Prevention and therapy of colorectal cancer

The Safe Soluble Compound Dehydroascorbic Acid Inhibits Various Upstream and Downstream Effectors of PI3K and KRAS Signaling Pathways in Undruggable PIK3CA/KRAS-Mutant Colorectal Cancer Stem-Like Cells

Efforts to develop effective drugs targeting PI3K and KRAS signaling pathways in PIK3CA/KRAS-mutant colorectal cancer stem cells (CRCSCs) remain challenging. Finding safe compounds that can easily enter CRCSCs with the ability to target metastasis-driver gene CXCR4 and pluripotency network genes as key upstream and downstream effectors of both PI3K and KRAS signaling pathways may provide promising results. PIK3CA/KRAS-mutant CRCSCs display high expression of glucose transporters (GLUTs) on their cell membrane and a glycolytic phenotype providing an opportunity to deliver antiglycolytic compounds into these cells via the GLUTs. CRC patients with low levels of vitamin C in their plasma show a shorter survival suggesting the ability of this vitamin at the physiologic levels for caspase-3 activation and apoptosis in CRCSCs. Vitamin C in an oxidized form (L-dehydroascorbic acid; L-DHA) with antiglycolytic activity can be taken up into CRC cells via the GLUTs. This may provide selective toxicity on CRCSCs and affect CXCR4 and stemness markers genes expression in these cells. To this end, we treated PIK3CA/KRAS-mutant LS174T cells with high glycolytic activity as an attractive model for CRCSCs with L-DHA equal to the pharmacological levels of vitamin C in human plasma, after which cell numbers, metabolic activity, proliferation-rate, CXCR4 and pluripotency network genes expression, caspase-3 activity with apoptosis were evaluated. 48 h post-treatment with 100- to 1000 µM L-DHA, cell numbers were decreased and measured to be 70-47% control. L-DHA with selective toxicity on LS174T cells diminished metabolic activity and cell proliferation-rate to 1.4-0.8 (Control OD = 1.5) and 92-54.5% respectively with no toxicity on PBMCs. L-DHA decreased CXCR4, Bmi-1, Sox-2 and Oct-4 expression to 45%, 85%, 45% and 48% control respectively followed by caspase-3 reactivation by 2.5 to 4.9-fold increases and induction of apoptosis ranging from 0.5% to 58.3% for 100- to 1000 µM L-DHA. According to our data, CRC stem-like cells were highly sensitive to L-DHA in in-vitro. L-DHA selectively targeted LS174T cells and successfully reactivated caspase-3 and apoptosis in these cells. CXCR4, stemness marker genes and metabolic activity appear to be promising targets of L-DHA. Our results may provide a new therapeutic approach to target selectively GLUT-overexpressing PIK3CA/KRAS-mutant CRCSCs using L-DHA with no toxicity on normal cells.

Clinical characteristics and treatment outcomes of colorectal cancer in renal transplant recipients in Korea

PURPOSE

Transplant recipients in Asia appear to be at a higher risk for developing colorectal cancer (CRC). This study was performed to identify the clinicopathological features and oncologic outcomes of CRC in post-renal transplants in Korea.

MATERIALS AND METHODS

We retrospectively reviewed the records of 17 patients with CRC out of 2,630 recipients who underwent renal transplantation between 1994 and 2007. These patients (transplant group) were compared with general CRC patients (n=170, control group) matched, based on the closest date of surgery to the transplant group.

RESULTS

During 29.7 months of the median follow- up period, the recurrent and survival rates from recurrence were worse in the transplant group than in the control group (35.2% versus 15.2%; p=0.048 and p=0.025). The 2-year patient survival rate of the transplant group was significantly worse than the control group in advanced cancer (stages III-IV; 45.7% versus 71.6%; p=0.023). In early cancer (stages 0-I), there was no significant difference in 5-year patient survival rate between the two groups (100% versus 92.6%, respectively; p=0.406).

CONCLUSION

In spite of a poor prognosis of advanced CRC in the transplant group, the early stage CRC of the transplant group showed a comparable oncologic outcome compared with the control group. Regular screening and early detection of CRC are essential in the post-transplant setting.

Colon and rectal cancer after renal transplantation

Increased cancer risk after renal transplantation is believed to be a consequence of continuous immunosuppression. However, the risk of colorectal cancer (CRC) after renal transplantation is controversial and has received limited study. Accumulating evidence suggests that colon and rectal cancers have different characteristics in the post-renal transplant patient (PRTP) and should be evaluated separately in transplant registries. This article reviews the current literature evaluating CRC diagnosed in PRTPs, focusing on clinical characteristics and treatment outcomes.

Pathophysiology, clinical presentation, and management of colon cancer

Colon cancer is believed to arise from two types of precursor polyps via two distinct pathways: conventional adenomas by the conventional adenoma-to-carcinoma sequence and serrated adenomas according to the serrated adenoma-to-carcinoma theory. Conventional adenomas arise from mutation of the APC gene; progression to colon cancer is a multistep process. The fundamental genetic defect in serrated adenomas is unknown. Environmental factors can increase the risk for colon cancer. Advanced colon cancer often presents with symptoms, but early colon cancer and premalignant adenomatous polyps commonly are asymptomatic, rendering them difficult to detect and providing the rationale for mass screening of adults over age 50.