Page 64 - Read Online

available cell lines represent different bladder cancer
subtypes and varying degrees of genetic complexity
depending on the sample of origin. However, continuous
passages and culture of cells in vitro selects the cells better
adapted to in vitro culture, reducing the heterogeneity,
and promoting the acquisition of new mutations. Several
human bladder cancer cell lines have been established
and used over the years for multiple purposes. As a result
of these studies, genomic and pharmacological profiles
of 28 human bladder cancer cell lines are now available
in the Cancer Cell Line Encyclopedia (https://www.
broadinstitute.org/software/cprg/?q=node/11). [30]

Our in vitro studies on UBC were based on three different
human cancer cell lines: 5637, T24 and HT1376. These
cell lines have been widely used to evaluate efficacy of
anticancer drugs. Although significant heterogeneity and
Figure 2: Schematic representation of the study design to complexity were detected between them, their genomic
establish a patient-derived tumor xenograft model. The original profiles exhibited a similar pattern to human UBC. [31]
tumor and tumors grown in mice can be analyzed and compared The NMIBC cell line 5637 and the two MIBC cell lines
using fresh or Formalin-fixed, paraffin-embedded tumor samples T24 and HT1376 cover the most frequent subtypes of
for histology and immunoexpression of specific markers. FFPE: UBC; T24 represents an FGFR3/Cyclin D1 subtype,
Formalin-fixed, paraffin-embedded
while 5637 and HT1376 represent the E2F3/RB1
Subrenal capsule xenografting of primary bladder tumor pathway mutational profile, with the former representing
in mice has been recently described with higher tumor a less aggressive phenotype and the later bearing more
take rates and retention of the genetic and morphological invasive and metastatic properties. [31] Figure 3 shows
characteristics of the primary tumor. Both subcutaneous the karyogram of HT1376 cell line that presented a
[24]
and subcapsular renal sites are not the orthotopic location near-tetraploid karyotype with complex arrangements in
for bladder cancer growth; however, the latter seems to be a several chromosomes.
more favorable environment for PDX survival and growth
as is also observed for other cancer. [25,26] The use of PDXs We have used the cell lines 5637, T24, and HT1376
mice is feasible and allows a higher predictive power than to evaluate the effect of everolimus and temsirolimus
other animal models. [27,28] Because of this, PDX will be an [sirolimus analogs and mammalian target of rapamycin
increasingly valuable tool in the evaluation of human tumor (mTOR) inhibitors] in UBC cells. mTOR signaling was
response to traditional and new chemotherapeutic drugs. found to play an important role in cell growth, survival,
proliferation, and angiogenesis in eukaryotic cells and its
UBC CELL LINES dysregulation was detected in many cancer, including in
UBC, where it is believed to have potential for prognostic
Cell lines established from tumors and adapted to information and targeted therapy. [32-34] Therapies targeting
proliferate in culture have been extensively used in mTOR are already used in the clinics to treat renal cell
cancer research and their use has significantly improved carcinoma and mantle cell lymphoma. [35] Their potential
our knowledge of cancer biology. Cancer cell lines have application to the treatment of other cancer is studied,
an important role in the study of the biological effects particularly in combinational strategies, to overcome
of genetic alterations in different tumor subtypes, in the resistance and enhance efficacy of standard therapies.
identification and characterization of genes involved According to our studies, sirolimus analogs exert a slight
in cancer initiation and progression, and drug testing. interference on proliferation, apoptosis, and autophagy
In vitro assays using panels of cell lines are used as in these cancer cell lines. The NMIBC cell line 5637 was
first line models in the preclinical development of new the most sensitive to mTOR inhibitor treatment alone. [36,37]
drugs to discover, validate, and evaluate the potential Considering other preclinical studies where sensitivity to
of new therapeutic agents. [29] Gene expression can be mTOR inhibitors has been associated with PTEN loss, [38]
manipulated in cell culture to introduce gain- or loss- we expected that the UBC cell lines 5637 and HT1376
of-function mutations to evaluate the biological effect (both of which harbor deletion of PTEN), would respond
on cell survival and proliferation, both in vitro and in well to sirolimus analogs. However, only 5637 was
vivo through the use of xenografts or syngeneic models. sensitive to monotherapy. More recently, in patients with
For more than a half-century, tumor cell lines served as MIBC treated with everolimus, PTEN loss was associated
a foundation for cancer research since they are easy to with resistance to treatment with the unhampered
use and cost-effective. Within the bladder cancer field, feedback loop driving PI3K/Akt activation suggesting

54
Journal of Cancer Metastasis and Treatment ¦ Volume 2 ¦ Issue 2 ¦ February 29, 2016 ¦