Cryoablation of human colorectal cancer in vivo in a nude mouse xenograft model

Breast Cancer Cryoablation: Assessment of the Impact of Fundamental Procedural Variables in an In Vitro Human Breast Cancer Model

INTRODUCTION

Breast cancer is the most prominent form of cancer and the second leading cause of death in women behind lung cancer. The primary modes of treatment today include surgical excision (lumpectomy, mastectomy), radiation, chemoablation, anti-HER2/neu therapy, and/or hormone therapy. The severe side effects associated with these therapies suggest a minimally invasive therapy with fewer quality of life issues would be advantageous for treatment of this pervasive disease. Cryoablation has been used in the treatment of other cancers, including prostate, skin, and cervical, for decades and has been shown to be a successful minimally invasive therapeutic option. To this end, the use of cryotherapy for the treatment of breast cancer has increased over the last several years. Although successful, one of the challenges in cryoablation is management of cancer destruction in the periphery of the ice ball as the tissue within this outer margin may not experience ablative temperatures. In breast cancer, this is of concern due to the lobular nature of the tumors. As such, in this study, we investigated the level of cell death at various temperatures associated with the margin of a cryogenic lesion as well as the impact of repetitive freezing and thawing methods on overall efficacy.

METHODS

Human breast cancer cells, MCF-7, were exposed to temperatures of -5°C, -10°C, -15°C, -20°C, or -25°C for 5-minute freeze intervals in a single or repeat freeze-thaw cycle. Samples were thawed with either passive or active warming for 5 or 10 minutes. Samples were assessed at 1, 2, and 3 days post-freeze to assess cell survival and recovery. In addition, the modes of cell death associated with freezing were assessed over the initial 24-hour post-thaw recovery period.

RESULTS

Exposure of MCF-7 cells to -5°C and -10°C resulted in minimal cell death regardless of the freeze/thaw conditions. Freezing to a temperature of -25°C resulted in complete cell death 1 day post-thaw with no cell recovery in all freeze/thaw scenarios evaluated. Exposure to a single freeze event resulted in a gradual increase in cell death at -15°C and -20°C. Application of a repeat freeze-thaw cycle (dual 5-minute freeze) resulted in an increase in cell death with complete destruction at -20°C and near complete death at -15°C (day 1 survival: single -15°C freeze/thaw = 20%; repeated -15°C freeze/thaw = 4%). Analysis of thaw interval time (5 vs 10 minute) demonstrated that the shorter 5-minute thaw interval between freezes resulted in increased cell destruction. Furthermore, investigation of thaw rate (active vs passive thawing) demonstrated that active thawing resulted in increased cell survival thereby less effective ablation compared with passive thawing (eg, -15°C 5/10/5 procedure survival, passive thaw: 4% vs active thaw: 29%).

CONCLUSIONS

In summary, these in vitro findings suggest that freezing to temperatures of 25°C results in a high degree of breast cancer cell destruction. Furthermore, the data demonstrate that the application of a repeat freeze procedure with a passive 5-minute or 10-minute thaw interval between freeze cycles increases the minimal lethal temperature to the -15°C to -20°C range. The data also demonstrate that the use of an active thawing procedure between freezes reduces ablation efficacy at temperatures associated with the iceball periphery. These findings may be important to improving future clinical applications of cryoablation for the treatment of breast cancer.

Immunological response to renal cryoablation in an in vivo orthotopic renal cell carcinoma murine model

PURPOSE

The immunological consequences of cryoablation for renal cell carcinoma are largely unknown. Cryoablation is an attractive therapeutic option for tumors due to its minimally invasive nature. Cryoablation is also potentially immunogenic. We describe the development of an animal model to deliver in vivo renal cryotherapy to orthotopically implanted renal cell carcinoma and the results of multiple immunological interrogations after cryoablation.

MATERIALS AND METHODS

Four to 6-week-old female Balb/c mice (Jackson Laboratories, Bar Harbor, Maine) underwent renal subcapsular implantation of the syngeneic murine renal cell carcinoma Renca. Two weeks later contact cryoablation was done in tumor bearing kidneys. Another group of animals underwent cryoablation of normal kidneys. Animals were sacrificed 2 weeks after tumor injection or 1 and 2 weeks after cryoablation, respectively. Kidneys, spleens and draining lymph nodes were harvested. Evaluation consisted of immunohistochemistry, immunofluorescence and gene expression profiling using reverse-transcriptase polymerase chain reaction.

RESULTS

Subcapsular tumor implantation was successful in all cases and confirmed histologically. No significant lymphocytic infiltrate was seen in tumor only animals but those treated with cryoablation (tumor and nontumor bearing) had a significant inflammatory response primarily in sublethal tissue injury and perivascular areas. After cryoablation most infiltrating cells were neutrophils, macrophages and T cells. Polymerase chain reaction showed increased interferon-gamma production in kidneys after cryoablation.

CONCLUSIONS

This study shows the potential feasibility of this animal model for studying cryo-immunology. We confirm the absence of any significant immune cell infiltration in tumor bearing kidneys and report a significant inflammatory infiltrate after cryoablation, consisting primarily of neutrophils, macrophages, and CD4+ and CD8+ T cells with an increase in the T helper type 1/2 ratio. This orthotopic murine model can form the basis of future studies of additional immunological aspects of renal cryoablation.

Cryosurgery during topical imiquimod: a successful combination modality for lentigo maligna

BACKGROUND

Either cryosurgery or topical imiquimod have been used to treat patients with lentigo maligna in cases where surgery is not feasible.

METHODS

We report a patient with lentigo maligna, who was treated with the combination of topical imiquimod and cryosurgery, and review the rationale, which led us to design the present combined cryo-immunological treatment modality.

RESULTS

Sustained clearance of lentigo maligna to date (26 months after treatment). The successful treatment of this patient was based on the following rationale: A cryosurgery session during continuing imiquimod application may: (i) reinforce apoptosis of tumor cells; (ii) strengthen antiangiogenesis in the treated tumor; and (iii) build-up a potent tumor-destructive immune response by a cascade of events starting with imiquimod-promoted attraction of immature dendritic antigen-presenting cells (DCs) into the tumor. DCs further mature within the tumor-antigen-rich environment of subsequently cryo-destructed tumor and upon imiquimod-driven migration into the peripheral lymph nodes can stimulate a specific antineoplastic cell-mediated immunity. Finally, continuing imiquimod application after cryosurgery may increase recruitment of activated effector cells into the tumor tissue leading to its destruction.

CONCLUSION

Cryosurgery during continued topical imiquimod seems to be a promising treatment for lentigo maligna.

Cryotherapy for liver tumors: current status, perspectives, clinical results, and review of literature

Cryotherapy has gained importance as a locally ablative treatment option for patients with non-resectable liver tumors, especially metastases from colorectal cancer. We have used this technique since 1996 for the treatment of 77 patients with malignant liver tumors. Patient data was prospectively recorded and follow-up was until September 2002 or death. Fifty-five patients had colorectal cancer liver metastases, 16 metastases from other primaries and 6 had hepatoma. Forty patients had cryotherapy only and 37 had an additional liver resection. Morbidity and mortality were 22% and 1.3%, respectively. In 68% of patients with colorectal liver metastases and an elevated serum carcinoembryonic antigen-level preoperatively, it returned to the normal range following cryosurgery. For all 77 patients, median survival was 28 months with a 3- and 5-year-survival rate of 39% and 26%, respectively, and median survival was 29 months with a 3- and 5-year-survival rate of 44% and 26%, respectively, for the 55 patients with colorectal liver metastases. Local recurrence at the cryosite was observed in 13 of 65 patients (20%) with initially complete treatment. For cryotherapy to further establish as a treatment for malignant liver tumors in a time where many new local ablative techniques are developing, different goals need to be achieved. The trauma of the procedure and local treatment failure need to be minimized and survival results need to be optimized. Published studies and new possible fields of research regarding these goals are discussed.

Apoptosis induced by cryo-injury in human colorectal cancer cells is associated with mitochondrial dysfunction

Cryotherapy, a method of in situ ablation, is used in the treatment of colorectal liver metastases with variable results. During the treatment, the central area of treated tumor undergoes necrotic destruction by lethal cryo-injury; however, the cellular response of tumor exposed to sublethal cryo-injury at the peripheral zone is unclear. In our study, we have identified the induction of apoptosis by cryo-injury at -10 degrees C in 4 colorectal cancer cell lines (HT29, HCT116, KM12C and KM12SM). The apoptosis was characterized by chromatin condensation, transferase-mediated dUTP nick end-labeling (TUNEL) staining, proteolytic cleavage of poly(ADP-ribose) polymerase (PARP) and cytokeratin 18, and activation of caspase-3. The occurrence and intensity of cryo-induced apoptosis did not correlate with the functional status of p53 in the cell lines studied. The expression of anti-apoptotic proteins (Bcl-2, Bcl-X(L)) and pro-apoptotic proteins (Bax, Bcl-X(S), Bad, and Bak) in response to cryo-injury varied in this cell line panel. The basal level of Bcl-2/Bax protein ratio correlated inversely to the apoptotic rate. We further demonstrated that Bax level decreased in cytosol and increased in mitochondria, followed by a loss of mitochondrial membrane potential after cryo-injury in HT29 cells. These findings indicate that cryo-injury induces apoptosis in colorectal cancer cells via disruption of mitochondrial integrity. The cryo-induced apoptosis was also identified in a nude mouse tumor xenograft model. Our elucidation of the apoptosis pathway induced by cryo-injury implies that synergistic combination of cryosurgery with pharmacological agents that augment of apoptosis induction may have clinical relevance in treating colorectal liver metastasis.