 545 rectal cancer patients treated by nCRT followed by surgery at a single institution. Patients were classified as responders (score 0-2) or nonresponders (score 3). Survival analyses were performed using Cox proportional hazards models. RESULTS: Of 545 cases, 123 and 182 were pathologic stage II and III, respectively. Median follow-up was 4.9 years. AJCC regression scores were not independently prognostic within stage II cancers. However, AJCC scores were strongly associated with prognosis within stage III cancers (nonresponse 5-year overall survival [OS] 27% vs 67%, P < 0.001). Stage III responders (N = 139, 76.4%) had similar outcomes to stage II (5-year OS 67% vs 74%, P = 0.89). Conversely, stage III nonresponders (N = 43, 23.6%) approached stage IV outcomes (5-year OS 27% vs 18%, P = 0.09). On multivariable analysis, nonresponse (hazard ratio 3.2, 95% confidence interval 1.7-6.2), along with positive margin, abdominoperineal resection, and no adjuvant chemotherapy administration were independently associated with worse OS. CONCLUSIONS: AJCC response score after nCRT is a novel prognostic factor in pathologic stage III rectal cancer and may guide surveillance and adjuvant therapy decisions.

American Joint Committee on Cancer and College of American Pathologists regression grade: a new prognostic factor in rectal cancer.

BACKGROUND: The American Joint Committee on Cancer and the College of American Pathologists provide guidelines for reporting pathologic response to neoadjuvant treatment of rectal cancer. The clinical relevance of these tumor regression grading guidelines is undefined. OBJECTIVE: This study evaluates the prognostic significance of the American Joint Committee on Cancer/College of American Pathologists regression grading. DESIGN: This is a retrospective cohort study based on data from a prospectively maintained colorectal cancer database. The cohorts were defined by American Joint Committee on Cancer/College of American Pathologists tumor regression grade. SETTING: This study was performed at a single tertiary referral center. PATIENTS: Five hundred thirty-eight patients with primary rectal adenocarcinoma who underwent neoadjuvant therapy between 1992 and 2012 were identified. MAIN OUTCOME MEASURES: The primary outcome measures were overall and disease-free survival, cancer-specific mortality, and cumulative recurrence rate. RESULTS: Five hundred thirty-eight patients were included, 105 of whom (19.5%) were American Joint Committee on Cancer/College of American Pathologists grade 0, 153 patients (28.4%) were grade 1, 181 patients (33.6%) were grade 2, and 99 (18.4%) were grade 3. Kaplan-Meier analysis revealed that American Joint Committee on Cancer/College of American Pathologists grade was associated with significant differences in overall survival (p < 0.001), disease-free survival (p < 0.001), and cumulative recurrence (p < 0.001). No local recurrences were observed in American Joint Committee on Cancer/College of American Pathologists grade 0 patients. Five-year overall survival rates were 89%, 74%, 63%, and 40% (p < 0.001); 5-year disease-free survival rates were 85%, 64%, 54%, and 33% (p < 0.001); and 5-year recurrence rates were 7%, 18%, 25%, and 33% (p <0.001) for American Joint Committee on Cancer/College of American Pathologists grades 0, 1, 2, and 3. After adjusting for significant covariates, including pathologic stage, American Joint Committee on Cancer/College of American Pathologists grade remained an independent predictor of overall survival (p < 0.001), disease-free survival (p < 0.001), and cumulative recurrence (p < 0.001) in Cox regression analyses. LIMITATIONS: This was a retrospective study. There was a low local recurrence rate in our population, limiting the sensitivity of recurrence analyses. CONCLUSIONS: This is the first study to delineate American Joint Committee on Cancer/College of American Pathologists regression grade as an independent oncologic prognostic factor. This information can be used in discussions with patients who have rectal cancer.

Clinical criteria underestimate complete pathological response in rectal cancer treated with neoadjuvant chemoradiotherapy.

BACKGROUND: Published criteria define specific mucosal features of clinical complete response for rectal cancer after neoadjuvant chemoradiotherapy. OBJECTIVE: The aim of this study was to determine the performance of these criteria to identify a pathological complete response. DESIGN: Histopathology reports were retrieved for consecutive rectal cancers treated with neoadjuvant therapy followed by proctectomy. The mucosal appearance of residual disease was compared with the final pathological stage. SETTING: This study was conducted at a single-institution, tertiary referral center. PATIENTS: The study included 238 patients. INTERVENTIONS: All patients underwent neoadjuvant chemoradiation followed by proctectomy between 1997 and 2007. MAIN OUTCOME MEASURES: Gross mucosal appearance was compared with the final pathological stage. RESULTS: Following neoadjuvant chemoradiation, 61 of 238 (25%) patients were downstaged to ypT0. Forty-five of these 61 patients (74%) had a residual mucosal abnormality that precluded assignment of a complete response. Of these, 40 had residual ulcers (up to 10 mm in depth) and 5 had exophytic lesions. The remaining 16 patients with pathological complete response fulfilled criteria for clinical complete response and had either no visible abnormality or a scar. Although mucosal complete clinical response was statistically associated with ypT0 status (p < 0.0001), 6 of 22 (27%) patients with mucosal complete clinical response still had residual disease. Smaller size of residual mucosal abnormality was also associated with ypT0 status (p = 0.002). LIMITATIONS: This is a retrospective study and preoperative clinical assessment of response is not recorded for comparison to resected specimens. CONCLUSIONS: The majority of patients attaining ypT0 status do not display mucosal features of complete response. When present, a mucosal complete response is statistically associated with ypT0 status, but is poorly sensitive. If rectal conservation after chemoradiation is to be pursued, alternative means of restaging are required to maximize the number who might benefit from this approach.

Statin therapy is associated with improved pathologic response to neoadjuvant chemoradiation in rectal cancer.

BACKGROUND: Achieving a pathologic complete response to neoadjuvant chemoradiation improves prognosis in rectal cancer. Statin therapy has been shown to enhance the impact of treatment in several malignancies, but little is known regarding the impact on rectal cancer response to neoadjuvant chemoradiation. OBJECTIVE: The purpose of this study was to determine whether statin use during neoadjuvant chemoradiation improves pathologic response in rectal cancer. DESIGN: This was a retrospective cohort study based on data from a prospectively maintained colorectal cancer database. The 2 cohorts were defined by statin use during neoadjuvant chemoradiation. SETTING: This study was performed at a single tertiary referral center. PATIENTS: Four hundred seven patients with primary rectal adenocarcinoma who underwent neoadjuvant therapy then proctectomy between 2000 and 2012 were included. Ninety-nine patients (24.3%) took a statin throughout the entire course of neoadjuvant therapy. MAIN OUTCOME MEASURES: The primary outcome measure was pathologic response to neoadjuvant chemoradiotherapy as defined by the American Joint Committee on Cancer tumor regression grading system, grades 0 to 3. RESULTS: Patients in the statin cohort had a lower median regression grade (1 vs 2, p = 0.01) and were more likely to have a better response (grades 0-1 vs 2-3) than those not taking a statin (65.7% vs 48.7%, p = 0.004). Statin use remained a significant predictor of an American Joint Committee on Cancer grade 0 to 1 (OR, 2.25; 95% CI, 1.33-3.82) in multivariate analyses. Although statin use itself did not significantly improve oncologic outcomes, an American Joint Committee on Cancer grade 0 to 1 response was associated with statistically significant improvements in overall survival, disease-free survival, cancer-specific mortality, and local recurrence. LIMITATIONS: This was a retrospective study and subject to nonrandomization of patients and incorporated patients on variable statin agents and doses. CONCLUSIONS: Statin therapy is associated with an improved response of rectal cancer to neoadjuvant chemoradiation. These data provide the foundation for a prospective clinical trial.

Recent advancements in the minimally invasive management of esophageal perforation, leaks, and fistulae.

INTRODUCTION: Historically, the gold standard management of esophageal perforations, leaks, and fistulae has been traditional open surgery, but it is associated with significant morbidity and mortality. Minimally invasive approaches offer alternatives to surgery in treating hemodynamically stable patients with such defects. In this review article, we will discuss the recent advancements in the minimally invasive management of esophageal perforations, leaks, and fistulas. AREAS COVERED: This review includes information from case reports, case series, and clinical trials on minimally invasive management of esophageal perforations, leaks, and fistulas. The focus is on the devices, outcomes, and application of the technology. EXPERT COMMENTARY: Minimally invasive treatment represents significant progress in the management of esophageal perforations, leaks, and fistulas. Based on current evidence, it seems safe and effective but it is evolving and more studies are needed to help draw definitive conclusions.

Chemotherapy activates cancer-associated fibroblasts to maintain colorectal cancer-initiating cells by IL-17A.

Many solid cancers display cellular hierarchies with self-renewing, tumorigenic stemlike cells, or cancer-initiating cells (CICs) at the apex. Whereas CICs often exhibit relative resistance to conventional cancer therapies, they also receive critical maintenance cues from supportive stromal elements that also respond to cytotoxic therapies. To interrogate the interplay between chemotherapy and CICs, we investigated cellular heterogeneity in human colorectal cancers. Colorectal CICs were resistant to conventional chemotherapy in cell-autonomous assays, but CIC chemoresistance was also increased by cancer-associated fibroblasts (CAFs). Comparative analysis of matched colorectal cancer specimens from patients before and after cytotoxic treatment revealed a significant increase in CAFs. Chemotherapy-treated human CAFs promoted CIC self-renewal and in vivo tumor growth associated with increased secretion of specific cytokines and chemokines, including interleukin-17A (IL-17A). Exogenous IL-17A increased CIC self-renewal and invasion, and targeting IL-17A signaling impaired CIC growth. Notably, IL-17A was overexpressed by colorectal CAFs in response to chemotherapy with expression validated directly in patient-derived specimens without culture. These data suggest that chemotherapy induces remodeling of the tumor microenvironment to support the tumor cellular hierarchy through secreted factors. Incorporating simultaneous disruption of CIC mechanisms and interplay with the tumor microenvironment could optimize therapeutic targeting of cancer.