| Abstract |
Concomitant with progressive loss of lymphocytoid structure during
repeated mouse passage, a methylcholanthrene-induced lymphoid neoplasm
(P388) acquired increased ability to survive in vitro, where it changed
morphologically to a reticulum cell sarcoma capable of continuous
cultivation. Originating in a DBA/2 mouse as a neoplasm clearly
lymphocytic in structure, P388 was converted to ascitic form in the first
mouse transfer. At the sixth mouse passage, alternate passage of cells
through tissue culture and mouse was started, continuing through 17 cycles.
During these culture attempts, the lymphoid character of the neoplasm was
preserved with only slight variation, as observed both in vivo and in
vitro. Maximum in vitro sunival time in these passages was 17 days. A
second set of culture trials was carried out with cells from the 47th and
later consecutive mouse passages. Here it was found that (1) the structure
of P388 cells in vivo had altered toward a cell type corresponding to an
atypical hemocyto-blast, and (2) the in vitro survival time of these cells
had increased to upwards of 30 days. P388 cells taken from the 49th
consecutive mouse passage were maintained in one culture for 51 days.
During this period, neoplastic cells underwent morphologic alteration to a
larger, more ameboid form containing many cytoplasmic vacuoles. The
ascitic cells emerging from intraperitoneal inoculation of this culture
into mice showed a correspondingly altered structure. They were much
larger and more vacuolated, and many multinucleated forms were present.
Cells isolated directly on glass from the ascites of this animal have been
cultivated continuously for months, through four serial subcultures. In
vitro, the "derived" line (P388D1) shows much pleomorphism with many
spindle, stellate, multilobular, and multi-nucleated forms. These cells
actively phagocytize carbon particles and in general behave as reticulum
cells. Continuous mouse passage of P388 was maintained in (BALB/c X
DBA/2)F1, hybrid mice. P388D1, was found capable of killing DBA/2, (BALB/c X
DBA/2)F1, and (C57BL X DBA/2)F1, mice, but not other strains lacking DBA/2
parentage, such as C57BL and BALB/c. This indicates that P388D1), was
derived from neo-plastic cells of the original line of DBA/2 origin.
8.40x10^5 cells of P388D1, killed (BALB/c X DBA/2)F1, hybrids in 20.6 days
(average), whereas, 1.35x10^5 cells of P388 at the 47th consecutive mouse
passage killed similar hybrids in 11.8 days (average). The in vitro
conversion of P388 into a reticulum cell sarcoma has been repeated twice,
the "derived" lines in the three instances showing characteristics
differing only slightly from one another, and all three being thus far
continuously cultivated.
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