e-ISSN: 2582-5208 International Research Journal of Modernization in Engineering Technology and Science Volume:02/Issue:09/September-2020
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AN INTRODUCTION TO “SEED” AND “SOIL” HYPOTHESIS OF METASTASIS Susamman Biswas*1 *1B.Sc
(Zoology), School of Sciences(SOS), Indira Gandhi National Open University(IGNOU), Kolkata, West Bengal, India.
ABSTRACT This is a brief introduction of Seed and Soil hypothesis of Cancer Metastasis. Here I have tried to summarize the main points of Seed and Soil factors. This mechanism is mainly seen in cancer progression and colonization in an organ. But one thing need to be understood, Seed and Soil is a hypothesis as it is not found in all cases. Keywords: Cancer, Metastasis, Cytokine, EMT, MET.
I.
INTRODUCTION
Cancer has a dangerously unique feature, it spreads. That spreading is called as metastasis. Metastasis includes many features and components. Dr. Stephen Paget divided them into two categories and proposed a hypothesis. They are called as “Seed”s and “Soil”s and the hypothesis is commonly called as Seed and Soil Hypothesis [1]. This is published in 1889 and still considered as the most deserved to be true.
II.
INITIATION OF METASTASIS
Initiation of metastasis is the initiation of cancer spreading. Cells of one specific source, like malignant tumor are found in distal locations. It means cells are spreading. They travel through blood and are known as Circulating Tumor Cells(CTC). After settling down the are known as Disseminating Cancer Cells(DTC). But their source must be a malignant tumor [2]. In this spreading Seed and Soil are the most important elements.
III.
SEED IN METASTASIS
Seed is the term used to denote the sources of metastasis. Some important seed factors are as follows EMT-MET: EMT or Epithelial Mesenchymal Transition is a very hallmark feature of metastasis. To transform an epithelial cell into a mesenchymal cell many pathways, molecular factors are responsible which also promote migratory and invasive property[3][4][5][6][7][8][9][10][11][12][13]. EMT-TF or EMT Transcription Factors exhibit pleurotropic effect, which may be responsible to produce EMTs. 3 types of EMTs are found where type 1 and 2 are necessary and found during implantation, embryogenesis, organ development, tissue regeneration but type 3 is found during cancer metastasis[14][15]. MET or Mesenchymal Epithelial Transition cells are the reverse of EMT. MET is needed to colonize and EMT is present in CTC[16][17]. Cancer Stem Cell(CSC): Cancer stem cell aka Tumorigenic Cell aka Tumor Initiating Cell are the type of cell which have stem cell like properties and give birth to a tumor. It is capable of colonization[18][19][20]. Autophagy: It is not clear that how autophagy promotes metastasis, because in some cases autophagy acts pro-metastatic, e.g. caffeine induced autophagy destroys cancer cells[21][22]. Dormant Cancer Cells: Dormant cancer cells are also caller Seed factor because they can remain inactive for years. In dormant state these cells become refractory and maintain quiescence. Many genes like VCAM-1 helps them to reactivate and start metastasis[23][24]. Tumor Secreted Factors: Tumor secreted factors include extracellular vesicles, cytokines, chemokines majorly.
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