Laparoscopically assisted diaphragmatic hernia repair with mesh and a myocutaneous flap after left ventricular assist device explantation: A case report.

We report the case of a 32-year-old man who developed a giant diaphragmatic hernia following the removal of a left ventricular assist device 4 years prior due to improved cardiac function. Chest radiography revealed an intrathoracic prolapse of the gastrointestinal tract. The patient was diagnosed with a diaphragmatic hernia and a laparoscopy-assisted repair was performed. A 12 × 8 cm hernia was found intraoperatively on the left diaphragm, and a large portion of the gastrointestinal tract had prolapsed into the thoracic cavity. We attempted to repair the ventromedial defect using mesh; however, it was found to be insufficient. Therefore, we used a left rectus abdominis myocutaneous flap to fill the defect and sutured it to the mesh. A myocutaneous flap could be a useful strategy in cases where complete closure with mesh is difficult.

Measuring serum and drainage fluid interleukin-6 and tumor necrosis factor-α levels for early detection of infectious complications after minimally invasive surgery for gastric cancer.

OBJECTIVE: Interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) are inflammatory cytokines produced in response to biological invasion or infection. Their levels are elevated in the blood and locally. We examined whether measuring IL-6 and TNF-α levels in serum or drainage fluid on postoperative day (POD) 1 could detect infectious complications after minimally invasive surgery for gastric cancer. METHODS: This cohort study included 205 consecutive patients who underwent laparoscopic or robot-assisted gastrectomy for gastric cancer between November 2020 and July 2023. We measured serum and drainage fluid IL-6 and TNF-α levels on POD 1 after gastrectomy. Receiver operating characteristic (ROC) curves were created to compare the diagnostic values of each cytokine and serum C-reactive protein levels for detecting postoperative infectious complications. RESULTS: IL-6 and TNF-α levels in the serum or drainage fluid were significantly higher in patients with an infectious complication. In addition, drainage fluid IL-6 levels were significantly different in patients with versus without intra-abdominal abscess. In the ROC curve analysis, serum and drainage fluid IL-6 had the highest AUC values for any infectious complication and intra-abdominal abscess, respectively. POD 1 serum IL-6 level above 47 pg/mL could detect any infectious complication with sensitivity of 74.1 % and specificity of 71.8 %. POD 1 drainage fluid IL-6 level above 14,750 pg/mL had 100 % sensitivity for detecting intra-abdominal abscess with specificity of 56.0 %. CONCLUSIONS: Measurement of IL-6 levels in blood and drainage fluid on POD 1 is valuable for early detection of postoperative infectious complications or intra-abdominal abscess after gastric cancer surgery.

Prognostic impact of aberrant right hepatic artery involvement in patients with pancreatic cancer: A multicenter retrospective cohort study.

BACKGROUND AND OBJECTIVES: This study aimed to evaluate the prognostic value of aberrant right hepatic artery (A-RHA) involvement in patients with pancreatic cancer (PC). METHODS: This study enrolled 474 patients who underwent upfront pancreatectomy or neoadjuvant treatment for resectable (R) or borderline resectable (BR) PC from four institutions. The patients were divided into three groups: A-RHA involvement group (n = 12), patients who had sole A-RHA involvement without major arterial involvement; BR-A group (n = 104), patients who had major arterial involvement; R/BR-PV group (n = 358), others. RESULTS: All patients in the A-RHA involvement group underwent margin-negative resection. The median overall survival of the entire cohort in the A-RHA involvement, R/BR-PV, and BR-A groups was 41.2, 33.5, and 25.2 months, respectively. Although survival in the R/BR-PV group was significantly more favorable than that in the BR-A group (p = 0.0003), no significant difference was observed between the A-RHA involvement group and the R/BR-PV (p = 0.7332) and BR-A (p = 0.1485) groups. CONCLUSIONS: The prognosis of patients with PC and sole A-RHA involvement was comparable to that of patients with R/BR-PV.

Postoperative venous thromboembolism after surgery for locally recurrent rectal cancer.

BACKGROUND: Local recurrence is common after curative resections of rectal cancer. Surgical resection is considered a primary curative treatment option for patients with locally recurrent rectal cancer (LRRC). LRRC often requires a combined resection of other organs, especially in the case of posterior recurrence, which requires a combined resection of the sacrum, making the surgery highly invasive. Venous thromboembolism (VTE) is one of the lethal complications in the postoperative period, particularly in the field of pelvic surgery. We found no reports regarding the risks of postoperative VTE in surgery for LRRC, a typical highly invasive procedure in the field of colorectal surgery. This study aims to evaluate the risk of postoperative VTE in surgery for LRRC patients. METHODS: From April 2010 to March 2022, a total of 166 patients underwent surgery for LRRC in the pelvic region at our institutions. Clinicopathological background and VTE incidence were compared retrospectively. RESULTS: Among the 166 patients included in the study, 55 patients (33.1%) needed sacral resection. Pharmacological prophylaxis for prevention of VTE was performed in 121 patients (73.3%), and the incidence of VTE was 9.09% (5/55 patients) among those who underwent surgery for LRRC with sacral resection, while it was 1.8% (2/111 patients) in those without sacral resection. In univariate analysis, the combination with sacral resection was identified as a risk factor for VTE in surgery for LRRC (p = 0.047). CONCLUSIONS: This study demonstrates that surgery for LRRC combined with sacral resection could be a significant risk factor for VTE.

A Case of Transanal Endoscopic Excision for Rectal Tumor Using Surgical Instruments With Multi-jointed Structures.

BACKGROUND/AIM: Transanal endoscopic local excision requires fine operation in a very narrow space in the rectum. We report a case in which the use of surgical instruments with a multi-jointed structure allowed safe resection of a lesion with a stable field of view, resulting in preservation of postoperative function. CASE REPORT: The patient was a 49-year-old man who had a rectal neuroendocrine tumor (NET) (G1) with erosive changes in the lower rectum. Preoperative imaging showed no evidence of surrounding lymph node or distant metastasis; thus, we performed a transanal endoscopic local excision of the tumor. After positioning the patient under general anesthesia and securing the field of view in the intra-rectal cavity, the flexion of the surgical instruments with a multi-jointed structure was used to secure the operating space to not interfere with the camera and the surgeon's right hand. The operating field was developed, and the tumor was incised by stable traction. After the excision, the needle was advanced in the direction of the intestinal axis using the multi-jointed holder, and continuous suturing was performed. The patient has no recurrence without any defecation disorder. CONCLUSION: The use of multi-jointed surgical instruments in transanal endoscopic excision of rectal tumors can provide a stable operative field and preserve postoperative function. The advanced flexibility of these instruments allows precise manipulation in the narrow rectal space, resulting in successful tumor resection with minimal invasiveness and no postoperative complications. These findings suggest that multi-jointed instruments are valuable for enhancing the safety and efficacy of minimally invasive rectal surgery.

Surgical approach for a refractory enterocutaneous fistula by combining laparoscopic surgery and a planned open conversion: a case report.

BACKGROUND: An enterocutaneous fistula (ECF) is defined as an abnormal communication between the gastrointestinal tract and skin. ECFs are rarely encountered in clinical practice, yet are frequently difficult to treat. Few reports exist regarding the surgical techniques for the treatment of an ECF. Therefore, we report a case of refractory ECF with concomitant severe adhesions, in which we performed combined laparoscopic adhesiolysis and planned open conversion. CASE PRESENTATION: A 57-year-old female patient underwent a laparotomy for an ovarian cyst in her 20s. At 46 years, adhesiolysis without bowel resection was performed for adhesive small bowel obstruction (SBO). However, her symptoms did not improve. Eighteen days postoperatively, she underwent a reoperation and jejunostomy. An ECF developed post-reoperation; therefore, stoma closure and radical surgery for the ECF were planned. Due to the severe adhesions, only stoma closure was performed, based on intraoperative assessments. The patient was subsequently referred to our hospital. First, skin care around the fistula was provided during an outpatient visit. Appropriate sizing of the stoma pouch was performed, to improve erosions and ulcers. Thereafter, debridement of the perifistula skin and simple closure of the ECF outlet were attempted; however, the ECF recurred shortly thereafter. After 8 years of regular skin care, with the ECF remaining stable, however, manifesting as symptomatic SBO, she underwent laparoscopic adhesiolysis. This procedure was initiated in the epigastric region, where relatively fewer adhesions were anticipated. Post-open conversion, partial resection of the small intestine at four locations, including the fistula site, was performed. Postoperatively, jejunal edema and peristaltic dysfunction, due to narrowing of the superior mesenteric artery occurred. Regular drainage by percutaneous endoscopic gastrostomy was required. However, she improved and was discharged 3 months post-operatively. Three years post-operatively, the ECF and SBO did not recur. CONCLUSIONS: We reported a case of refractory ECF in which we were able to safely perform surgery, by combining laparoscopic adhesiolysis and a planned open conversion. Therefore, the surgical approach used in this case may be an option for securing a safe surgical field, while avoiding collateral damage.

Japanese living donor liver transplantation criteria for hepatocellular carcinoma: nationwide cohort study.

BACKGROUND: Validating the expanded criteria for living donor liver transplantation for hepatocellular carcinoma using national data is highly significant. The aim of this study was to evaluate the validity of the new Japanese criteria for living donor liver transplantation for hepatocellular carcinoma patients and identify factors associated with a poor prognosis using the Japanese national data set. METHODS: The study population comprised patients who underwent living donor liver transplantation for hepatocellular carcinoma at 37 centres in Japan between 2010 and 2018. In a nationwide survey, the overall survival and recurrence-free survival rates were evaluated based on the new Japanese criteria for applying the 5-5-500 rule when extending the indication beyond the Milan criteria. Prognostic factors within the Japanese criteria were determined using the Cox proportional hazards model. RESULTS: Patients within (485 patients) and beyond (31 patients) the Japanese criteria exhibited 5-year overall survival rates of 81% and 58% and 5-year recurrence-free survival rates of 77% and 48% respectively. Patients who met the Milan criteria, but not the 5-5-500 rule, had poorer outcomes. Multivariate analysis for 474 patients identified a neutrophil-to-lymphocyte ratio greater than or equal to 5 and a history of hepatectomy as independent risk factors. CONCLUSION: This nationwide survey confirms the validity of the Japanese criteria. The poor prognostic factors within the Japanese criteria include a neutrophil-to-lymphocyte ratio greater than or equal to 5 and previous hepatectomy.

Organ-specific variations in tumor marker dynamics in postoperative pancreatic cancer recurrence: Trends in lung and liver recurrence highlighting biological heterogeneity.

BACKGROUND/OBJECTIVES: Although tumor recurrence after surgical resection in pancreatic cancer (PC) is generally considered incurable, it is well-accepted that clinical presentations and outcomes vary according to the recurrent sites (e.g., liver vs. lung recurrence), suggesting a possible biological inhomogeneity of PC recurrence. Understanding the behavior of biological factors, specifically tumor markers (TMs), at different recurrence sites may contribute to individualized treatment strategies. Therefore, this study aimed to compare the dynamics of pre-recurrence TMs at liver and lung recurrence sites. METHODS: Patients with isolated postoperative liver or lung recurrence as their first recurrence were enrolled. Starting from the recurrence date confirmed by imaging examinations, the values of TMs (carbohydrate antigen 19-9: CA19-9; carcinoembryonic antigen: CEA) were retrospectively evaluated 6 and 3 months before recurrence and at the time of recurrence. RESULTS: Patients with liver recurrence displayed a significant increase in CA19-9 and CEA levels from as early as 6 months before recurrence. Contrastingly, patients with lung recurrence demonstrated a significant elevation of CA19-9 levels starting from 3 months before recurrence, with no increase in CEA levels, even at the time of recurrence. The relative change in CA19-9 and CEA levels during each period were significantly lower in patients with lung recurrence. CONCLUSIONS: Both TMs exhibited organ-specific variations in patients with postoperative PC recurrence. This disparity may reflect the biological heterogeneity of PC between recurrence patterns, thereby highlighting the importance of conducting postoperative follow-up with consideration of this fact.

Pimitespib, a Novel Heat Shock Protein 90 Inhibitor, Is Effective in Treating Renal Cell Carcinoma by Anti-angiogenetic Signaling.

BACKGROUND/AIM: Most clear cell renal cell carcinomas (ccRCCs) have a dysfunctional von Hippel-Lindau tumor suppressor protein (VHL). Hypoxia-inducible factors 1 and 2 alpha (HIF1α and HIF2α) accumulate in ccRCC with dysfunctional VHL and up-regulate the vascular endothelial growth factor (VEGF) pathway and tumor angiogenesis. Recently, pimitespib (PIM), a potent ATP-competitive inhibitor of heat shock protein 90 (HSP90), was developed. PIM down-regulates the expression of HIF, a key protein in ccRCC progression, with anti-angiogenic effects. This study aimed to examine the effectiveness of PIM in ccRCC and the underlying mechanisms. MATERIALS AND METHODS: The efficacy and mechanism of PIM against ccRCCs was evaluated using ccRCC cell lines. RESULTS: PIM inhibited the VEGFR pathway by down-regulating VEGFR 2, phosphorylated VEGFR 2, and protein levels in downstream signaling pathways. The growth of ccRCC cell lines was inhibited by PIM. Furthermore, PIM inhibits HIF1α, HIF2α, and VEGF expression, suggesting that PIM may suppress angiogenesis in addition to the VEGFR pathway. CONCLUSION: PIM provides a novel approach for treating ccRCC and holds promise for future clinical strategies. Further in vivo and clinical research is required to elucidate the detailed relationship between the effects of PIM and ccRCC.

Three Molecular Developmental Pathways of Remnant Pancreatic Cancer after Resection: A Nationwide Project Study of Japan Pancreas Society.

OBJECTIVE: This study aimed to clarify the molecular mechanism of remnant pancreatic cancer (PC) development after primary PC resection. SUMMARY BACKGROUND DATA: Molecular mechanisms of the development of remnant PCs following primary PC resection are largely unknown. METHODS: Forty-three patients undergoing remnant PC resection after primary PC resection between 2001 and 2017 at 26 institutes were retrospectively analyzed. Clinicopathological features and molecular alterations detected by targeted amplicon sequencing of 36 PC-associated genes were evaluated. RESULTS: These patients showed significantly lower body mass indices and higher hemoglobin A1c values at remnant PC resection than at primary PC resection. A comparison of the molecular features between primary and remnant PCs indicated that remnant PCs were likely to develop via three different molecular pathways: successional, showing identical and accumulated alterations (n=14); phylogenic, showing identical and distinct alterations (n=26); and distinct, showing independent distinctive alterations (n=3). The similarity of gene alterations was associated with time to the remnant PC development (r=－0.384, P=0.0173). Phylogenic pathways were significantly associated with the intraductal spread of carcinoma (P=0.007). Patient survival did not differ significantly depending on these molecular pathways. CONCLUSION: Molecular profiling uncovered three pathways for the development of remnant PCs, namely, successional, phylogenic, and distinct pathways. The vast majority of remnant PCs are likely to be molecularly associated with primary PCs either in the successional or phylogenic way. This information could impact the design of a strategy for monitoring and treating remnant PCs.

Pancreas-left gastric artery angle predicts difficulty of suprapancreatic lymph node dissection in gastrectomy for gastric cancer: a cross-sectional study.

PURPOSE: Suprapancreatic lymph node dissection is one of the most challenging procedures performed in the treatment of gastric cancer. This study aimed to investigate whether the pancreas-left gastric artery angle (PLA) can be used to predict the difficulty of the procedure. METHODS: This was a single-center cross-sectional study. Before gastrectomy, the patients were classified according to the size of the PLA into the small PLA (s-PLA; < 30°) and large PLA (l-PLA; ≥ 30°) groups in a surgeon-blinded manner. After gastrectomy, a surgeon evaluated suprapancreatic lymph node dissection as hard, normal, or easy to perform. RESULTS: Seventy-three patients were enrolled in the study. Surgeons evaluated lymph node dissection as hard in 43.8 and 8.7% of patients in the s-PLA and l-PLA groups, respectively (p = 0.002). The time taken for suprapancreatic lymph node dissection was also significantly longer in the s-PLA group than in the l-PLA group (p = 0.040). In patients who underwent laparoscopic gastrectomy, the time for node dissection in the s-PLA group was also significantly longer than that in the s-PLA group (p = 0.021), while there was no difference in those who underwent robotic surgery (p = 0.815). CONCLUSION: PLA is useful for predicting the degree of difficulty of suprapancreatic lymph node dissection during gastrectomy for gastric cancer.

Long-Term Effects of Oral Nutritional Supplements After Gastrectomy for Gastric Cancer: A Survival Analysis from a Multicenter, Open-Label, Randomized Controlled Trial.

BACKGROUND: Weight loss (WL) after gastrectomy for gastric cancer is associated with both decreased compliance with adjuvant chemotherapy and impaired survival. This study examined the effects of administering oral nutritional supplements (ONS) for 3 months after gastrectomy in terms of compliance with adjuvant chemotherapy and survival outcomes. METHODS: This large-scale, multicenter, open-label, randomized controlled trial enrolled 1,003 gastric cancer patients undergoing curative gastrectomy. Patients were assigned to the control group (n = 503) or ONS group (n = 500). In the ONS group, 400 kcal/day of ONS was recommended in addition to a regular diet for 3 months after gastrectomy. Compliance with adjuvant chemotherapy and survival outcomes were compared between the two groups. RESULTS: Compared with the control group, the ONS group showed significantly decreased WL at 3 months after gastrectomy (8.6 ± 6.1 vs. 7.2 ± 5.7%, respectively, P = 0.0004). The control and ONS groups did not differ regarding the induction rate of adjuvant chemotherapy (84.9 vs. 82.8%, respectively, P = 0.614) or the continuation rate at 3 months postoperatively (75.3 vs. 76.6%, respectively, P = 0.809). Oral nutritional supplements for 3 months showed no survival benefit; the 3- and 5-year overall survival (OS) rates were 91.3% and 87.6% in the control group and 89.6% and 86.4% in the ONS group, respectively, indicating no significant difference (P = 0.548). Subgroup analysis could not detect a population in which ONS administration increased OS. CONCLUSIONS: Administration of ONS for 3 months after gastrectomy was not associated with increased compliance with adjuvant chemotherapy or with improved prognosis.

Decreased islet amyloid polypeptide staining in the islets of insulinoma patients.

Islet amyloid polypeptide (IAPP) is a factor that regulates food intake and is secreted from both pancreatic islets and insulinoma cells. Here, we aimed to evaluate IAPP immunohistochemically in islets or insulinoma cells in association with clinical characteristics. We recruited six insulinoma patients and six body mass index-matched control patients with pancreatic diseases other than insulinoma whose glucose tolerance was confirmed to be normal preoperatively. IAPP and IAPP-insulin double staining were performed on pancreatic surgical specimens. We observed that the IAPP staining level and percentage of IAPP-positive beta cells tended to be lower (p = 0.1699) in the islets of insulinoma patients than in those of control patients, which might represent a novel IAPP expression pattern under persistent hyperinsulinemia and hypoglycemia.

Serum levels of the N-terminal fragment of connective tissue growth factor is a novel biomarker for chronic pancreatitis.

Chronic inflammation of the pancreas is considered to be one of the causes of pancreatic cancer. However, the diagnosis of chronic pancreatitis (CP) is very difficult in the pancreas, where biopsies are difficult to perform. The prevalence of CP is estimated to be many times more common than in patients with actual symptomatic CP. In recent years, abnormal cleavage of certain proteins has attracted attention as a biomarker for CP other than pancreatic enzymes. Connective tissue growth factor (CTGF) is one of the growth factors involved in tissue repair and other processes and is increased by stimulation of transforming growth factor-ß, suggesting a relationship of CTGF with fibrosis. In this study, we measured the total length of CTGF in blood and N-terminal fragment CTGF in 48 cases of chronic pancreatitis, 64 cases of pancreatic cancer and 45 healthy volunteers (HV). Interestingly, we found that blood N-terminal fragment CTGF level was significantly increased in CP and pancreatic cancer patients. Multiple logistic regression analysis showed serum levels of N-terminal fragment CTGF, CRP and amylase were significant and independent variables for the differential diagnosis of CP from HV. Receiver operating characteristic analysis showed that area under the curve (AUC) value of serum N-terminal fragment CTGF level was 0.933, which can differentiate between CP and HV. Several factors would be involved in the increase in serum N-terminal fragment CTGF level. In conclusion, serum N-terminal fragment CTGF level is a promising new biomarker for CP.

Clinical significance of ribosomal protein S15 expression in patients with colorectal cancer liver metastases.

BACKGROUND: Liver metastasis is the most frequently observed distant metastasis of colorectal cancer, and the residual liver recurrence rate after hepatic resection is still high. To explore the mechanism of liver metastasis to discover potential new treatments, we assessed the relationship between the expression of differentially expressed genes (DEGs) and prognosis in patients with colorectal cancer liver metastasis (CRLM). METHODS: The gene expression dataset was extracted from The Cancer Genome Atlas and the Gene Expression Omnibus. Significance analysis of DEGs between tumor and normal samples of colorectum, liver, and lung was conducted. A total of 80 CRLM patients were studied to assess the expression of RPS15, characteristics, and outcomes. We examined the relationships of RPS15 expression to cell viability and apoptosis in vitro and vivo. RESULTS: Significance analysis identified 33 DEGs. In our cohorts, the overall survival rates were significantly lower in the high-RPS15-expression group, and high expression of RPS15 was an independent and unfavorable prognostic factor in recurrence-free survival and overall survival. Knockdown of RPS15 expression reduced the proliferative capacity of colorectal cancer cells and increased BAX-induced apoptotic cell death. CONCLUSIONS: RPS15 expression is an independent prognostic factor for CRLM patients and might be a novel therapeutic target for CRLM.

Significance of signal recognition particle 9 nuclear translocation: Implications for pancreatic cancer prognosis and functionality.

Signal recognition particles (SRPs) are essential for regulating intracellular protein transport and secretion. Patients with tumors with high SRP9 expression tend to have a poorer overall survival. However, to the best of our knowledge, no reports have described the relationship between SRP9 localization and prognosis in pancreatic cancer. Thus, the present study aimed to investigate this relationship. Immunohistochemical staining for SRP9 using excised specimens from pancreatic cancer surgery cases without preoperative chemotherapy or radiotherapy showed that SRP9 was preferentially expressed in the nucleus of the cancerous regions in some cases, which was hardly detected in other cases, indicating that SRP9 was transported to the nucleus in the former cases. To compare the prognosis of patients with SRP9 nuclear translocation, patients were divided into two groups: Those with a nuclear translocation rate of >50% and those with a nuclear translocation rate of ≤50%. The nuclear translocation rate of >50% group had a significantly better recurrence­free survival than the nuclear translocation rate of ≤50% group (P=0.037). Subsequent in vitro experiments were conducted; notably, the nuclear translocation rate of SRP9 was reduced under amino acid­deficient conditions, suggesting that multiple factors are involved in this phenomenon. To further study the function of SRP9 nuclear translocation, in vitro experiments were performed by introducing SRP9 splicing variants (v1 and v2) and their deletion mutants lacking C­terminal regions into MiaPaCa pancreatic cancer cells. The results demonstrated that both splicing variants showed nuclear translocation regardless of the C­terminal deletions, suggesting the role of the N­terminal regions. Given that SRP9 is an RNA­binding protein, the study of RNA immunoprecipitation revealed that signaling pathways involved in cancer progression and protein translation were downregulated in nuclear­translocated v1 and v2. Undoubtedly, further studies of the nuclear translocation of SRP9 will open an avenue to optimize the precise evaluation and therapeutic control of pancreatic cancer.

Tissue-Resident Memory T Cells in Gastrointestinal Cancers: Prognostic Significance and Therapeutic Implications.

Gastrointestinal cancers, which include a variety of esophageal and colorectal malignancies, present a global health challenge and require effective treatment strategies. In the evolving field of cancer immunotherapy, tissue-resident memory T cells (Trm cells) have emerged as important players in the immune response within nonlymphoid tissues. In this review, we summarize the characteristics and functions of Trm cells and discuss their profound implications for patient outcomes in gastrointestinal cancers. Positioned strategically in peripheral tissues, Trm cells have functions beyond immune surveillance, affecting tumor progression, prognosis, and response to immunotherapy. Studies indicate that Trm cells are prognostic markers and correlate positively with enhanced survival. Their presence in the tumor microenvironment has sparked interest in their therapeutic potential, particularly with respect to immune checkpoint inhibitors, which may improve cancer treatment. Understanding how Trm cells work will not only help to prevent cancer spread through effective treatment but will also contribute to disease prevention at early stages as well as vaccine development. The role of Trm cells goes beyond just cancer, and they have potential applications in infectious and autoimmune diseases. This review provides a thorough analysis of Trm cells in gastrointestinal cancers, which may lead to personalized and effective cancer therapies.

BRAF V600E-induced distinct DNA damage response defines the therapeutic potential of p53 activation for TP53 wild-type colorectal cancer.

BRAF V600E, one of the most frequent mutations in the MAPK pathway, confers poor prognosis to colorectal cancers (CRCs), partly because of chemotherapeutic resistance. Oncogene-induced DNA damage responses (DDRs) that primarily activate p53 are important mechanistic barriers to the malignant transformation of cells; however, the mechanism underlying this impairment in cancer remains unknown. Here, we evaluated the responses of BRAFV600E-induced DDRs in two CRC cell lines, SW48 and LIM1215, both of which harbor wild-type TP53, KRAS, and BRAF. BRAFV600E transduction exhibited distinct phenotypes in these cells: SW48 cell proliferation markedly decreased, whereas that of LIM1215 increased. BRAFV600E expression induced the activation of oncogene-induced DDR signaling in SW48 cells, but not in LIM1215 cells, whereas chemotherapeutic agents similarly activated DDRs in both cell lines. Knockdown experiments revealed that these responses in SW48 cells were mediated by p53-p21 pathway activation. Comet assay (both alkaline and neutral) revealed that BRAFV600E increased single-strand breaks to the same extent in both cell lines; however, in case of LIM1215 cells, it only facilitated double-strand breaks. Furthermore, the proliferation of LIM1215 cells, wherein no oncogene-induced DDRs occurred, was synergistically inhibited upon MDM2 inhibitor-mediated p53 activation combined with MEK inhibition. Taken together, these distinct DDR signaling responses highlight the novel characteristics of BRAFV600E-mutated CRC cells and define the therapeutic potential of p53 activation combined with MAPK inhibition against TP53 wild-type CRC harboring a BRAFV600E mutation.