Prognostic significance of tumor regression grade after preoperative chemoradiotherapy for rectal cancer

Radiation-induced microRNA-622 causes radioresistance in colorectal cancer cells by down-regulating Rb

The standard treatment for patients with locally advanced rectal cancer is preoperative 5-fluorouracil-based chemoradiotherapy followed by total mesorectal excision. However, tumor response to standard dose radiation varies. In this study, we found that miR-622 was increased significantly in ionizing radiation-treated colorectal cancer (CRC) cells compared to the cells cultured with irradiated medium, and persisted stably in surviving cells treated with continuous low-dose radiation. Overexpression of miR-622 induced the radioresistance in vitro. In addition, miR-622 inhibited Rb expression by directly targeting RB1-3′UTR. Overexpression of Rb reversed miR-622-induced radioresistance in vitro. In response to ionizing radiation, the Rb-E2F1-P/CAF complex activated proapoptotic genes. Importantly, miR-622 was highly expressed in tumors of rectal cancer patients with non-regression after standard dose radiotherapy. In conclusion, miR-622 overexpressing cells are induced or selected by radiotherapy, causing in turn radioresistance and poor response to further therapy. MiR-622 is a potential biomarker of responders for radiotherapy and a potential therapeutic target.

Relationships between SMAD3 expression and preoperative fluoropyrimidine-based chemoradiotherapy response in locally advanced rectal cancer patients

BACKGROUND

SMAD3, which is accumulated in the nucleus, transcriptionally regulates TGF-β target genes, playing a significant role in mediating the activities of TGF-β. In this study, we assessed the roles of TGF-β1, SMAD3, and phosphorylated SMAD3 expressions in patients with locally advanced rectal cancer following preoperative fluoropyrimidine-based chemoradiotherapy.

METHODS

Using immunohistochemistry, we examined TGF-β1, SMAD3, and phosphorylated SMAD3 expressions in pre-chemoradiotherapy cancer tissues from 86 locally advanced rectal cancer patients. After chemoradiotherapy, 64 of 86 (74.4 %) locally advanced rectal cancer patients were classified as responders (pathological tumor regression grades of 2-4).

RESULTS

A multivariate analysis showed that phosphorylated SMAD3 overexpression correlated to poor preoperative chemoradiotherapy responses (P = 0.015; OR 7.218; 95 % CI 1.479-35.229). Furthermore, a poor response (pathological tumor regression grades of 0-1) was an independent predictor of postoperative relapse (P = 0.021; OR 5.452; 95 % CI 1.286-23.113). Additionally, patients with phosphorylated SMAD3 overexpression were found to have a worse disease-free survival (P = 0.023).

CONCLUSIONS

Our data suggested that analyzing pre-chemoradiotherapy tumors for phosphorylated SMAD3 overexpression would assist physicians in identifying locally advanced rectal cancer patients who may have a poor response risk to preoperative fluoropyrimidine-based chemoradiotherapy.

DPYD, TYMS, TYMP, TK1, and TK2 genetic expressions as response markers in locally advanced rectal cancer patients treated with fluoropyrimidine-based chemoradiotherapy

This study is to investigate multiple chemotherapeutic agent- and radiation-related genetic biomarkers in locally advanced rectal cancer (LARC) patients following fluoropyrimidine-based concurrent chemoradiotherapy (CCRT) for response prediction. We initially selected 6 fluoropyrimidine metabolism-related genes (DPYD, ORPT, TYMS, TYMP, TK1, and TK2) and 3 radiotherapy response-related genes (GLUT1, HIF-1α, and HIF-2α) as targets for gene expression identification in 60 LARC cancer specimens. Subsequently, a high-sensitivity weighted enzymatic chip array was designed and constructed to predict responses following CCRT. After CCRT, 39 of 60 (65%) LARC patients were classified as responders (pathological tumor regression grade 2 ~ 4). Using a panel of multiple genetic biomarkers (chip), including DPYD, TYMS, TYMP, TK1, and TK2, at a cutoff value for 3 positive genes, a sensitivity of 89.7% and a specificity of 81% were obtained (AUC: 0.915; 95% CI: 0.840-0.991). Negative chip results were significantly correlated to poor CCRT responses (TRG 0-1) (P = 0.014, hazard ratio: 22.704, 95% CI: 3.055-235.448 in multivariate analysis). Disease-free survival analysis showed significantly better survival rate in patients with positive chip results (P = 0.0001). We suggest that a chip including DPYD, TYMS, TYMP, TK1, and TK2 genes is a potential tool to predict response in LARC following fluoropyrimidine-based CCRT.

Glucose transporter 1 (GLUT1) of anaerobic glycolysis as predictive and prognostic values in neoadjuvant chemoradiotherapy and laparoscopic surgery for locally advanced rectal cancer

PURPOSE

We investigated the relationships between biomarkers related to anaerobic glycolytic metabolism (GLUT1, LDH5, PDK1, and HIF-1α proteins), pathologic response, and prognosis.

METHODS

All stage II and stage III rectal cancer patients had 50.4 Gy (1.8 Gy/day in 28 fractions) over 5.5 weeks, plus 5-fluorouracil (425 mg/m(2)/day) and leucovorin (20 mg/m(2)/day) bolus on days 1 to 5 and 29 to 33, and surgery was performed at 7 to 10 weeks after completion of all therapies. Expression of GLUT1, LDH5, PDK1, and HIF-1α proteins was determined by immunohistochemistry and was assessed in 104 patients with rectal cancer treated with neoadjuvant chemoradiotherapy.

RESULTS

This study included stage II and III rectal cancer patients, and each stage accounted for each 50 % of the total cases. A high expression of GLUT1 protein was associated with a significantly lower rate of ypCR compared with low expression of GLUT1 protein (4.0 % vs. 27.8 %, respectively; p = 0.012). GLUT1 expression was also significantly higher in the poor response group (Grade 0, 1) than in the good response group (Grade 2, 3) (34.0 % vs. 14.8 %, respectively; p = 0.022). In recurrence analysis, the expression of GLUT1 protein demonstrated a significant correlation with time to recurrence, based on a log-rank method (p = 0.016). When analyzed by multiple Cox regression, the positive expression of GLUT1 was the most significant and independent unfavorable prognostic factor (p = 0.004).

CONCLUSIONS

GLUT1 expression is a predictive and prognostic factor for pathologic complete response and recurrence in rectal cancer patients treated with 5-flurouracil and leucovorin neo-adjuvant chemoradiotherapy.