Background/Objectives: Colorectal cancer (CRC) remains a leading cause of cancer mortality globally, with KRAS mutations occurring in 30–40% of cases, contributing to poor prognosis and resistance to anti-EGFR therapy. This review explores the biological significance, clinical implications, and therapeutic targeting of KRAS mutations in CRC. Methods: A comprehensive analysis of the existing literature and clinical trials was performed, highlighting the role of KRAS mutations in CRC pathogenesis, their impact on prognosis, and recent advancements in targeted therapies. Specific attention was given to emerging therapeutic strategies and resistance mechanisms. Results: KRAS mutations drive tumor progression through persistent activation of MAPK/ERK and PI3K/AKT signaling pathways. These mutations influence the tumor microenvironment, cancer stem cell formation, macropinocytosis, and cell competition. KRAS-mutant CRC exhibits poor responsiveness to anti-EGFR monoclonal antibodies and demonstrates primary and acquired resistance to KRAS inhibitors. Recent breakthroughs include the development of KRAS G12C inhibitors (sotorasib and adagrasib) and promising agents targeting G12D mutations. However, response rates in CRC remain suboptimal compared to other cancers, necessitating combination therapies and novel approaches, such as vaccines, nucleic acid-based therapeutics, and macropinocytosis inhibitors. Conclusions: KRAS mutations are central to CRC pathogenesis and present a significant therapeutic challenge. Advances in KRAS-targeted therapies offer hope for improved outcomes, but resistance mechanisms and organ-specific differences limit efficacy. Continued efforts in personalized treatment strategies and translational research are critical for overcoming these challenges and improving patient survival.

Given that cancer stem cells (CSC) play a key role in drug resistance and relapse, targeting CSCs remains promising in cancer therapy. Here we show that RAB5/7, which are involved in the endolysosomal pathway, play key roles in the maintenance of CSC survival via regulation of the mitophagic pathway. Inhibition of RAB5/7 efficiently eliminated colorectal CSCs and disrupted cancer foci. In addition, we identified mefloquine hydrochloride, an antimalarial drug, as a novel RAB5/7 inhibitor and promising colorectal CSC-targeting drug. Endolysosomal RAB5/7 and LAMP1/2 mediated parkin-dependent mitochondrial clearance and modulated mitophagy through lysosomal dynamics. In a patient-derived xenograft (PDX) model of colon cancer, treatment with mefloquine resulted in suppression of mitophagic PINK1/PARKIN and increased mitochondrial disorder and mitochondria-induced apoptosis without apparent side effects. These results suggest that the combination of mefloquine with chemotherapeutic agents in the PDX model potentially disrupts the hierarchy of colorectal cancer cells and identify endolysosomal RAB5/7 and LAMP1/2 as promising therapeutic targets in CSCs. Significance: These findings show that endosomal/lysosomal RAB5 and RAB7, which regulate mitophagy, are essential for the survival of colon cancer stem cells.

Purpose High-output syndrome (HOS) is a complication of ileostomy, which can affect quality of life significantly; however, its exact cause remains unknown. The aim of this study was to establish the frequency, as well as the preoperative and intraoperative factors predictive of HOS. Methods The subjects of this study were 164 consecutive patients who underwent colorectal cancer surgery with ileostomy construction at our institute between January, 2011 and August, 2018. Thirteen patients with postoperative complications reported as causes of HOS, including intraperitoneal abscess, paralytic ileus, and outlet obstruction, were excluded. We used a logistic regression analysis to identify the factors predictive of HOS. Results HOS developed in 36 of the 151 patients (23.8%). There were significantly more diabetic patients in the HOS group (P = 0.03), but other patient factors such as age, gender, body mass index, and use of daily laxatives were not significantly different between the groups. The HOS group had significantly more cases of total proctocolectomy (P = 0.04), but other surgical factors such as operative time, and blood transfusion were not significantly different between the two groups. Conclusions These results indicate that diabetes and total proctocolectomy are preoperative predictors of HOS, allowing for the possibility of early intervention via post-surgical treatment.

The safety of single-incision laparoscopic surgery (SLS) in elderly patients with colorectal cancer has not been established. The aim of the current study was to compare the outcomes of SLS and multi-port laparoscopic surgery (MLS) and to assess the feasibility of SLS in colorectal cancer patients aged ≥70 years. A retrospective case-control study of colon cancer patients undergoing elective surgical intervention between 2011 and 2014 was conducted. A total of 129 patients with colon cancer underwent surgery and were included in the analysis. Data regarding patient demographics, surgical variables, oncological outcomes and short-term outcomes were evaluated for statistical significance to compare MLS (n=79) and SLS (n=50) in colon cancer patients. No significant differences were observed in patient characteristics. No case required re-admission within 30 days post surgery. The mean surgery times were similar for the MLS and SLS groups when cases with left and right hemicolectomies were combined (207.7 and 215.9 min, respectively; P=0.47). In addition, overall perioperative outcomes, including blood loss, number of lymph nodes harvested, size of the surgical margin and complications, were similar between these groups. Thus, we suggest that SLS can be performed safely in elderly patients with colon cancer.

Background: Sarcopenia, the age-related loss of muscle mass, is a negative prognostic factor in gastrointestinal cancer. Sarcopenia combined with visceral obesity (sarcopenic obesity) is associated with poor outcomes. We explored the influence of obesity and other factors on the prognosis of patients with colorectal cancer diagnosed with sarcopenia. Methods: We enrolled 211 patients with colorectal cancer diagnosed with preoperative sarcopenic obesity who underwent radical resection at Osaka University Hospital between January 2009 and January 2012. Muscle mass was assessed using the psoas muscle mass index. Obesity was evaluated by measuring the visceral fat area in the umbilical region. Patients were categorized into two groups: sarcopenia with obesity (SO) and sarcopenia without obesity (non-SO). Overall survival, cancer-specific survival, and cancer-related relapse-free survival (CRRFS) were compared between the two groups. Patient characteristics, including age, sex, body mass index, serum albumin, C-reactive protein, tumor markers, prognostic nutritional index (PNI), modified Glasgow prognostic score (mGPS), and geriatric nutritional risk index (GNRI), were also analyzed. Results: CRRFS was significantly shorter in the SO group than in the non-SO group (p = 0.028). PNI, mGPS, and GNRI were not identified as significant prognostic factors for CRRFS. Multivariate analysis highlighted sarcopenic obesity, elevated carcinoembryonic antigen levels, and unfavorable histological types as significant predictors of poor CRRFS outcomes. Conclusions: Sarcopenic obesity is an independent predictor of poor prognosis in patients with CRC. Thus, interventions aimed at increasing muscle mass and reducing visceral fat could potentially improve the prognosis of these patients.

The therapeutic benefit of recently developed mutant KRAS (KRAS∗) inhibitors remains limited by the rapid onset of resistance. Here, we aim to delineate mechanisms underlying acquired resistance and identify actionable targets for overcoming this clinical challenge. Previously, we identified syndecan-1 (SDC1) as a key effector for pancreatic cancer progression whose surface expression is driven by KRAS∗. By leveraging both pancreatic and colorectal cancer models, we show that surface SDC1 expression initially diminishes upon KRAS∗ inhibition but recovers in tumor cells that bypass KRAS∗ dependency. Mechanistically, we reveal that YAP1 activation drives the recovery of SDC1 surface localization to enhance macropinocytosis-mediated nutrient salvaging and activation of multiple receptor tyrosine kinases for tumor maintenance, promoting resistance to KRAS∗-targeted therapy. Overall, our study provides a strong rationale for targeting the YAP-SDC1 axis to overcome resistance to KRAS∗ inhibition, thereby revealing promising therapeutic opportunities for improving the clinical outcome of patients with KRAS∗-mutated cancers.