The role of adjuvant radiation therapy in the treatment of colorectal cancer

Circ-ACAP2 facilitates the progression of colorectal cancer through mediating miR-143-3p/FZD4 axis

BACKGROUND

Circular RNAs (circRNAs) play crucial roles in multiple cancers, including colorectal cancer (CRC). Here, we explored the role of circRNA ArfGAP with coiled-coil, ankyrin repeat and PH domains 2 (circ-ACAP2) in the progression and radioresistance of CRC.

METHODS

Quantitative real-time polymerase chain reaction (qPCR) and Western blot assay were used to detect RNA and protein expression, respectively. The proliferation, apoptosis, migration, invasion and radioresistance of CRC cells were determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, flow cytometry, transwell migration assay, transwell invasion assay and colony formation assay. The target interaction between microRNA-143-3p (miR-143-3p) and circ-ACAP2 or frizzled class receptor 4 (FZD4) was verified by dual-luciferase reporter assay. Murine xenograft model was established to explore the role of circ-ACAP2 in vivo.

RESULTS

The expression of circ-ACAP2 was prominently enhanced in CRC tissues and cell lines. Circ-ACAP2 facilitated the proliferation, migration, invasion and radioresistance whereas inhibited the apoptosis of CRC cells. MiR-143-3p was a direct target of circ-ACAP2 in CRC cells. Circ-ACAP2 promoted the progression and radioresistance of CRC partly by sponging miR-143-3p. MiR-143-3p interacted with the 3' untranslated region (3'UTR) of FZD4 in CRC cells, and FZD4 overexpression partly reversed miR-143-3p-mediated effects in CRC cells. Wnt/β-catenin signalling was modulated by circ-ACAP2/miR-143-3p/FZD4 axis in CRC cells.

CONCLUSION

Circ-ACAP2 contributed to the development and radioresistance of CRC partly through targeting miR-143-3p/FZD4 axis, which provided novel potential diagnostic and therapeutic targets for CRC.

Raltitrexed: current clinical status and future directions

Raltitrexed ('Tomudex') monotherapy is a conveniently administered alternative to 5-fluorouracil (5-FU) in the first-line treatment of advanced colorectal cancer (CRC), and has single-agent activity in a variety of advanced solid tumours. Although both raltitrexed and 5-FU are thymidylate synthase inhibitors, raltitrexed has a specific mode of action and a toxicity profile distinct from 5-FU. The mechanism of action of raltitrexed is also completely different from that of oxaliplatin, irinotecan and other drugs with which it has been combined. These properties, together with preclinical data, suggested that combinations of raltitrexed with 5-FU, other chemotherapeutic agents, or radiotherapy could result in improved therapies for a variety of advanced solid tumours, including advanced CRC. This review outlines the appropriate management of patients treated with raltitrexed, whether as monotherapy or in combination, and discusses the preliminary results of combination studies with raltitrexed in a range of tumour types including advanced CRC, malignant mesothelioma, gastric, pancreatic, head and neck, and non-small-cell lung cancers. Of particular interest is the combination of raltitrexed and oxaliplatin, which has shown promising antitumour effects in first-line treatment of advanced CRC and malignant mesothelioma, a disease that is refractory to chemotherapy.

Cancer Chemotherapy Update: Protracted Venous Infusion Fluorouracil for Advanced Colorectal Cancer

The increasing complexity of cancer chemotherapy makes it mandatory that pharmacists be familiar with these highly toxic agents. This column reviews various issues related to the preparation, dispensing, and administration of cancer chemotherapy, both commercially available and investigational.

Current status of total mesorectal excision and autonomic nerve preservation in rectal cancer

Two decades have passed since the late 1970s, which witnessed the introduction of total mesorectal excision (TME)-based operations for rectal cancers on both sides of the Atlantic. Since the introduction of TME, clinical experience has been reported widely in the form of single- and multisurgeon reports from wide geographic regions with multiple participants, and from specialty services with narrow focus and high levels of expertise. All of these published results conclude that in comparison with conventionally practiced blunt surgery for rectal cancer, TME-based (i.e., anatomically correct, sharply performed) operations are associated with significantly lower rates of pelvic (local) recurrences, a significantly higher rate of survival, and significantly lower long-term morbidity. The latter is accomplished through dramatically higher rates of sphincter preservation, and the preservation of both sexual and urinary functions. Overall, there is a remarkable similarity in the clinical results that have been reported from diverse centers. TME now forms the basis of large randomized clinical trials in which the role of adjuvant therapy is being reexamined. The current status of TME is reviewed, and the authors' clinical results of a consecutive series of 544 TME-based operations performed through 1998 are updated.

Investigation of the comparative toxicity of 5-FU bolus versus 5-FU continuous infusion circadian chemotherapy with concurrent radiation therapy in locally advanced rectal cancer

PURPOSE

To compare the relative toxicities of bolus versus infusional 5-FU chemotherapy administrated concurrently during external beam irradiation in patients with locally advanced rectal cancer following surgical extirpation.

METHODS

A total of 26 eligible patients were retrospectively identified as having been treated for rectal adenocarcinoma at the Stratton VAMC between 1989 and 1997. A comparative analysis of treatment dose intensities, treatment delays and toxicities in these patients was performed.

RESULTS

Significantly less WBC toxicity was observed in the patients receiving infusional 5-FU chemotherapy. The other toxicities, with the exception of skin toxicity, were generally less frequent in the 5-FU infusional group. When the toxicities were corrected for 5-FU dose intensity, to yield toxicity per mg of 5-FU, statistically significant differences were found for hematological toxicity (WBC and platelets), and for gastrointestinal toxicity (frequency and severity of diarrhea and weight loss). The majority of patients receiving infusional 5-FU therapy were treated using a circadian pattern of treatment peaking around the time of the radiation therapy. Patients receiving infusional 5-FU were able to tolerate over twice the dose intensity as those receiving bolus administration. Local recurrence rate in all patients was 3.8% comparing favorably to other reported studies. Distant recurrence frequency was also acceptable at 34.6% for the group.

CONCLUSION

Infusional 5-FU chemotherapy compared with bolus therapy during pelvic radiation minimizes toxicity to the patient while maximizing the dose of 5-FU that can be delivered. As infusional 5-FU therapy during radiation has previously been shown to increase disease free duration and survival, infusional 5-FU should be considered as an acceptable standard of care to prevent local recurrence of rectal adenocarcinoma following its resection. Shaping this infusional 5-FU chemotherapy within the day so that most of the daily dose is delivered around the time of the radiation therapy may further modify the toxic therapeutic ratio of combined modality therapy.

Phase II study of radiochemotherapy with UFT and low-dose oral leucovorin in patients with unresectable rectal cancer

PURPOSE

To determine the activity and evaluate the toxicity of uracil and tegafur in a 4:1 molar concentration (UFT) plus low-dose leucovorin administered concomitantly with pelvic irradiation in patients with unresectable or recurrent rectal cancer.

METHODS AND MATERIALS

Thirty-five patients (22 with primary unresectable tumors and 13 with locally recurrent tumors) were enrolled in the trial. Thirty-five patients were evaluable for toxicity and 32 of these were evaluable for clinical response. Patients received 300 mg/m2/day UFT and 30 mg/day leucovorin on days 8-35 concomitantly with pelvic radiotherapy, to a total dose of 45 Gy.

RESULTS

Eight of the 35 (23%) patients developed Grade 3 diarrhea and were treated with radiotherapy alone after this event. Of the 22 patients with unresectable primary tumors, 17 underwent surgery, and resection was feasible in 15 cases (88%). Of the 32 patients evaluable for clinical response, 4 (13%) had a complete clinical response (CR) and 22 (69%) a partial response (PR). A complete pathologic response was observed in 3 cases (18%) and, a PR in 11 cases (65%).

CONCLUSION

The response rates achieved with this schedule seem comparable to those obtained with 5-FU and radiotherapy. These results warrant further evaluation of this combination in patients with unresectable or locally advanced tumors.

Gene therapy for malignant gliomas

Malignant gliomas are attractive targets for gene therapy because of their relatively well-localized distribution. Several new strategies have been devised that target different aspects of glioma biology. Gene transfer can be used to synthesize chemotherapy drugs that block DNA synthesis within these highly mitotic tumors. New genes can be introduced that restore the functions of mutated tumor suppressor genes or block the molecular pathways needed for tumor angiogenesis. Alternatively, the immune response to these tumors can be augmented by the local production of cytokines. Finally, viruses themselves can be used as tumoricidal agents by designing viruses that selectively replicate and destroy tumor cells. The advantages and limitations of these approaches are discussed in the context of their possible application to the treatment of these highly lethal malignancies.