Spectroscopy and Molecular Changes in Cancer Cells - Vibrational Spectroscopy for Tissue Analysis - page 25

Chan et al. [24], in a study based on detecting neoplastic and normal
hematopoietic cells, show that spectral bands are mainly indicative of
nucleotide confirmation (600-800 cm −1 ), backbone geometry and phosphate
ion interactions (800-1200 cm −1 ), electronic structure of the nucleotides
(1200-1600 cm −1 ), and C-C and C-H modes due to proteins and lipids. In
addition, amide vibrations such as the amide I band (due to C=O stretch-
ing [18,19]) and amide III band (due to C-N stretching and C-N bending
[18,19]) in proteins are identifiable. In addition, they could recognise the
peaks that are due to ring breathing modes in DNA bases, such as modes
at 678 cm −1 , 785 cm −1 , 1337 cm −1 , 1485 cm −1 , 1510 cm −1 , and 1575 cm −1 . Because
of the reduction in the height of these peaks, it was concluded that the
overall DNA concentration is significantly lower in transformed cells than
in normal ones.
This was further confirmed by the similarly reduced intensity of the
1093 cm −1 mode of the symmetric PO 2 − vibration of the DNA backbone.
However, it was illustrated that peaks that are mainly due to protein
vibrations are significantly stronger in transformed cells than in normal
cells. A peak located at 1447 cm −1 was used as a marker mode for the protein
concentration, and the 1093 cm −1 phosphate backbone vibration as a marker
mode for DNA concentration. Furthermore, the 813 cm −1 and 1240 cm −1 were
considered as the position of the two most distinct peaks for RNA, indicating
a slightly elevated concentration of RNA in the transformed cells. Other dis-
tinct RNA modes include the ribose vibrations at 867 cm −1 , 915 cm −1 , and
974 c m −1 . It was concluded that transformed cells have lower concentrations
of nucleic acid and higher concentrations of proteins.
Feld et al. [23] studied liposarcomas. Raman spectra were obtained from
liposarcomas and normal tissues. The spectrum of normal tissues shows
lipid bands. In addition to lipid bands, the spectrum of liposarcoma shows
carotenoid bands at 1528 cm −1 and 1156 cm −1 . The intensity ratio of the CH 2
bending mode at 1142 cm −1 to the C=C stretching band at 1667 cm −1 was
observed to decrease with the grade of the malignancy.
It has also been shown [25] that nuclear content is increased in colon can-
cer. This can be concluded from more intense peaks at 1662, 1576, 1458, and
1340 cm −1 , corresponding to nucleic acids in carcinoma samples.
In a study focused on breast pathology [26], Hanlon et al. found three
Raman bands characteristic of fatty acids (1657, 1442, and 1300 cm −1 ). The
most prominent bands in the spectra were related to structural protein
modes (1667, 1452, 1260, 890, and 820 cm −1 ).
Peak intensities related to glycogen and phosphodiester groups of nucleic
acids were found to be different among normal lung cancer samples [27].
Wang et al. showed that bands at 1030 cm −1 and 1050 cm −1 are found fre-
quently in glycogen-rich tissues, and can be assigned as CH 2 OH vibrations
and the C-O stretching coupled with C-O bending of the C-OH carbohy-
drates, respectively. The band at 1080 cm −1 was assigned to symmetry phos-
phate stretching and glycogen, and 1241 cm −1 to the asymmetric phosphate