Table 1.

Representative examples of BCG applications and key findings in the field of tumor immunotherapy.

BCG strain/ formulation	Publication year	Host	Application	Key finding(s)	Ref.
Phipps	1959	Female Ha/ICR Swiss mice and C57 hybrid mice	Infection of mice by intravenous injection of BCG	It is one of the earliest reports to show that BCG-infected mice are resistant to tumor growth. Tumors were inoculated (either subcutaneously or intraperitoneally) after BCG infection was established.	[124]
Phipps	1971	Male Guinea Pigs	Intradermal injection of BCG into tumors pre-established intradermally in Guinea pigs. Guinea pigs were either BCG-immunized or un-immunized.	This study showed that intratumoral injection of BCG caused complete regression of tumors in most animals and inhibited metastasis to drainage lymph nodes. Effect was noticeable in both BCG-pre-immunized and un-immunized Guinea pigs. Contact between tumor cells and injected BCG seemed to be crucial.	[66]
Tice	1975	One human patient with metastatic malignant melanoma in the urinary bladder.	A whole ampoule of a market available BCG was intratumorally injected at the base of a 2 cm metastatic melanoma lesion in the bladder using a cystoscopic needle.	This study shows that a 2 cm metastatic melanoma tumor lesion inside the bladder completely disappeared 1 week following intratumoral injection of BCG. Metastatic melanoma was spread later to the small intestine and liver, and the patient died later. However, no evidence of bladder metastasis recurrence was found.	[67]
Tice	1975	Mongrel dogs	BCG was applied to bladder either by intramucosal injection into the exposed bladder or inoculation into the bladder using a catheter.	BCG inoculation into the bladder of PPD-sensitized dogs seemed to be well-tolerated, which suggested potential for BCG use in bladder cancer.	[125]
Glaxo	1970	36 human patients with subcutaneous melanoma	Intralesional injection of BCG	About 91% of injected melanoma lesions disappeared or showed regression. About 20% of patients showed regression of un-injected lesions that are located within the same drainage area of injected lesions.	[65]
Montreal	1976	9 human patients with superficial bladder cancer	Intravesical instillations of BCG into the bladder	This is the first clinical study that reports the use of intravesical instillation of BCG in bladder cancer. Recurrence of the disease in the patients treated was reduced.	[79]
Pasteur	1990	C3H/HEN mice.	Intravesical instillation of BCG into the bladder	It was found that fibronectin-mediated attachment of BCG to the bladder mucosa was crucial to elicit the desired antitumor activity. This was an important step towards elucidating the mechanism underlying the BCG immunotherapeutic activity in bladder cancer.	[70]
Connaught	2000	Human patients with resected bladder tumors with high risk of recurrence	Maintenance schedule of BCG instilled intravesically and given percutaneously for up to 36 months.	This is one of the earliest large clinical trials that showed the benefit of a maintenance schedule as compared to the standard induction therapy alone in bladder cancer patients.	[36]
Connaught and Tice	2014	142 human patients with NMIBC.	6 intravesical instillations of BCG into the bladder	By comparing 2 commercially available BCG strains, the researchers reported improved recurrence-free survival by the Connaught strain. The genetic difference between the strains may explain the survival advantage.	[176]

BCG: bacillus Calmette-Guerin; PPD: purified protein derivative; NMIBC: non-muscle invasive bladder cancer.