90
severe-combined immunodeficient (SCID) or non-obese diabetic-SCID mice with a
defect in the IL2 receptor gamma chain (NOD/SCID/IL2Rγnull-Hu). Yaccoby et al.
(1998) has described SCID-hu model in detail [ 1 ]. Since SCID mice they are devoid
of inherent immune cells, these allow the engraftment of human fetal bone and
human myeloma. Primary myeloma cells do not survive once removed from the
patient but grow in the human bone fragment in SCID-hu, remain restricted to the
human bone microenvironment and manifest typical myeloma disease symptoms.
Newly formed blood vessels at the myeloma tumor site also originate from human
cells and create human bone microenvironment.
NOD/SCID/IL2Rγnull mice have distinct advantage for the study of cellular and
immunotherapy and ensure that adoptively transferred cells are not rejected [ 16 ].
After the inoculation of myeloma cells, tumor growth can be monitored by a rise in
the host’s serum level of human immunoglobulins (hIg) of the M protein isotype by
ELISA, changes in bone calcification by conventional radiography, and by biolumi-
nescence imaging if luciferase transfected myeloma cells have been used.
6.2.2 Radiography and ELISA
Conventional radiography is a low-cost and fast imaging option but has several limi-
tations such as low sensitivity to early osteolytic lesions, as lytic lesions are appar-
ent only after 30–50% of bone mineral density is lost (Fig. 6.1). In addition, diffuse
bone marrow involvement that may not be associated with significant decrease in
density or bone destruction, is not readily detected.
Durie and salmon in 1975 introduced a staging system in myeloma patients,
based upon M-protein level in serum and urine, which correlates well with myeloma
cell mass. This staging system serves as a gold standard in clinical practice [ 17 ].
Studies have shown that circulating hIg levels represent the tumor burden in myelo-
matous mice (Fig. 6.2) and are routinely performed for the evaluation of growth in
tumor burden, pre and post-therapy [ 1 , 18 ]. The levels of human IgG, IgA, κ, and λ
light chains are determined by ELISA. However, there are certain disadvantages in
this approach as the kinetics of the increased hIg levels varies among patients’-
derived myeloma cells and there is a lack in correlation between the time of detec-
tion of hIg and the number of myeloma cells inoculated, marrow plasmacytosis or
other patient characteristic [ 1 ]. This implies that any real time monitoring of
myeloma based on M-protein levels is only good for a particular patient or class of
myeloma cells and cannot be generalized across the board. It also implies that if the
clonal population is altered during the course of the disease then the results may not
be valid. Further, M-proteins alone cannot predict survival or treatment response
accurately, since large quantities of M-protein can be produced by small number of
myeloma cells and vice versa. In addition, this approach may not be useful if the
cells used for inoculation are from non-secretory myeloma patient that constitute
approximately 3% of all myeloma patients.
T.K. Garg and T. Pandey