Med Hypotheses. 1984 Feb;13(2):125-36. |
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Neoplasia--a stem cell pathology.
Zajicek G.
Cell proliferation in the organism is accompanied by cell displacement.
Proliferating tissues exhibit three key characteristics: a site of origin of
the stem cell, a tissue radius along which all constituents except the stem
cell are displaced and a periphery where cells are eliminated. The tissue thus
consists of two cell types: Stem and transitional. Since only the first resides
permanently in the tissue any lasting change observed in the tissue is directed
by the stem cell. Each stem cell division results in two cell types: one
replacing the parent cell to remain a stem cell, while the other originates an
outward displaced transitional cell clone whose life span is limited. In the
normal state, the stem cell pool is constant, although its replenishment
capacity is limited. Neoplasia is regarded here as a purposeful tissue
alteration originating in a stem cell change manifested by: Aneuploidy,
maturation arrest, stem cell pool enlargement and increasing cell turnover.
Stem cells are assumed to secrete a substance 'A' necessary for a proper tissue
function, whose production is impeded by carcinogens, mainly by stem cell
depletion. Since however stem cell replenishment is limited, the organism grows
a specialized organ, the neoplasm, producing a less efficient substitute for
'A', denominated here as substance 'B'. Neoplastic growth is indirectly
dependent upon the abundance of substance 'A', the supply of which should be
followed by a reduction of neoplastic mass. Neoplasia is thus viewed here as a
protective function directed by the stem cell and linked with
"oncogenes". Each determined stem cell is harbouring a specific oncogene
and exhibits a typical neoplasm. Since the theory predicts that neoplastic
growth indirectly depends upon the abundance of substance 'A', it may be tested
by investigating the effect of substance 'A' producing stem cells upon the
growing neoplasm. Their supply to the organism should be followed by a
reduction of the neoplastic mass.
PMID: 6717314 [PubMed - indexed for MEDLINE]