Cancer Detection with a Drop of Blood

Detectia cancerului intr-o faza incipienta este critica pentru sansa de supravietuire a pacientului. Un alt factor important este si detectia non-invaziva care ar scuti pacientul de neplacerile unei biopsii (metoda invaziva).

Descoperirile din ultimii ani in cercetarea moleculara fac posibila detectia non-invaziva a cancerului folosind monstre de fluide cum ar fi sangele sau saliva.

Una dintre descoperiri se refera la mobilitatea secventelor de  ADN din corpul uman. In general, ADN-ul se gaseste in nucleele celulelor vii. Cand celulele mor, fragmente din acesta se pot desprinde si circula libere in sange (aceste fragmente sunt numite si cell-free DNA).

Pe baza acestor descoperiri, o echipa de  cercetatori de la Universitatile California din Los Angeles si California de Sud a creat un program software care detecteaza cancerul analizand secventele de ADN folosind doar o picatura de sange.

Mai mult, programul (denumit CancerLocator) detecteaza si tesutul unde cancerul este localizat. 


Detectia cancerului se face prin analiza modificarilor chimice ce apar in secventa de ADN.

Va voi explica putina genetica (si sper sa nu va plictisesc) pentru a intelege cum functioneaza acest program de detectie.
Toate celulele din organismul uman contin aceeasi secventa de ADN. Diferitele tipuri de celule (de plaman, ficat, rinichi, etc) sunt obtinute prin expresia diferitelor gene. Metilarea ADN-ului are loc atunci cand un grup de metil se asociaza secventei de ADN si produce activarea sau dezactivarea anumitor gene. Fiecare tip de celula se caracterizeaza printr-un tipar unic de metilare. In cazul celulelor canceroase, acest tipar este modificat.  Aceste modificari sunt folosite de CancerLocator pentru a detecta si localiza tumora.

 

Programul foloseste Machine Learning pentru a invata sa recunoasca intre tiparele normale si cele canceroase, fiind antrenat pe baza de date dipsonibile in Atlasul Genomului Cancerului.

S-au realizat teste de sange pe 29 de pacienti cu cancer la ficat, 12 cu cancer la plamani si 5 paciente cu cancer de san, eroarea de diagnosticare a cancerului fiind redusa de la 60 de procente la 26,5!!!

CancerLocator detecteaza cancerul inclusiv din secvente foarte mici de ADN (care sunt specifice cancerului in faze incipiente).

Asadar, CancerDetector este o metoda non-invaziva de detectie a cancerului in faze incipiente, putand fi folosita si pentru a monitoriza rezultatele unui tratament, pentru a semnala reaparitia cancerului sau permite studii care conduc la tratamente personalizate. 

Este prima metoda care detecteaza cancerul pe baza analizei tiparului de metilare ADN aprobata FDA. 
Sursa... 

EN:
Early-stage cancer detection is critical for the survival rate of patient. Another important factor is the invasiveness of detection (for example, a biopsy is can detect almost anything, but is an extremely unpleasant experience for the patient).

Recent developments in molecular research make non-invasive cancer detection using fluid samples, such as blood or saliva, possible.

One of the recent discoveries made, concern the mobility of fragments of DNA sequences in the human body. In general, DNA is usually located in the nucleus of living cells. However, when the cell dies, fragments of this DNA may exit the nucleus and move freely through the blood stream (these fragments are called cell-free DNA).

Based on these discoveries, a research team from the University California Los Angeles and the University Southern California developed a software program to detect cancer based on analysis of DNA sequences from a drop of blood. 
 

Additionally, this program (called CancerLocator) is able to detect the tissue from which a particular DNA sequence come from.

We will now go into a little bit of theory (please bear with me), in order to understand how this new detection program works.

Cancer detection is based on chemical changes in the DNA sequences. 

The cells of the human body contain the same DNA sequence. Different cell types (e.g. liver cells, lung cells, skin cells) are obtained by different “genes expressions” (the way genes manifest themselves in such a way that a certain fenotype is realized). DNA Methylation happens when a “methyl group” (a chemical substance) is “tagged” (added) to the DNA sequence and turns some cells on or off. Each type of cell is characterized by a unique pattern of DNA methylation. Certain patterns are linked to certain parts of the human body, thereby allowing analysis to match certain cells to certain body parts. This pattern is altered slightly in the cancerous cells, thereby also allowing analysis of this pattern to reveal the presence of cancer. 

CancerLocator analyses these alterations in the DNA methylation patterns in order to detect and localize the tumor. 

The software uses Machine Learning to differentiate between cancerous and normal cells, being trained on a database available on Atlas of Cancer Genome.

Tests were performed on 29 patients with liver cancer, 12 patients with lung cancer and 5 patients with breast cancer. The diagnosis error was reduced from 60% to 26,5% using CancerLocator.

CancerLocator is able to detect cancer from very small DNA sequences which are specific to cancer, and in its very early stages.

Therefore, CancerDetector is a very interesting and promising cancer detection and localization tool. It can also be used to monitor the results of a medication treatment; to check whether the cancer may be re-generating during or after the treatment, and to conduct studies in order to improve the personalized medicine. 


This is the first method of its kind approved by the U.S. Food and Drug Administration.

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