Benhua Xu

Dissecting the Molecular Mechanism of Ionizing Radiation-Induced Tissue Damage in the Feather Follicle

Ionizing radiation (IR) is a common therapeutic agent in cancer therapy. It damages normal tissue and causes side effects including dermatitis and mucositis. Here we use the feather follicle as a model to investigate the mechanism of IR-induced tissue damage, because any perturbation of feather growth will be clearly recorded in its regular yet complex morphology. We find that IR induces defects in feather formation in a dose-dependent manner. No abnormality was observed at 5 Gy. A transient, reversible perturbation of feather growth was induced at 10 Gy, leading to defects in the feather structure. This perturbation became irreversible at 20 Gy. Molecular and cellular analysis revealed P53 activation, DNA damage and repair, cell cycle arrest and apoptosis in the pathobiology. IR also induces patterning defects in feather formation, with disrupted branching morphogenesis. This perturbation is mediated by cytokine production and Stat1 activation, as manipulation of cytokine levels or ectopic Stat1 over-expression also led to irregular feather branching. Furthermore, AG-490, a chemical inhibitor of Stat1 signaling, can partially rescue IR-induced tissue damage. Our results suggest that the feather follicle could serve as a useful model to address the in vivo impact of the many mechanisms of IR-induced tissue damage.

p53 Is a Direct Transcriptional Repressor of Keratin 17: Lessons from a Rat Model of Radiation Dermatitis

The intermediate filament protein keratin 17 (Krt17) shows highly dynamic and inducible expression in skin physiology and pathology. Because Krt17 exerts physiologically important functions beyond providing structural stability to keratinocytes whereas abnormal Krt17 expression is a key feature of dermatoses such as psoriasis and pachyonychia congenita, the currently unclear regulation of Krt17 expression needs to be better understood. Using a rat model of radiation dermatitis, we report here that Krt17 expression initially is down-regulated but later is strongly up-regulated by ionizing radiation. The early down-regulation correlates with the activation of p53 signaling. Deletion of p53 abolishes the initial down-regulation but not its subsequent up-regulation, suggesting that p53 represses Krt17 transcription. Because previous work reported up-regulation of Krt17 by ultraviolet irradiation, which also activates p53 signaling, the effect of ultraviolet radiation was reexamined. This revealed that the initial down-regulation of Krt17 is conserved, but the up-regulation comes much faster. Chromatin immunoprecipitation analysis in vivo and electromobility shift assay in vitro identified two p53-binding sites in the promoter region of Krt17. Thus, p53 operates as a direct Krt17 repressor, which invites therapeutic targeting in dermatoses characterized by excessive Krt17 expression.

Pilot study of intense neoadjuvant chemoradiotherapy for locally advanced rectal cancer: retrospective review of a phase II study

AIMS AND BACKGROUND Locally advanced rectal adenocarcinoma is typically treated with neoadjuvant chemoradiotherapy and surgery. We assessed the effect of an additional cycle of capecitabine/oxaliplatin chemotherapy before surgery in 57 patients with T3/4, N+/- or T1/2, N+ rectal cancer. MATERIALS AND STUDY DESIGN: Radiotherapy (total dose, 50.4 Gy) was combined with three cycles of chemotherapy (two cycles concomitant with radiotherapy), and each cycle consisted of oxaliplatin (130 mg/m2 on day 1) and capecitabine (825 mg/m2, twice per day from day 1 to day 14) for 21 days. In addition to assessing the safety of this treatment, the primary endpoint was pathological complete response (pCR). The secondary endpoint was the change in primary tumor and node stage from pre-treatment to post-surgery. RESULTS Eleven patients (19%) experienced complete tumor regression and 23 patients (40%) experienced tumor regression grade 3. Tumor down-staging occurred in 31 patients (54.4%) and down-staging of nodes occurred in 25 patients (43.9%). There was a significant difference in tumor stage between pre-treatment and post-surgery (P <0.001). Patients with less advanced N stages had significantly better recurrence-free survival but similar metastasis-free survival and overall survival. Tumor regression grade was not associated with overall survival, recurrence-free survival or metastasis-free survival. The most common adverse events were pulmonary infection (n = 6, 10.5%) and intestinal obstruction (n = 6, 10.5%): CONCLUSIONS. An additional cycle of chemotherapy given after chemoradiotherapy and before surgery provided good efficacy and had a satisfactory safety profile in patients with locally advanced rectal cancer.

Neoadjuvant chemotherapy may not benefit esophageal squamous cell carcinoma patients treated with definitive chemoradiotherapy

Background To assess the efficacy of neoadjuvant chemotherapy (NAC) in esophageal squamous cell carcinoma (ESCC) patients treated with definitive chemoradiotherapy (CRT). Methods The clinical data of patients with ESCC treated with chemoradiotherapy with or without NAC were collected and retrospectively reviewed. The overall survival, locoregional failure‐free survival, and distant failure‐free survival were analyzed statistically. Results A total of 60 patients fulfilled the inclusion criteria, of which 41 were treated with NAC‐CRT and 19 were treated with CRT‐alone. Patient characteristics were well balanced between the NAC‐CRT and CRT‐alone groups, except for the ECOG scores. The tumor response to NAC included 11 patients (26.8%) with partial response (PR), 25 patients (61.0%) with stable disease (SD), 5 patients (12.2%) with progression disease (PD), and no patients with complete response (CR). After CRT, 21 patients achieved CR (14 after NAC‐CRT and 7 after CRT‐alone), 30 had PR (19 and 11, respectively), 6 maintained SD (5 and 1, respectively), and 3 patients (all in the NAC‐CRT group) developed PD. Twenty‐nine patients (18 in NAC‐CRT and 11 in CRT‐alone) succumbed to the disease from locoregional or distant failure, one patient in the NAC‐CRT group died of radiation pneumonitis, one patient in the CRT‐alone group died from unknown reasons, and 29 patients remained alive. The overall survival, locoregional failure‐free survival, and distant failure‐free survival at 1 and 2 years in all the patients were 64.9% and 40.5%, 58.6% and 52.0%, and 85.7% and 79.3%, respectively. The overall survival, locoregional failure‐free survival, and distant failure‐free survival between the NAC‐CRT group and the CRT‐alone group were not significantly different. Conclusion In patients with ESCC treated with definitive CRT, NAC treatment using the current regimen does not prolong overall survival, locoregional failure‐free survival or distant failure‐free survival. Further development of NAC treatment is urgently needed.

Ionizing radiation, but not ultraviolet radiation, induces mitotic catastrophe in mouse epidermal keratinocytes with aberrant cell cycle checkpoints

Ultraviolet radiation (UVR) and ionizing radiation (IR) are common genotoxic stresses that damage human skin, although the specific damages to the genomic DNA are different. Here, we show that in the mouse glabrous skin, both UVR and IR induce DNA damage, cell cycle arrest, and condensed cell nuclei. However, only IR induces mitotic catastrophe (MC) in the epidermis. This is because UVR induces a complete blockage of pRB phosphorylation and cell cycle arrest in the G1 phase, whereas pRB phosphorylation remains positive in a significant portion of the epidermal keratinocytes following IR exposure. Furthermore, Cyclin B1 expression is significantly downregulated only by IR but not UVR. Finally, there are more MC cells in the epidermis of p53‐/‐ mice after IR exposure as compared to wild‐type mice. Our results suggest that although both IR and UVR are genotoxic, they show distinct impacts on the cell cycle machinery and thus damage the epidermal keratinocytes via different mechanisms.

Predictive value of carcinoembryonic antigen and carbohydrate antigen 19-9 related to downstaging to stage 0–I after neoadjuvant chemoradiotherapy in locally advanced rectal cancer

Objective To explore the value of carcinoembryonic antigen (CEA) and carbohydrate antigen 19-9 (CA19-9) in predicting downstaging to stage 0–I cancer after neoadjuvant chemoradiotherapy (nCRT) in locally advanced rectal cancer. Materials and methods We respectively investigated pretreatment CEA, pretreatment CA19-9, posttreatment CEA, posttreatment CA19-9, pre–post-CA19-9 ratio, and pre–post-CEA ratio in 674 patients with locally advanced rectal cancer receiving nCRT and determined the patients’ thresholds by using the receiver operating characteristic curve analysis. The association between downstaging (stage 0–I after nCRT), pathological complete response, and clinicopathological parameters was evaluated using the Pearson χ2 test. The clinicopathological parameters which were found to be significantly associated with downstaging were analyzed by logistic regression models and were incorporated into a scoring system. Results Multivariate analysis showed that pretreatment CA19-9 level, posttreatment CEA level, pre–post-CEA ratio, and pre–post-CA19-9 ratio were significantly correlated with downstaging. Area under the curve of the scoring system was higher than that of parameters alone. Conclusion The 4-factor scoring system with CA19-9 level, posttreatment CEA level, pre– post-CEA ratio, and pre–post-CA19-9 ratio is of more value in predicting downstaging to stage 0–I patients with locally advanced rectal cancer after nCRT than using the parameters alone.

Pretreatment Tumor Thickness as a Predictor of Pathologic Complete Response to Neoadjuvant Chemoradiation Therapy for Stage II/III Rectal Adenocarcinoma.

Objectives: To evaluate pretreatment tumor thickness in predicting pathologic complete response (pCR) of stage II/III rectal adenocarcinoma to neoadjuvant chemoradiation (chemoradiotherapy [CRT]). Methods: We retrospectively analyzed 185 patients who were diagnosed with stage II or III rectal adenocarcinoma from January 2011 to July 2013 and treated with neoadjuvant intensity-modulated radiation therapy (45 Gy in 1.8-Gy fractions to pelvis and 50 Gy in 2-Gy fractions to rectal tumor as an integrated boost) or 3 dimensionally conformal radiation therapy (45 Gy in 1.8-Gy fractions to pelvis followed by an additional 5.4-Gy to rectal tumor) concurrently with two 3-week cycles of chemotherapy (oxaliplatin 130 mg/m2 on day 1 and capecitabine 825 mg/m2, twice per day from day 1 to 14, cycle 2 starts on week 4). One week after CRT, 36% patients received 1 more cycle of the above chemotherapy and 55% received 1 to 2 cycles of FOLFOX6. Tumor response was categorized as pCR and non-pCR. Tumor thickness measured on magnetic resonance imaging was collected. A multivariate logistic regression model was used to evaluate the association of potential predictors and pCR. Results: Thirty-eight patients (20.5%) reached pCR. Multivariate analysis found the pretreatment tumor thickness to be associated with higher probability of pCR after adjusting for radiation therapy-surgery interval time and pretreatment carcino-embryonic antigen level. The pretreatment carcino-embryonic antigen level was associated with pCR in the univariate analysis but lost the association in the multivatiate model. The pretreatment T or N stage, tumor volume, distance from tumor to anal verge, craniocaudal length of tumor, radiation therapy technique, and patient age and sex were not associated with pCR. Conclusions: We concluded that pretreatment tumor thickness is an independent predictor for pCR of stage II/III rectal adenocarcinoma to the neoadjuvant CRT.