Claudin-4-adhesion signaling drives breast cancer metabolism and progression via liver X receptor ß.

BACKGROUND: Cell adhesion is indispensable for appropriate tissue architecture and function in multicellular organisms. Besides maintaining tissue integrity, cell adhesion molecules, including tight-junction proteins claudins (CLDNs), exhibit the signaling abilities to control a variety of physiological and pathological processes. However, it is still fragmentary how cell adhesion signaling accesses the nucleus and regulates gene expression. METHODS: By generating a number of knockout and rescued human breast cell lines and comparing their phenotypes, we determined whether and how CLDN4 affected breast cancer progression in vitro and in vivo. We also identified by RNA sequencing downstream genes whose expression was altered by CLDN4-adhesion signaling. Additionally, we analyzed by RT-qPCR the CLDN4-regulating genes by using a series of knockout and add-back cell lines. Moreover, by immunohistochemistry and semi-quantification, we verified the clinicopathological significance of CLDN4 and the nuclear receptor LXRß (liver X receptor ß) expression in breast cancer tissues from 187 patients. RESULTS: We uncovered that the CLDN4-adhesion signaling accelerated breast cancer metabolism and progression via LXRß. The second extracellular domain and the carboxy-terminal Y197 of CLDN4 were required to activate Src-family kinases (SFKs) and the downstream AKT in breast cancer cells to promote their proliferation. Knockout and rescue experiments revealed that the CLDN4 signaling targets the AKT phosphorylation site S432 in LXRß, leading to enhanced cell proliferation, migration, and tumor growth, as well as cholesterol homeostasis and fatty acid metabolism, in breast cancer cells. In addition, RT-qPCR analysis showed the CLDN4-regulated genes are classified into at least six groups according to distinct LXRß- and LXRßS432-dependence. Furthermore, among triple-negative breast cancer subjects, the "CLDN4-high/LXRß-high" and "CLDN4-low and/or LXRß-low" groups appeared to exhibit poor outcomes and relatively favorable prognoses, respectively. CONCLUSIONS: The identification of this machinery highlights a link between cell adhesion and transcription factor signalings to promote metabolic and progressive processes of malignant tumors and possibly to coordinate diverse physiological and pathological events.

The relationship between BRCA-associated breast cancer and age factors: an analysis of the Japanese HBOC consortium database.

BRCA1/2 pathogenic variant prevalence in Japanese breast cancer is unclear. Here, we analyzed BRCA1/2 pathogenic variant prevalence with a particular focus on age factors, using the Japanese HBOC consortium database. All registered subjects were Japanese individuals who underwent BRCA1/2 genetic testing from January 1996 to July 2017 according to the Japanese HBOC consortium database. Cases were extracted and analyzed for each evaluation item. Overall BRCA1 and BRCA2 pathogenic variant prevalence was 11.2% and 9.0% in the cohort of 2366 proband patients, respectively. The age at onset of breast cancer for patients with BRCA1/2 pathogenic variants was significantly lower than that for patients without a BRCA1/2 pathogenic variant. In both BRCA1/2 patients, ages at onset were not statistically significantly different between two subtype groups (ER-positive vs. TNBC). We analyzed the BRCA1/2 pathogenic variant prevalence among age groups in patients with no family history of breast or ovarian cancer. In the TNBC group, the rate of genetic variants was more frequent among younger patients. Our results demonstrated that early breast cancer onset is associated with a BRCA1/2 pathogenic variant in the Japanese population. Younger TNBC patients were more likely to have a BRCA1/2 pathogenic variant irrespective of a family history of breast or ovarian cancer.

Regulation of hypoxia-inducible factor functions in the nucleus by sphingosine-1-phosphate.

Sphingosine kinase 2 (SphK2) is known to phosphorylate the nuclear sphingolipid metabolite to generate sphingosine-1-phosphate (S1P). Nuclear S1P is involved in epigenetic regulation of gene expression; however, the underlying mechanisms are not well understood. In this work, we have identified the role of nuclear S1P and SphK2 in regulating hypoxia-responsive master transcription factors hypoxia-inducible factor (HIF)-1α/2α, and their functions in breast cancer, with a focus on triple-negative breast cancer (TNBC). We have shown SphK2 is associated with HIF-1α in protein complexes, and is enriched at the promoters of HIF target genes, including vascular endothelial growth factor (VEGF), where it enhances local histone H3 acetylation and transcription. S1P specifically binds to the PAS domains of HIF-1α. SphK2, and HIF-1α expression levels are elevated in metastatic estrogen receptor-positive (ER+) and TNBC clinical tissue specimens compared to healthy breast tissue samples. To determine if S1P formation in the nucleus by SphK2 is a key regulator of HIF functions, we found using a preclinical TNBC xenograft mouse model, and an existing selective SphK2 inhibitor K-145, that nuclear S1P, histone acetylation, HIF-1α expression, and TNBC tumor growth were all reduced in vivo. Our results suggest that S1P and SphK2 in the nucleus are linked to the regulation of HIF-1α/2α functions associated with breast cancer progression, and may provide potential therapeutic targets.

Orthotopic Implantation Achieves Better Engraftment and Faster Growth Than Subcutaneous Implantation in Breast Cancer Patient-Derived Xenografts.

Patient-Derived Xenograft (PDX) is now accepted as a murine model that better mimics human cancer when compared to a conventional cancer cell-line inoculation model. Some claim the advantage of orthotopic site implantation of patient tumor (OS) over ectopic implantation into the subcutaneous space (SQ); however, there has been no study that describes a head-to-head comparison of oncological differences between these two models to date. We hypothesize that OS tumors re-transplant and grow better than SQ tumors and are therefore a better model to evaluate tumor aggressiveness. Breast cancer PDXs were generated using the tumors derived from 11 patients into NOD scid gamma (NSG) mice. We used six ER(+)HER2(-) tumors and five triple negative (TN) tumors for a total of 11 tumors. Five PDX lines grew for an overall engraftment rate of 45%. We present our OS implantation method in detail. The re-transplantation rate of TN tumors in each transplant site was significantly higher in OS when compared to SQ tumors (70.1% vs. 32.1%, p < 0.01). OS tumors grow significantly faster than SQ tumors. Similarly, OS tumors demonstrated significantly more mitotic figures and Ki-67 positive cells than SQ tumors. The tumor re-transplantation rate significantly increased by the second and third generations with the OS method. The time from implantation to development of a palpable tumor dramatically decreased after the first passage. PDX of ER(+) tumors demonstrated significantly lower engraftment rates and slower tumor growth than TN tumors, which remarkably improved by the first passage. Orthotopically implanted PDX tumors showed better re-transplantation rates, greater tumor size, and more significant growth compared to the subcutaneously implanted model.

Estrogen Receptor Positive Breast Cancer with High Expression of Androgen Receptor has Less Cytolytic Activity and Worse Response to Neoadjuvant Chemotherapy but Better Survival.

Estrogen receptor (ER) positive breast cancer (BC), the most abundant BC subtype, is notorious for poor response to neoadjuvant chemotherapy (NAC). The androgen receptor (AR) was reported to support estradiol-mediated ER activity in an in vitro system. Recently, ER-positive BC with fewer tumor infiltrating lymphocytes (TILs) was shown to have a better prognosis, opposite to the trend seen with ER-negative BC. We hypothesized that ER-positive BC with high expression of AR will have fewer TILs and an inferior response to NAC, but with a better prognosis. In both TCGA and METABRIC cohorts, AR expression was significantly higher in ER-positive BCs compared to ER-negatives (p < 0.001, p < 0.001, respectively) and it correlated with ER expression (R = 0.630, R = 0.509, respectively). In ER-positive tumors, AR high tumors enriched UV response down (NES = 2.01, p < 0.001), and AR low tumors enriched DNA repair (NES = -2.02, p < 0.001). AR high tumors were significantly associated with procancer regulatory T-cells, and AR low tumors were associated with anticancer immune cells, such as CD4, CD8, and Gamma-Delta T-cells and memory B-cells in ER-positive BC (p < 0.01). Further, cytolytic activity was significantly lower in AR high BC in both cohorts. Finally, AR high tumors had a significantly lower rate of attaining pathological complete response to NAC (GSE22358), but better survival. In conclusion, our results demonstrated that high AR has fewer tumor infiltrating lymphocytes as well as cytolytic activity and an inferior response to NAC, but better survival in ER-positive BC.

Triple-Negative Breast Cancer with High Levels of Annexin A1 Expression Is Associated with Mast Cell Infiltration, Inflammation, and Angiogenesis.

Annexin A1 (ANXA1) is a phospholipid-linked protein involved in inflammation, immune response, and mast cell reactivity. Recently, we reported that ANXA1 is associated with aggressive features of triple-negative breast cancer (TNBC); however, its clinical relevance remains controversial. We hypothesized that human TNBC with high expression of ANXA1 mRNA is associated with pro-cancerous immune cell infiltration, including mast cells, and with an aggressive phenotype. Clinical and RNA-seq data were obtained from The Cancer Genome Atlas (TCGA, n = 1079) and Molecular Taxonomy of Breast Cancer International Consortium (METABRIC) (n = 1904). TNBC patients had significantly higher levels of ANXA1 expression compared to the other subtypes in both TCGA and METABRIC cohorts (p < 0.001). ANXA1 protein expression was assessed by immunohistochemistry in Japanese TNBC patient cohort (n = 48), where 17 cases (35.4%) had positive ANXA1 staining, and their overall survival was significantly shorter compared with negative staining group (p = 0.008). The CIBERSORT algorithm was used to calculate immune cell infiltrations. ANXA1 high tumors were associated with activated mast cells and M2 macrophages (p > 0.01), but did not show any association with tumor heterogeneity nor cytolytic activity. High expression of ANXA1 group enriched inflammation, epithelial-to-mesenchymal transition (EMT), and angiogenesis-related genes in a gene set enrichment assay in both cohorts. To our knowledge, this is the first study to demonstrate that ANXA1 is associated with infiltration of mast cells and inflammation that is associated with the aggressive phenotype of TNBC, such as EMT and angiogenesis.

[A Case of Synchronous Bilateral Neuroendocrine Ductal Carcinoma In Situ].

Neuroendocrine ductal carcinoma in situ(NE-DCIS)is a unique subtype of ductal carcinoma in situ(DCIS)that is not described in the general rules for clinical and pathological recording of breast cancer. NE-DCIS is described as an unusual variant of DCIS in the 2012 World Health Organization(WHO)classification. The chief complaint in NE-DCIS is hemorrhagic nipple discharge. The histological characteristics of NE-DCIS are solid growth of cancer cells with granular and spindle-shaped nuclei. Histologically, NE-DCIS is suggestive of low malignancy but a poor prognosis of neuroendocrine carcinoma of the breast has been reported. The report by Honami et al was the only other report of synchronous bilateral neuroendocrine ductal carcinoma in situ. We report the second case of NE-DCIS diagnosed synchronously in both breasts in a patient who had visited our outpatient clinic with hemorrhagic nipple discharge.

[A Case of Encapsulated Papillary Carcinoma of the Breast].

An 84-year-old woman was revealed to have focal asymmetric density(FAD)based on mammography, and ultrasonography showed a 0.5 cm sized cyst in the left breast. It gradually increased in size and contained solid components. A core needle biopsy revealed an intracystic papillary carcinoma of the breast. Partial mastectomy and sentinel lymph node biopsy were performed. Histopathological examination revealed an encapsulated papillary carcinoma and a papillary lesion surrounded by a thick fibrous capsule. Myoepithelial cells were not found at the periphery of the lesion or within fibrovascular cores. Currently, it is classified as non-invasive carcinoma, and the patient has a good prognosis.

[A Case of Occult Breast Cancer].

We report a case of occult breast cancer. A 61-years-old woman underwent tumorectomy of right axillary mass. Pathological diagnosis was adenocarcinoma. Two years after, right axillary mass was discovered again. Wide local excision, axillary lymph node dissection and radiation therapy of the breast was performed. Pathological findings showed lymph node metastasis of breast cancer, or primary cancer of the axially tail of the breast. Ten months after second operation, she presented an axillary mass again. She underwent resection of the axillary tumor. The pathological findings showed lymph node metastasis of breast cancer. There was no evidence of primary tumor of the breast during the period. We suspected lymph node metastasis of occult breast cancer. Irradiation was administered to the right axilla, and she is receiving endocrine therapy.

[A Case of Breast Carcinoma Associated with Osteoclast-Like Giant Cells].

Mammary carcinoma with osteoclast-like giant cells is uncommon, and its onset mechanism and malignancy are unknown. We report a case of mammary carcinoma with osteoclast-like giant cells. A 41-year-old woman noticed a lump in her left breast. Ultrasound sonography findings suggested breast cancer. A core needle biopsy revealed invasive ductal carcinoma of the breast. Modified radicalmastectomy and sentinell ymph node biopsy were performed. Histopathologicalexamination revealed papillotubular carcinoma with osteoclast-like giant cells. Cells were positive for estrogen receptor and progesterone, and negative for HER2. MIB-1 index was under 5%. The giant cells were generally associated with an inflammatory, fibroblastic, hyper-vascular stroma. The carcinomatous part of the lesion was most frequently a well-to moderately differentiated invasive ductalcarcinoma. Immunohistochemicaland ultrastructuralstudies suggested that the osteoclast-like giant cells were of stromalhistiocytic origin. To understand biochemicalfindings of this carcinoma, more case studies are required to be reported.

[Combination Therapy of Molecular-Targeted Drugs for Breast Cancer -- Their Potential in the Future].

In breast cancer treatment, molecular-targeted drugs such as trastuzumab and lapatinib have been used for many y ears, and the benefits have been seen in many patients. The molecular-targeted drugs have mainly been used in combination with cytotoxic agents; however, combination therapies with 2 molecular-targeted drugs are currently being investigated. The combination therapy of 2 HER2 receptor antibodies, pertuzumab and trastuzumab, has tremendous benefit for HER2 positive metastatic breast cancer patients. However, the combination of trastuzumab with tyrosine-kinase inhibitor lapatinib showed small benefits and its usage is limited. The combination of T-DM1 plus pertuzumab was not anymore effective than T-DM1 alone. The potentials of combined hormone therapies have been examined for ages. The combination of fulvestrant and aromatase inhibitor(AI)was shown to be beneficial in one phase III study; however, a conflicting result was reported by another large trial. To overcome hormone therapy resistance, the combinations of hormone therapy drugs with mTOR inhibitors(everolimus), pan-PI3K inhibitor(buparlisib), and CDK4/6 inhibitors(palbociclib, ribociclib, abemaciclib)are being investigated in various settings.

[Use of Pegfilgrastim in Adjuvant and Neoadjuvant Chemotherapy for Breast Cancer].

We assessed the incidence of febrile neutropenia(FN), infection, and relative dose intensity(RDI)with or without the use of pegfilgrastim in breast cancer patients receiving adjuvant or neoadjuvant chemotherapy. Twenty-five patients received 4 cycles of FEC(5-FU 500mg/m2 plus epirubicin 100 mg/m2 plus cyclophosphamide 100 mg/m2 q3w)followed by 4 cycles of docetaxel(75mg/m2 q3w). Ten patients were administered pegfilgrastim as primary prophylaxis throughout all cycles of chemotherapy, and 15 patients were not. The rate of FN was only 7% in patients not undergoing pegfilgrastim therapy. The infection rate and RDI were not significantly different between the 2 groups, but the incidence of fever was lower in patients treated with pegfilgrastim. In patients with early stage breast cancer, the use of primary pegfilgrastim during all chemotherapy cycles should be considered a safe option.

[A Case of Primary Poorly Differentiated/Small Cell Carcinoma of the Breast in a Patient with Von Recklinghausen's Disease].

We report a case of neuroendocrine carcinoma and poorly differentiated/small cell carcinoma ofthe breast in a patient with von Recklinghausen's disease. The patient was a 46-year-old woman who was diagnosed with von Recklinghausen's disease when she was 22 years old. She presented with left breast pain, and physical examination revealed a firm mass in the left breast. A core needle biopsy of the tumor revealed triple negative breast cancer with neuroendocrine features. We performed a simple mastectomy with lymph node dissection. We did not plan neoadjuvant chemotherapy because the tumor would be possibly inoperative if neoadjuvant chemotherapy was not effective for this neuroendocrine cancer. The tumor was diagnosed as a neuroendocrine carcinoma and poorly differentiated/small cell carcinoma. The patient was treated with CDDP and CPT- 11, which is a regimen often used to treat small cell lung cancer.

[A Case of Axillary Arterial Bleeding after Axillary Metastatic Lymph Node Necrosis during Treatment with Paclitaxel and Bevacizumabfor Breast Cancer].

A 44-year-old woman was diagnosed cT4bcN3cM1(LYM), Stage IV triple-negative breast cancer.Enhanced computed tomography revealed ipsilateral axillary lymph node metastasis, 10 cm in diameter.The supraclavicular and cervical lymph nodes also had metastases.She received paclitaxel(90mg/m2, on days 1, 8, and 15 every 4 weeks)in combination with bevacizumab(10mg/kg, on days 1 and 15 every 28 days).Her height was 165 cm, and her body weight was 100 kg.After 1 course of chemotherapy, a metastatic axillary lymph node with necrotic changes was removed spontaneously.A few days later, she experienced severe bleeding from her axillary artery, and she went into hypovolemic shock.Despite undergoing surgical hemostasis, the bleeding recurred twice, so we performed coil embolization of her subclavian artery.Thirty -five days after the first occurrence of bleeding, the patient died of sepsis and ARDS due to left arm necrosis.Bevacizumab is effective for the treatment of large tumors, but when the tumor is close to an artery, clinicians should be wary of fatal bleeding after necrosis.

Endosomal protein expression of γ1-adaptin is associated with tumor growth activity and relapse-free survival in breast cancer.

BACKGROUND: γ1-Adaptin is a subunit of adaptor protein complex-1 (AP-1), which regulates intracellular transport between the trans-Golgi network (TGN) and endosomes. Since expression levels of AP-1 subunits have been reported to be associated with cell proliferation and cancer malignancy, we investigated the relationships between the immunohistochemical expression of γ1-adaptin and both clinicopathological factors and relapse-free survival (RFS) in breast cancer tissue. MATERIALS AND METHODS: SK-BR-3 cell line depleted of γ1-adaptin was used for cell proliferation, migration, and invasion assay. Intracellular localization of γ1-adaptin was examined with immunohistochemistry (IHC) using an antibody against γ1-adaptin, and with double immunohistofluorescence (IHF) microscopy using markers for the TGN and endosome. γ1-Adaptin intensities in IHC samples from 199 primary breast cancer patients were quantified and assessed in relation to clinicopathological factors and RFS. RESULTS: Cell growth, migration, and invasion of SK-BR-3 cells were significantly suppressed by the depletion of γ1-adaptin. Although the staining patterns in the cancer tissues varied among cases by IHC, double IHF demonstrated that γ1-adaptin was mainly localized in EEA1-positive endosomes, but not in the TGN. γ1-Adaptin intensity was significantly higher in the tumor regions than in non-tumor regions. It was also higher in patients with Ki-67 (high), ER (-), PgR (-), and HER2 (+). Among subtypes of breast cancer, γ1-adaptin intensity was higher in HER2 than in luminal A or luminal B. The results of the survival analysis indicated that high γ1-adaptin intensity was significantly associated with worse RFS, and this association was also observed in group with ER (+), PgR (+), HER2 (-), Ki-67 (high), or luminal B. In addition, the Cox proportional hazards model showed that high γ1-adaptin intensity was an independent prognostic factor. CONCLUSION: These results suggest that the endosomal expression of γ1-adaptin is positively correlated with breast cancer malignancy and could be a novel prognostic marker.

[Myeloid-derived suppressor cells in patients with breast cancer].

Myeloid-derived suppressor cells (MDSC) are one of the major cell populations responsible for regulating immune responses. These cells have been reported to accumulate in the blood, lymph nodes, and tumor sites in most patients during tumor progression and in chronic infection. They are also reported to potently suppress T-cell functions. We studied MDSC in the peripheral blood mononuclear cells(PBMC)by flow cytometry using blood samples from 29 patients with breast cancer, and from 11 healthy donors. The cell level was significantly high for patients compared to the 11 healthy donors (5. 68±6. 09% vs. 0. 91±0. 54%). MDSC was significantly higher in all of the breast cancer patients (5. 68±6. 09%), preoperative patients (5. 79±4. 92%) and recurrent disease patients (5. 59±7. 28%), compared to healthy donors, but not for postoperative patients (1. 50±0. 95%). Thus, MDSC was elevated in patients with breast cancer, but decreased to the range of healthy individuals after the removal of the tumor mass. However, MDSC increased again with recurrence. We also report that in 2 cases, MDSC in the peripheral blood and pleural effusion of patients with metastatic breast cancer decreased after chemotherapy with gemcitabine.

Urine as a Source of Liquid Biopsy for Cancer.

Tissue biopsy is the gold standard for diagnosis and morphological and immunohistochemical analyses to characterize cancer. However, tissue biopsy usually requires an invasive procedure, and it can be challenging depending on the condition of the patient and the location of the tumor. Even liquid biopsy analysis of body fluids such as blood, saliva, gastric juice, sweat, tears and cerebrospinal fluid may require invasive procedures to obtain samples. Liquid biopsy can be applied to circulating tumor cells (CTCs) or nucleic acids (NAs) in blood. Recently, urine has gained popularity due to its less invasive sampling, ability to easily repeat samples, and ability to follow tumor evolution in real-time, making it a powerful tool for diagnosis and treatment monitoring in cancer patients. With the development and advancements in extraction methods of urinary substances, urinary NAs have been found to be closely related to carcinogenesis, metastasis, and therapeutic response, not only in urological cancers but also in non-urological cancers. This review mainly highlights the components of urine liquid biopsy and their utility and limitations in oncology, especially in non-urological cancers.

Octogenarians' Breast Cancer Is Associated with an Unfavorable Tumor Immune Microenvironment and Worse Disease-Free Survival.

Elderly patients are known to have a worse prognosis for breast cancer. This is commonly blamed on their medical comorbidities and access to care. However, in addition to these social issues, we hypothesized that the extreme elderly (octogenarians-patients over 80 years old) have biologically worse cancer with unfavorable tumor immune microenvironment. The Cancer Genomic Atlas (TCGA) and the Molecular Taxonomy of Breast Cancer International Consortium (METABRIC) breast cancer cohorts were analyzed. The control (aged 40-65) and octogenarians numbered 668 and 53 in TCGA and 979 and 118 in METABRIC, respectively. Octogenarians had significantly worse breast cancer-specific survival in both cohorts (p < 0.01). Octogenarians had a higher ER-positive subtype rate than controls in both cohorts. Regarding PAM50 classification, luminal-A and -B subtypes were significantly higher in octogenarians, whereas basal and claudin-low subtypes were significantly lower (p < 0.05) in octogenarians. There was no difference in tumor mutation load, intratumor heterogeneity, or cytolytic activity by age. However, the octogenarian cohort was significantly associated with high infiltration of pro-cancer immune cells, M2 macrophage, and regulatory T cells in both cohorts (p < 0.05). Our results demonstrate that octogenarians' breast cancer is associated with worse survival and with an unfavorable tumor immune microenvironment.

Altered Expression of Secreted Mediator Genes That Mediate Aggressive Breast Cancer Metastasis to Distant Organs.

Heterogeneity is the characteristic of breast tumors, making it difficult to understand the molecular mechanism. Alteration of gene expression in the primary tumor versus the metastatic lesion remains challenging for getting any specific targeted therapy. To better understand how gene expression profile changes during metastasis, we compare the primary tumor and distant metastatic tumor gene expression using primary breast tumors compared with its metastatic variant in animal models. Our RNA sequencing data from cells revealed that parental cell and the metastatic variant cell are different in gene expression while gene signature significantly altered during metastasis to distant organs than primary breast tumors. We found that secreted mediators encoding genes (ANGPTL7, MMP3, LCN2, S100A8, and ESM1) are correlated with poor prognosis in the clinical setting as divulged from METABRIC and TCGA-BRCA cohort data analysis.

Novel Breast Cancer Brain Metastasis Patient-Derived Orthotopic Xenograft Model for Preclinical Studies.

The vast majority of mortality in breast cancer results from distant metastasis. Brain metastases occur in as many as 30% of patients with advanced breast cancer, and the 1-year survival rate of these patients is around 20%. Pre-clinical animal models that reliably reflect the biology of breast cancer brain metastasis are needed to develop and test new treatments for this deadly condition. The patient-derived xenograft (PDX) model maintains many features of a donor tumor, such as intra-tumor heterogeneity, and permits the testing of individualized treatments. However, the establishment of orthotopic PDXs of brain metastasis is procedurally difficult. We have developed a method for generating such PDXs with high tumor engraftment and growth rates. Here, we describe this method and identify variables that affect its outcomes. We also compare the brain-orthotopic PDXs with ectopic PDXs grown in mammary pads of mice, and show that the responsiveness of PDXs to chemotherapeutic reagents can be dramatically affected by the site that they are in.