Missense mutations in MLH1, MSH2, KRAS, and APC genes in colorectal cancer patients in Malaysia

KRAS Mutational Profiles among Colorectal Cancer Patients in the East Coast of Peninsular Malaysia

BACKGROUND

KRAS is a key driver gene in colorectal carcinogenesis. Despite this, there are still limited data on the mutational status of KRAS amongst colorectal cancer (CRC) patients in Malaysia. In the present study, we aimed to analyze the KRAS mutational profiles on codons 12 and 13 amongst CRC patients in Hospital Universiti Sains Malaysia, Kelantan, located on the East Coast of Peninsular Malaysia.

METHODS

DNA were extracted from formalin-fixed, paraffin-embedded tissues obtained from 33 CRC patients diagnosed between 2018 and 2019. Amplifications of codons 12 and 13 of KRAS were conducted using conventional polymerase chain reaction (PCR) followed by Sanger sequencing.

RESULTS

Mutations were identified in 36.4% (12/33) of patients, with G12D (50%) being the most frequent single-point mutation observed, followed by G12V (25%), G13D (16.7%), and G12S (8.3%). No correlation was found between mutant KRAS and location of the tumor, staging, and initial carcinoembryonic antigen (CEA) level.

CONCLUSION

Current analyses revealed that a significant proportion of CRC patients in the East Coast of Peninsular Malaysia have KRAS mutations, where this frequency is higher compared to those in the West Coast. The findings of this study would serve as a precursor for further research that explores KRAS mutational status and the profiling of other candidate genes among Malaysian CRC patients.

Gene Therapy Targeting p53 and KRAS for Colorectal Cancer Treatment: A Myth or the Way Forward?

Colorectal cancer (CRC) is the third most commonly diagnosed malignancy worldwide and is responsible as one of the main causes of mortality in both men and women. Despite massive efforts to raise public awareness on early screening and significant advancements in the treatment for CRC, the majority of cases are still being diagnosed at the advanced stage. This contributes to low survivability due to this cancer. CRC patients present various genetic changes and epigenetic modifications. The most common genetic alterations associated with CRC are p53 and KRAS mutations. Gene therapy targeting defect genes such as TP53 (tumor suppressor gene encodes for p53) and KRAS (oncogene) in CRC potentially serves as an alternative treatment avenue for the disease in addition to the standard therapy. For the last decade, significant developments have been seen in gene therapy for translational purposes in treating various cancers. This includes the development of vectors as delivery vehicles. Despite the optimism revolving around targeted gene therapy for cancer treatment, it also has various limitations, such as a lack of availability of related technology, high cost of the involved procedures, and ethical issues. This article will provide a review on the potentials and challenges of gene therapy targeting p53 and KRAS for the treatment of CRC.

CircBACH1/let-7a-5p axis enhances the proliferation and metastasis of colorectal cancer by upregulating CREB5 expression

Background

In this study, we investigated the influences of circBACH1 on the proliferation, metastasis, migration, and apoptosis of human colorectal cancer LoVo cells and explored the molecular mechanism of its effect to guide the clinical diagnosis, treatment, and follow-up of colorectal cancer.

Methods

The expression of circBACH1 in colorectal cancer cells was measured to determine the high expression of BACH1 in colorectal cancer (CRC). LoVo was selected for a follow-up experiment. Then, quantificational reverse transcription-polymerase chain reaction (qRT-PCR) and biotinylated let-7a-5p probes were used to confirm that the expression of let-7a-5p was lowered in colorectal cancer, and let-7a-5p was the downstream target of BACH1 in CRC. Cell counting Kit-8 (CCK-8), Transwell, and wound repair experiments confirmed that BACH1 augmented the proliferation, migration, and metastasis of CRC by regulating let-7a-5p. The apoptosis rate was measured by flow cytometry. It was concluded that BACH1 inhibited apoptosis by regulating let-7a-5p in CRC. The results of the bioinformatics analysis showed that CREB5 was overexpressed in CRC by qRT-PCR and Western blot. The results of qRT-PCR, CCK-8 assay, Transwell assay, and flow cytometry showed that let-7a-5p inhibited the proliferation, migration, and invasion of CRC cells through targeting CREB5 and augmented cell apoptosis. According to tumor growth and the determination of CREB5 by Western blot, BACH1 can affect the proliferation of CRC cells through CREB5.

Results

Overall, our study confirmed that BACH1 and CREB5 increased, while the expression of let-7a-5p was lowered in colorectal cancer cells. These different expressions enhance the proliferation, metastasis, and migration of colorectal cancer cells and inhibit colorectal cancer cells' apoptosis.

Conclusions

Our study clearly illustrates the molecular mechanism of circBACH1 acting on colorectal cancer, which can be used as a therapeutic target to augment colorectal cancer treatment.

Molecular Targeted Drugs and Treatment of Colorectal Cancer: Recent Progress and Future Perspectives

Nowadays, colorectal cancer is the fourth most common type of tumor all over the world. When diagnosed, ∼50%-60% of tumors have metastasized, thus resulting in a grim prognosis. Chemotherapy is regarded as standard treatment for patients with colorectal cancer, however, limitations of chemotherapy cannot be ignored, such as low selectivity, insufficient concentrations in tumor tissues, and systemic toxicity. Recently, six targeted drugs have been approved by the U.S. Food and Drug Administration (FDA) for treatment of metastatic colorectal cancer (mCRC), including bevacizumab, aflibercept, regorafenib, cetuximab, and panitumumab. The development of these drugs marked significant advancement in the field of mCRC therapy. The addition of biologic agents to chemotherapy has prolonged the median overall survival. Now, many investigational drugs are under clinical trials, of which programmed death (PD)-1/L1 has drawn much attention. In this review, new biologic agents under clinical trials such as MEK/MET/RAS/RAF/PD-1 inhibitors with potentials for mCRC treatment are concluded by describing targeted drugs approved by FDA, to offer new insights into global trends and future development.

Analysis of Hereditary Nonpolyposis Colorectal Cancer in Malay Cohorts using Immunohistochemical Screening

BACKGROUND

Lynch syndrome (LS) is an inherited predisposition to colorectal, endometrial (uterine) and other cancers. Although most cancers are not inherited, about 5 percent (%) of people who have colorectal or endometrial cancer have the Lynch syndrome. It involves the alteration of mismatch repair (MMR) genes; MLH1, MSH2, MSH6 or PMS2. In this study, we analyzed the expression of MMR proteins in colorectal cancer in a Malay cohort by immunohistochemistry.

MATERIALS AND METHODS

A total of 17 patients were selected fulfilling one of the Bethesda criteria: colorectal cancer diagnosed in a patient aged less than 50 years old, having synchronous and metachronous colorectal cancer or with a strong family history. Immunohistochemical staining was performed on paraffin embedded tumour tissue samples using four antibodies: MLH1, MSH2, MSH6 and PMS2.

RESULTS

Twelve out of 17 patients (70.6%) were noted to have a family history. A total of 41% (n=7) of the patients had abnormal immunohistochemical staining with one or more of the four antibodies. Loss of expression were noted in 13 tumour tissues with a negative staining score <4. Of 13 tumour tissues, four showed loss expression of MLH1. For PMS2, loss of expression were noted in five cases. Both MSH2 and MSH6 showed loss of expression in two tumour tissues respectively.

CONCLUSIONS

Revised Bethesda criteria and immunohistochemical analysis constituted a convenient approach and is recommended to be a first-line screening for Lynch syndrome in Malay cohorts.

Comparison of K-ras mutations in lung, colorectal and gastric cancer

K-ras is involved in the EGFR pathway that regulates cell survival, motility and proliferation, as well as angiogenesis and metastasis. It is also essential for carcinogenesis. The K-ras mutation status can be used to predict the therapeutic efficacy of targeted drugs such as cetuximab. The aim of this study was to compare K-ras mutation in different types of cancer. Nested and COLD-PCR were used to detect K-ras mutations. The Chi-squared test was used for statistical analysis. In this study, the total K-ras mutation frequency was found to be 9.09, 18.61 and 6.67% in lung, colorectal and gastric cancer, respectively. Similar K-ras mutation frequencies were detected among sample types and genders for lung and gastric cancer, with the exception of colorectal cancer. However, age had no impact on the K-ras mutation rates.