Enhanced efficacy of radioimmunotherapy combined with systemic chemotherapy and local hyperthermia in xenograft model

Intraperitoneal radioimmunotherapy to treat the early phase of peritoneal dissemination of human colon cancer cells in a murine model

BACKGROUND AND AIM

In patients with a high risk of peritoneal dissemination of colon cancer, a treatment adjuvant to surgical resection would improve their prognosis. We aimed to determine whether radioimmunotherapy employing radiolabelled monoclonal antibody would work in this situation.

METHODS

A murine model of peritoneal dissemination was established in female Balb/c nu/nu mice by intraperitoneal injection of LS180 human colon cancer cells. Radioimmunotherapy with 7.4 MBq of a murine IgG1, anti-colorectal A7 monoclonal antibody, radiolabelled with (131)I by the chloramine-T method was conducted intraperitoneally on days 0, 3, 7 and 14 after cell inoculation, respectively.

RESULTS

Radioimmunotherapy at any timing improved survival of mice as compared with those of non-treated mice and mice treated with a daily dose of 30 mg x kg(-1) of 5-fluorouracil for 4 consecutive days. The best improvement was obtained when radioimmunotherapy was conducted on day 0.

CONCLUSION

These results indicate that intraperitoneal radioimmunotherapy may effectively kill colon cancer cells disseminated in the peritoneal cavity before formation of tumours and, therefore, may work as an adjuvant treatment to prevent peritoneal metastasis of colon cancer.

Radioimmunotherapy of human colon cancer xenografts by using 131I labeled-CAb1 F(ab')2

PURPOSE

Therapeutic efficacy, suitable dose, and administration times of 131I-CAb1 F(ab')2, a new monoclonal antibody therapeutics specifically directed against a cell surface-associated glycoprotein of colon cancer, were investigated in this article.

METHODS AND MATERIALS

In human colon cancer xenografts, 131I-CAb1 F(ab')2 at the dose of 125 muCi, 375 muCi, and 1125 muCi were administrated intraperitoneally on Days 6 and 18 after implantation of HR8348 cells with CAb1 high reactivity. Survival time and tumor growth inhibition rate were used to evaluate the efficacy and safety of 131I-CAb1 F(ab')2 in treatment of colon cancer xenografts.

RESULTS

Treatment of 125, 375, and 1125 muCi 131I-CAb1 F(ab')2 did not significantly decrease the mean survival time of nude mice when compared with nontreated groups (p = 0.276, 0.865, 0.582, respectively). Moreover, the mean survival times of nude mice receiving 375 muCi and 1125 muCi 131I-CAb1 F(ab')2 were significantly longer than that of 5-FU-treated groups (p = 0.018 and 0.042). Tumor growth inhibition rates of the first therapy were 35.67% and 41.37%, with corresponding 131I-labeled antibody dosage of 375 muCi and 1125 muCi. After single attack dosage, second reinforcement therapy may rise efficacy significantly. Tumor growth inhibition rates of 125 muCi, 375 muCi, and 1125 muCi 131I-labeled antibody on Day 20 posttherapy were 42.65%, 56.56%, and 84.41%, respectively. Histopathology examination revealed that tissue necrosis of various degrees was found in 131I-CAb1 F(ab')2-treated groups.

CONCLUSION

131I-CAb1 F(ab')2 is safe and effective for colon cancer. It may be a novel and potentially adjuvant therapeutics for colon cancer.

Comparative animal models for the study of lymphohematopoietic tumors: strengths and limitations of present approaches

The lymphomas probably represent the most complex and heterogenous set of malignancies known to cancer medicine. Underneath the single term lymphoma exist some of the fastest growing cancers known to science (i.e Burkitt's and lymphoblastic lymphoma), as well as some of the slowest growing (i.e. small lymphocytic lymphoma [SLL] and follicular lymphoma). It is this very biology that can dictate the selection of drugs and treatment approaches for managing these patients, strategies that can range from very aggressive combination chemotherapy administered in an intensive care unit (for example, patients with Burkitt's lymphoma), to watch and wait approaches that may go on for years in patients with SLL. This impressive spectrum of biology emerges from a relatively restricted number of molecular defects. The importance of these different molecular defects is of course greatly influenced by the intrinsic biology that defines the lymphocyte at its different stages of differentiation and maturation. It is precisely this molecular understanding that is beginning to form the basis for a new approach to thinking about lymphoma, and novel approaches to its management. Unfortunately, while our understanding of human lymphoma has blossomed, our ability to generate appropriate animal models reflective of this biology has not. Most preclinical models of these diseases still rely upon sub-cutaneous xenograft models of only the most aggressive lymphomas like Burkitt's lymphoma. While these models clearly serve an important role in understanding biology, and perhaps more importantly, in identifying promising new drugs for these diseases, they fall short in truly representing the broader, more heterogenous biology found in patients. Clearly, depending upon the questions being posed, or the types of drugs being studied, the best model to employ may vary from situation to situation. In this article, we will review the numerous complexities associated with various animal models of lymphoma, and will try to explore several alternative models which might serve as better in vivo.

Optimization of radioimmunotherapy interactions with hyperthermia

The efficacy of radioimmunotherapy (RIT) employing radiolabelled monoclonal antibodies (MAb) is currently limited in most solid tumours. The combination of local hyperthermia (HT) with RIT has the potential to enhance tumour targeting of MAb; moreover, this approach may add an antitumour effect to radioresistant hypoxic and S-phase cells and may inhibit the cells from repairing sublethal damage or potentially lethal damage caused by ionizing radiation. There are distinct types of protocols in this combination. Hyperthermic temperature and timing relative to RIT administration appear to affect the efficacy of the combination therapy. Responses to heating at any particular condition are not always the same among different tumour types. There are many papers describing influence of HT on the biodistribution of radiolabelled MAb, but only limited information is currently available on 'therapeutic' outcomes regarding the dependency of combination protocols. A previous study suggested that the best therapeutic improvement would be achieved when HT was combined immediately after the administration of MAb, which significantly increases the radiation absorbed dose to tumours and produces a uniform intratumoural dose distribution. Further therapeutic investigation should be required to reach the optimal protocol of combining these two modalities.

Combined 90Yttrium-DOTA-labeled PAM4 antibody radioimmunotherapy and gemcitabine radiosensitization for the treatment of a human pancreatic cancer xenograft

We have examined the application of (90)Y-DOTA-cPAM4, anti-MUC1 IgG, in combination with the front-line drug gemcitabine as a potential therapeutic for pancreatic cancer. Athymic nude mice bearing CaPan1 human pancreatic cancer xenografts were administered 2 mg of gemcitabine on days 0, 3, 6, 9 and 12 with concurrent (90)Y-DOTA-cPAM4 (100 microCi) provided on day 0. A second group of mice received a second cycle of treatment 5 weeks after the start of the first cycle. Control groups of mice included those that received either treatment arm alone, the combined modality treatment employing a nontargeting control antibody (hLL2, anti-B-cell lymphoma) and a final group that was left untreated. Gemcitabine administered as a single agent provided no antitumor effect. A single cycle of the combined (90)Y-DOTA-cPAM4 and gemcitabine treatment provided greater inhibition of tumor growth than was observed for any of the other treatment procedures. Tumor growth was delayed for a period of 7 weeks. Two cycles of gemcitabine with concomitant (90)Y-DOTA-cPAM4 yielded significant tumor regression and increased median survival to 21 weeks vs. 12 weeks for mice receiving a single cycle of therapy (p<0.024). Median tumor volume doubling-times were 18 weeks in mice treated with 2-cycles of therapy vs. 7 weeks in mice given only 1-cycle (p<0.001), and 3.5 weeks for the group that received 2-cycles of gemcitabine concomitant with equitoxic nontargeting (90)Y-DOTA-hLL2 (p<0.001). These data suggest that addition of (90)Y-DOTA-cPAM4 RAIT to a gemcitabine treatment regimen may provide enhanced antitumor efficacy for the treatment of pancreatic cancer.

Intraperitoneal radioimmunotherapy in treating peritoneal carcinomatosis of colon cancer in mice compared with systemic radioimmunotherapy

Peritoneal spread is one of major causes of mortality in colorectal cancer patients. In the current investigation, the efficacy of radioimmunotherapy (RIT) with i.p. administration of an anti-colorectal cancer IgG1, 131I-A7, was compared to that with i.v. administration in BALB/c female mice bearing peritoneal nodules of LS180 human colon cancer cells, at the same toxicity level. Distribution of either i.p. or i.v. administered 131I-A7 and i.p. administered irrelevant 131I-HPMS-1 was assessed. Based on the results of toxicity determination at increments of 2 MBq and estimated dosimetry, an i.p. dose of 11 MBq and an i.v. dose of 9 MBq were chosen for treatment. Mice were monitored for long-term survival: untreated mice (n = 11), mice undergoing i.p. RIT with 131I-A7 (n = 11), mice undergoing i.v. RIT with 131I-A7 (n = 11) and mice undergoing non-specific i.p. RIT with 131I-HPMS-1 (n = 5). Intraperitoneal injection of 131I-A7 produced faster and greater tumor accumulation than i.v. injection: 34.2 +/- 16.5% of the injected dose per g (% ID/g) and 11.1 +/- 3.6% ID/g at 2 h, respectively (P < 0.0001). Consequently, cumulative radioactivity in tumors was 1.73-fold higher with i.p. injection. 131I-HPMS-1 did not show specific accumulation. Non-specific RIT with 131I-HPMS-1 (mean survival, 26.0 +/- 2.5 days) did not affect the survival as compared to no treatment (26.7 +/- 1.9 days). Intravenous RIT with 131I-A7 prolonged the survival of mice to 32.8 +/- 1.8 days (P < 0.01). Intraperitoneal RIT with 131I-A7 improved the survival more significantly and attained cure in 2 of 11 mice (P < 0.05 vs. i.v. RIT). In conclusion, i.p. RIT is more beneficial in treating peritoneal carcinomatosis of colon cancer than i.v. RIT in a murine model.