Ni Ni Moe Myint - Presenter Profile

Blood: An Answer to Fighting Cancer

In this article, Ni Ni Moe Myint describes her research into the use of blood testing as a new way to diagnose cancer.

About My Research

Prevention is the best cure. Finding cancer-causing mutations early will allow chemopreventive measures to be implemented as quickly as possible, leading to increased recovery and survival rates.

Cancer is a global killer, responsible for more than 5 million deaths worldwide annually with cancer-related deaths predicted to rise more than double in the next 20 years. Colorectal cancer (CRC) is one of the five most common cancers worldwide. In the UK alone, CRC contributes to second leading cause of cancer-related deaths with approximately 20,000 deaths recorded annually.

CRC can arise from either hereditary causes or mutations that occur stochastically as we age, which leads to CRC patients showing various clinical features and making it challenging in terms of diagnosis and providing effective treatments. Defects in various cellular pathways can cause CRC but each with distinct disease characteristics; therefore, targeting a specific cancer-causing gene would deliver a better outcome in the shortest time possible. Current 5-year survival rate for patients is estimated at 60% but this is drastically reduced to <10% for those at advanced stages, highlighting the need for efficient, early detection methods to improve mortality and morbidity. At present, colonoscopy is the gold standard diagnostic option for detection of early colorectal polyps. It is a highly sensitive method (>80% detection) but at a cost of undergoing a time-consuming and invasive procedure.

Current early diagnostic methods are limited either in their sensitivity or clinical applicability. Colonoscopy is an invasive procedure which makes it unsuitable for screening large population for the purpose of risk stratification. An alternative diagnostic option of faecal occult blood testing is considered to be an inadequate method for early screening due to its low sensitivity (<40%) in detecting small lesions. In this respect, circulating cell-free DNA (cfDNA) offers an interesting venue as a marker of early cancer status. Cell-free DNA refers to small DNA fragments that are released from dying cells into blood, and the fragments shed from cancer cells would possess cancer-specific mutations.

Using a sensitive molecular technique called polymerase chain reaction (PCR), it is proposed that cancer-specific mutations can be detected in fragmented cell-free DNA extracted from a small volume of blood (1-5ml). Polymerase chain reaction works by targeting and amplifying a DNA sequence of interest whilst blocking the interference of ‘junk’ DNA sequences by using a specific molecular probe. This is essentially looking for a needle in a haystack using a strong, fluorescent magnet. This technique allows the targeted DNA sequence containing the mutation of interest to be detected with high sensitivity and specificity.

My Research Findings

Defects in various molecular pathways can cause cancer. Colorectal cancer is an umbrella term for a group of cancers with distinct molecular pathways and each has particular molecular characteristics. Therefore, in order for this cfDNA-based liquid biopsy approach to be clinically relevant, this technique needs to be validated using frequently implicated genes/mutations in early stages of colorectal cancer. As cancer progresses, its genetic profile changes as it acquires additional mutations. For the purpose of my research, validation of the PCR molecular technique will be tailored for cancer-driver (initiating) mutations primarily found in early stage lesions.

Validation of this molecular technique works by analysing DNA extracted from tumour tissues fixed in paraffin. Using a specific PCR platform called digital droplet PCR, specific mutations can be targeted for detection at sub-nanogram (<10-9) level. Digital droplet PCR works by generating picogram (10-12) volume of tiny droplets coated in specialised oil so that each droplet contains one or two DNA fragments. Subsequently, droplets are used to perform PCR and droplets containing a DNA sequence with mutation would release a fluorescent signal by the virtue of specific molecular probe targeted to a mutated region. This enables screening of samples for most frequent gene mutations in early colorectal polyps.

Following this, tissue samples that are positive for specific mutations will be selected for plasma screening. Each patient has consented for collection of tissue and blood (plasma) samples. By analysing respective plasma samples, genetic/mutation profiles obtained from tissue and plasma can be compared and matched. High degree of match between the tissue and plasma profiles obtained from the same patient would support the applicability of cfDNA-based early detection method as a surrogate for colonoscopic biopsy.

This research project aims to validate and establish cfDNA-based mutation detection as a non-invasive, liquid biopsy where a panoramic mutation profile output can be obtained with a quick turnover. Challenges for this project stemmed from the biology of cfDNA: these cell-free DNA fragments are released into the circulation as a collateral event to cell death processes either due to physiological causes or a diseased state. Consequently, presence of cfDNA is scarce in the blood, making it very challenging to detect cancer-specific mutations. However, digital droplet PCR is a very sensitive molecular platform capable of detecting targeted sequences that exists in a background of 1000-fold junk ‘wild-type’ DNA (i.e. DNA without mutation). This level of sensitivity and specificity has been successfully demonstrated for two frequently mutated genes (BRAF and KRAS) implicated in early stages of colorectal cancer. This project is currently in the process of tailoring this molecular technique to encompass other genes known for initiation of colorectal lesions. This approach, once validated for sensitivity and specificity, can potentially be used to screen the population for presence of mutations implicated in early stages of colorectal cancer. Especially for asymptomatic individuals in early stages, this enables them to receive appropriate preventive treatments to stop cancer before it progresses further.

About Ni Ni Moe Myint

Ni Ni Moe Myint is a PhD Student at the University of Leicester (2015)Ni Ni Moe Myint is a research student working towards completion of her doctoral degree in the Department of Cancer Studies. Ni Ni is supervised by Professor Karen Brown and Dr Alessandro Rufini.

Ni Ni will present her work at the Festival of Postgraduate Research 6 July 2015 - see Ni Ni's Festival poster.

The Festival is open to all members of the University community and the public - book your place here.

Contact Ni Ni

Department of Cancer Studies

University of Leicester

University Road

LEICESTER

LE1 7RH

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